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Nanofiltration, bipolar electrodialysis and reactive extraction hybrid system for separation of fumaric acid from fermentation broth
Bioresource Technology 167 (2014) 219–225
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Nanofiltration, bipolar electrodialysis and reactive extraction hybrid system for separation of fumaric acid from fermentation broth Krystyna Prochaska ⇑, Katarzyna Staszak, Marta Joanna Woz´niak-Budych, Magdalena Regel-Rosocka, Michalina Adamczak, Maciej Wis´niewski, Jacek Staniewski ´ , Poland Poznan University of Technology, Institute of Chemical Technology and Engineering, pl. M. Skłodowskiej-Curie 2, 60-965 Poznan
h i g h l i g h t s Hybrid system for fumaric acid recovery from fermentation broth is proposed. The system involves nanofiltration, bipolar electrodialysis and reactive extraction. Fumaric salts can be efficiently concentrated in nanofiltration process. Bipolar electrodialysis allows selective separation of fumaric acid. Three-step extraction of fumaric acid with Aliquat 336 and Cyanex 923 is efficient.
a r t i c l e
i n f o
Article history: Received 17 April 2014 Received in revised form 2 June 2014 Accepted 4 June 2014 Available online 11 June 2014 Keywords: Nanofiltration Reactive extraction Bipolar electrodialysis Fumaric acid Fermentation broth
a b s t r a c t A novel approach based on a hybrid system allowing nanofiltration, bipolar electrodialysis and reactive extraction, was proposed to remove fumaric acid from fermentation broth left after bioconversion of glycerol. The fumaric salts can be concentrated in the nanofiltration process to a high yield (80–95% depending on pressure), fumaric acid can be selectively separated from other fermentation components, as well as sodium fumarate can be conversed into the acid form in bipolar electrodialysis process (stack consists of bipolar and anion-exchange membranes). Reactive extraction with quaternary ammonium chloride (Aliquat 336) or alkylphosphine oxides (Cyanex 923) solutions (yield between 60% and 98%) was applied as the final step for fumaric acid recovery from aqueous streams after the membrane techniques. The hybrid system permitting nanofiltration, bipolar electrodialysis and reactive extraction was found effective for recovery of fumaric acid from the fermentation broth. Ó 2014 Elsevier Ltd. All rights reserved.
1. Introduction Organic acids are mainly produced by microbial fermentation (Deng et al., 2012) resulting in generation of fermentation broth containing organic salts and some impurities like sugars and mineral salts. In fact, many operations are necessary to separate and purify the final product (organic acid) from the fermentation broth. For example fumaric acid can be produced by fermentation in the presence of Escherichia coli species (Song et al., 2013). It was found that under aerobic conditions E. coli were able to produce 28 g/L of fumaric acid, however, during bacterial fermentation a substantial amount of acetic acid was formed. Nakajima-Kambe et al. (1997) tested the influence of temperature, pH and type of carbon sources ⇑ Corresponding author. Tel.: +48 61 665 3601; fax: +48 61 665 3649. E-mail address: [email protected] (K. Prochaska). http://dx.doi.org/10.1016/j.biortech.2014.06.010 0960-8524/Ó 2014 Elsevier Ltd. All rights reserved.
(such as maleic, malonic, itaconic, adicipic and succinic acids) on the rate of the bioconversion. The highest fumaric acid productivity was obtained in the temperature range between 30 and 45 °C, at pH 7 and with maleic acid used as a carbon source. Under these conditions, above 40 g/L of fumaric acid and almost threefold less of L-malic acid, as a by-product, were obtained after 6 h of incubation. Xu et al. (2010) have reported that fumaric acid could be produced from two-stage utilization of corn straw in the presence of Rhizopus oryzae strain. The xylose-rich hydrolysates obtained as a result of acid hydrolysis of corn straw, were responsible for the growth of microorganisms. The corn straw left after acid hydrolysis was used in the next step for fumaric acid production in glucoserich hydrolysates upon enzymatic hydrolysis. Under the optimal conditions the fumaric acid production reached up to 28 g/L. The protoplast fusion of R. oryzae and Rhizopus microsporus strains for fumaric acid production from glycerol was proposed by
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Kordowska-Wiater et al. (2012). It was shown that double fusion led to an increase in fumaric acid productivity in relation to the parental strains. Fermentation of glycerol as the only carbon source in the medium, resulted in formation of small amounts of lactic acid and around 30 g/L of fumaric acid. These reports imply that many additional operations are necessary to separate and purify the major product (an organic acid) from the broth. Da Silva and Miranda (2013) have suggested the application of adsorption/ desorption on activated carbon and a weak base resin for the recovery of an organic acid from the broth. Zhang et al. (2012) have proposed a two-stage crystallization to extract glutamic acid from fermentation broth. By means of the proposed technique, glutamic acid was recovered in 83% in the first stage including isoelectric crystallization, while more than 70% of the remaining glutamic acid was separated in the second stage by evaporative crystallization. One of the techniques commonly used to purify organic acids from the broth is esterification. In other reports, Zhao et al. (2009) have presented the possibilities of lactic acid recovery from fermentation broth of kitchen garbage by esterification and hydrolysis. The process was carried out in two steps: first, lactate ester was produced by esterification of ammonium lactate of 96% yield, and then the lactate ester was purified and hydrolyzed to lactic acid in the presence of a cation-exchange resin. In this investigation, a hybrid system consisting of three stages of nanofiltration (NF), bipolar electrodialysis (EDBM) and reactive extraction was proposed for separation of fumaric acid from the fermentation broth left after bioconversion of glycerol (Fig. 1). At first, nanofiltration was performed as a pre-treatment step to concentrate organic acids and separate glycerol from the other components of the broth. Two types of devices were used at the nanofiltration stage: a laboratory setup equipped with a flat sheet polymeric membrane, and a pilot scale NF system equipped with a tubular ceramic membrane (Staszak et al., 2014). At the second stage, bipolar electrodialysis of the nanofiltration retentate, containing concentrated organic acids, was carried out, and after that reactive extraction of the nanofiltration retentate and diluate after bipolar electrodialysis were used to recover the residues of fumaric acid. 2. Methods 2.1. Materials Two fermentation broths of different compositions coming from biotechnological conversion of glycerol were investigated. The research material was delivered by one of the collaborators in the frames of the project: ‘‘Biotechnological conversion of glycerol to polyols and dicarboxylic acids.’’ The method of fermentation is protected by the copyright (Kordowska-Wiater et al., 2012).
Various solvating (tributyl phosphate – TBP, mixture of trialkylphosphine oxides – Cyanex 923) or basic (trioctylamine – TOA, methyltrioctylammonium chloride – Aliquat 336) extractants were used as received to prepare 0.1 mol/L organic solutions of extractant in octanol. 2.2. Nanofiltration experiments A laboratory setup SEPA Osmonics (GE Osmonics, USA) with polymeric flat sheet membrane (Koch Membrane System, UK) was used. The properties of the membrane used in this study are: cut off 200 Da, effective surface area 0.0155 m2, pH range: 0–14. Hydrodynamic coefficient was experimentally measured using demineralized water at 25 °C and was equal to 0.021 L/m2 h MPa. All processes of nanofiltration were performed at 25 ± 1 °C and transmembrane pressure (TMP) in the 0.8–1.4 MPa range. Prior to all the experiments, the initial flux of water at a specified transmembrane pressure was tested. After each experiment, the nanofiltration modules were cleaned with water until the initial water flux was recovered. During nanofiltration 3 L of solution from the feed vessel was pumped to the membrane module, and the retentate was circulated in a closed loop with a volume flow of 160 L/h (0.7 m/s). Experiments were performed for no longer than 2 h. Moreover, the results of nanofiltration experiments were compared with those described in the previous work (Staszak et al., 2014) in which the pilot scale nanofiltration module with monochannel tubular ceramic membrane was used. 2.3. Bipolar electrodialysis experiments Three-chamber laboratory ED setup with a stack consisting of bipolar (PC 200bip) and anion-exchange (PC 200D) membranes produced by PCCell GmbH separated by 10 mm polycarbonate spacers, was used in this study. The effective surface area of membrane stack was equal to 0.0064 m2. The electrodialysis stack was connected with a peristaltic pump (Verder), DC power supply (NDN) and a multifunction meter (Elmetron) measuring the pH, the conductivity and the temperature of working solutions. The anode was made of titanium plated with iridium and the cathode was made of steel 314. Bipolar electrodialysis process was performed at 25 ± 1 °C under constant electric field conditions at 120 A/m2 of current density. Experiments were conducted until a constant value of conductivity was obtained. The working solution containing fumaric salts was fed to the diluate chamber and the solution with fumaric acid instead of water (to reduce the overall resistance) was introduced to the concentrate chamber. In the electrode chambers, sodium sulfate
Fig. 1. Hybrid system for separation of fumaric acid from fermentation broth.
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solution was placed to ensure current transport during the process. The applied constant electric field initiated the transport of fumarate anions through the anion-exchange membrane to the concentrate chamber and in the same time the formation of H+ and OH ions in the transition region of bipolar membrane. In fact, fumaric anions and hydrogen ions enter the concentrate chamber forming fumaric acid. The stack configuration used in this investigation can be applied to convert organic salts into organic acids. 2.4. Reactive extraction experiments Reactive extraction of the solutions studied was carried out in a typical way: the aqueous feed was mechanically shaken with the same volume of the organic phase for 30 min at 25 °C in glass separatory funnels, and then allowed to stand for phase separation. The influence of pH on fumaric acid extraction with various solvating extractant solutions was investigated. Reactive extraction of the solutions resulting from fermentation broth processing, i.e. from nanofiltration (retentate) and bipolar electrodialysis (diluate, concentrate) was carried out in three steps with 0.1 mol/L Aliquat 336 or Cyanex 923 as extractants in octanol, at w/o = 1. The concurrent extraction was realized by contacting in each step an aqueous raffinate with fresh organic phase. A solution of 0.2 mol/L NaOH was used as a stripping phase. 2.5. Analytical methods Concentration of fumaric acid was determined by polarography (Metrohm 797 VA Computrance). To determine concentration of chloride anions, the Volhard method was used (Metrohm 702 SM Titrino). Other fermentation components including acetic acid, citric acid, succinic acid, cordycepic acid ([(2R,3R,4R,5R)-hexan1,2,3,4,5,6-hexol] known as mannitol) and glycerol were determined by the reversed-phase high performance liquid chromatography (HPLC) using the Rezex ROA Organic Acid H + (Phenomenex) and 2.5 mM sulfuric acid as a mobile phase _ zyn _ ´ ska et al., 2010). (Staszak et al., 2013; Drozd 3. Calculations The retention of organic acids obtained in nanofiltration process was determined according to the formula:
Cp 100% R¼ 1 Cf
ð1Þ
where Cp, Cf are the concentration of an organic acid in the permeate and in the feed solution, respectively. The average value of the current efficiency was calculated on the basis of the following equation:
CE ¼
F zþ tþ V dil DC dil 100% n I Dt
ð2Þ
where: F is a Faraday‘s constant [C/mol], z+, m+ are ionic valence and number of cations, respectively, Vdil is the volume of diluate [L], DCdil stands for the concentration difference in diluate compartment [mol/L], n is the number of cell pairs, Dt is the time interval [s] and I is the current [A]. The average value of energy consumed for 1 kg of fumaric acid production (E) was determined using the equation:
E¼
UIt ; kWh=kg m
ð3Þ
where: U is the voltage[V] and m stands for the mass of fumaric acid [kg].
The recovery ratio of fumaric acid (gFum) obtained during bipolar electrodialysis was calculated as follows:
gFum ¼ 1
C tdil
!
C 0dil
100%
ð4Þ
where: C 0dil ; C tdil are the initial concentrations and concentrations at the end of the process in diluate chamber [g/L], respectively. The extraction efficiency (percentage extraction, E) was calculated from the contents of the acid in the aqueous phases before (C0) and after (C) extraction:
E¼
C0 C 100% C0
ð5Þ
4. Results and discussion 4.1. Determination of fermentation broth composition by HPLC Prior to separation, the components of fermentation broth were determined chromatographically. The influence of the HPLC mobile phase composition on separation of fermentation broth compounds was checked. Concentration of sulfuric acid was changed between 1.25 and 5 mM, which corresponded to the pH of mobile phase between 2.7 and 2.1. The sulfuric acid concentration in the mobile phase was found to have a slight effect on the retention times of fumaric, succinic, citric, acetic, and cordycepic acids, and no effect on the retention times of other compounds. In all analyses the concentration of sulfuric acid in water was 2.5 mM (pH of the mobile phase was 2.4). Limits of quantification of the broth components varied between 0.01 and 0.04 g/L. The compositions of the fermentation broths applied in the investigation are given in Table 1. 4.2. Nanofiltration of fermentation broths Nanofiltration is a separation technique whose selectivity is governed both by steric hindrance effects and electrostatic repulsion. In general, nanofiltration membranes could retain compounds of molecular weight up to 200 Da and charged molecules, especially multivalent ions. As mentioned above, organic acids can be produced by bioconversion. However, the fermentation process generates an acid salt solution (sodium, ammonium or calcium salt) containing different impurities like the substrate (i.e. glucose, glycerol) or mineral salts. Thus, further operations of purification, concentration and conversion are needed to obtain the acid in a suitable form. Nanofiltration can be considered an appropriate operation of purification before the conversion to acid. Nanofiltration has been proposed to be applied for the separation of lactate (Bouchoux et al., 2006) or succinate (Kang and Chang, 2005) salt from other fermentation broth components. In this work the nanofiltration of fermentation broth II (Table 1) was performed in a laboratory set-up SEPA Osmonics and its results were compared to those of the nanofiltration of fermentation broth I carried out on a pilot scale NF, described in the
Table 1 Composition of the fermentation broths applied in the investigation. Fermentation broth
I II
Concentration (g/L)
pH
Fum
Suc
Ac
Cit
Cor
Gly
[Cl]
2.05 1.99
0.16 0.00
0.18 0.00
0.03 0.14
0.00 1.74
2.46 2.27
0.36 0.00
6.2 6.4
Fum – fumaric acid, Suc – succinic acid, Cit – citric acid, Ace – acetic acid, Cor – cordycepic acid, Gly – glycerol, [Cl] – chloride anions.
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previous work (Staszak et al., 2014). The transmembrane pressure effect on the degree of retention and permeate flux in the nanofiltration process, was taken into account as TMP is a very important factor in the pressure-driven processes, such as nanofiltration. Generally, with increasing TMP, convective transport becomes dominant and imposes increased rejection. However, concentration polarization also increases with increasing transmembrane pressure, which results in decreasing rejection (Luo and Wan, 2013). The results of investigation of transmembrane pressure effect on the degree of retention and value of permeate flux are presented in Table 2 and Fig. 2, respectively. The applied transmembrane pressure had little influence on the retention of fermentation components, while the retention of fumaric acid and glycerol slightly decreased with increasing TMP. A similar relationship has been noted for the separation of succinic and citric acids by nanofiltration process at pressure varied from 0.13 to 0.28 MPa (Kang and Chang, 2005) and for separation of fumaric acid under pressure of 0.4 and 0.8 MPa (Staszak et al., 2014). It is obvious that the use of high TMP brings increased permeate flux, which results in high efficiency, as shown in Fig. 2. Small differences were noted in flux of the permeate obtained upon filtration of water and fermentation broth II in the NF process with the polymeric membrane. This is typically due to the osmotic pressure difference induced by the separation but also to the higher viscosities of the permeating solutions when compared to water. Similar effect during the nanofiltration of fermentation broth was observed by Bouchoux et al. (2006). The permeation fluxes obtained for sodium lactate fermentation broth by Kang et al. (2004) with NF45 membrane and Bouchoux et al. (2006) with DK membrane from GE Osmonic have been reported to reach the following values 0.02 m3/m2 h at TMP = 2.7 MPa and 0.035 m3/m2 h at TMP = 2 MPa, respectively. Some decrease in the permeate flux rate results from the membrane fouling. Feed solution composition (i.e. pH, ionic strength, salt and organic content), temperature, filtration geometry, operating pressure and membrane characterization (i.e. surface roughness, zeta potential, hydrophobicity) can affect the membrane susceptibility to fouling. Thus, fouling layer formation and membrane flux decline strongly depend on the interaction between the particles and membrane surface. Moreover, the results presented in Fig. 2 show that the initial water flux and the flux obtained after cleaning procedure have almost the same value. This indicates that in the processes investigated there is no irreversible fouling. The retentions of broth II components are shown in Table 2. Irrespective of the membrane used, concentration and separation of the organic acids from glycerol by nanofiltration were successful.
Fig. 2. Permeate flux of water and fermentation broth II vs. TMP in the laboratory set-up SEPA Osmonics.
In general, organic acids are weak and undergo dissociation at high pH. As the retention of weak acids and bases is highly dependent on pH, their retention in the NF process should be greater in the ionized form. The pH of the fermentation broths was about 6, thus above pK of the acids studied. The rejections of citric acid (MW = 192 Da) and cordycepic acid (MW = 182 Da), whose MW is close to cut-off of the membrane, were very high (100%) irrespective of the type of fermentation broth and membrane. It can be assumed that the high retention of these acids obtained during nanofiltration of the fermentation broths results from the size and geometry of the separated particles. A similar relationship has been observed by other authors (Choi et al., 2008) in their studies on the removal of organic acids from wastewaters using nanofiltration membranes. For ES10 membrane (cut-off 100 Da), the rejections of succinic acid (MW = 118 Da) and citric acid, whose MW are higher than or close to the cut-off of the membrane, were very high (over 90%) irrespective of pH. This means that a reduced surface charge of the NF membrane and neutral form of the organic acids below pKa appear to limit the amount of electrostatic repulsion between the membrane and organic solute, and the sieving effect related to the molecular size of the compounds appears to have an important role. Also Van der Bruggen et al. (1999) have reported that the rejection of negatively charged organic solutes with a molecular size close to the pore size of the NF membrane was driven more by sieving than by electrostatic repulsion. The retention degree of succinic acid (118 Da) and citric acid are higher than that of fumaric acid one, while the retention degree of acetic acid (60 Da) is the smallest of all studied organic acids. For the ceramic membrane, the rejection of acetic acid is 69%, implying that the separation mechanism of this acid by the NF membrane
Table 2 Retention and composition of retentate of fermentation components during NF process. Fermentation broth
I II
Concentration (g/L) I II
Retention (%) MPa
Fum
Suc
Cit
Ac
Cor
Gly
[Cl]
1.4* 0.8 1.2 1.4
79.0 95.2 94.3 92.3
100.0 – – –
99.0 100.0 100.0 100.0
68.9 – – –
– 100.0 100.0 100.0
5.7 12.8 11.4 11.5
42.4 – – –
1.4* 0.8 1.2 1.4
2.38 2.78 2.95 3.71
0.17 – – –
0.04 0.19 0.19 0.28
0.21 – – –
– 2.67 2.55 3.23
Fum – fumaric acid, Suc – succinic acid, Cit – citric acid, Ac – acetic acid, Cor – cordycepic acid, Gly – glycerol, [Cl] – chloride anions. * Results from Staszak et al. (2014).
0.08 0.62 0.67 0.43
0.29 – – –
K. Prochaska et al. / Bioresource Technology 167 (2014) 219–225
may involve only electrostatic repulsion due to molecular size much smaller than the cut-off of the NF membrane. The observed retention of the uncharged component – glycerol – is very low (below 13%). This result can be explained by the absence of steric hindrance effects and electrostatic interactions. A similar observation has been described in literature (Van der Bruggen et al., 2006). Moreover, it has been shown that the presence of mineral salts causes a decrease in the process selectivity. The results obtained indicate that nanofiltration could be applied as one of the purification and concentration steps for the separation of fermentation components.
4.3. Bipolar electrodialysis of fermentation broths In the second step, the bipolar electrodialysis of fermentation broth after nanofiltration pre-treatment was investigated. The process was performed under a constant electric field at 120 A/m2 of current density for 2.5 h. Fig. 3 illustrates the changes in concentration of the fermentation components in diluate chamber, between the beginning of the EDBM process (t = 0 h) and at its end (t = 2.5 h). The concentrations of fumaric acid and succinic acid in diluate compartment were changed during bipolar electrodialysis of fermentation broth I, while the concentrations of other components remained constant. This selective separation of dicarboxylic acids was achieved by the anion-exchange membrane (PC 200D) and the stack configuration applied. The effect of cell configurations on the performance of organic acids production by EDBM process has been described by other authors (Huang et al., 2007). It should be noted that only BP-AM stack configuration makes it possible to investigate the competition between the acidic anions. The transport of citric acid and acetic acid through the anionexchange membrane is limited due to the geometries and the structures of these compounds, which differ significantly from the geometry and structure of dicarboxylic acid. Wang et al. (2011) have indicated that the type of acid species and the transport number of acid anions in the anion-exchange membrane were responsible for the permselectivity differences. Furthermore, a small amount of chloride anions was found to be able to pass through the membrane due to the anion small size and high mobility. The chloride transport could be also explained by incomplete exclusion of small ions, because ion-exchange membranes are not perfectly selective (Wilhelm et al., 2001). The results obtained in EDBM process of broth I are compared with those obtained in bipolar electrodialysis of broth II.
Fig. 3. Changes in concentration of fermentation components in the diluate chamber vs. time of bipolar electrodialysis.
223
On the basis of the results obtained, the current efficiency (CE), the energy consumed for 1 kg of fumaric acid produced (E) and the recovery ratio of fumaric acid (gFUM) were calculated. CE is equal to 0.74% and 0.67%, E 7.9 and 7.3 kWh/kg, gFUM 41.4% and 38.5% for fermentation broth I and II, respectively. The lowest value of fumaric acid recovery ratio (38.5%) was obtained in bipolar electrodialysis of fermentation broth II. The transport of fumarate anions can be limited by the competitive diffusion of cordycepic anions. It should be also pointed out that this competitive diffusion considerably decreases the current efficiency (Tongwen and Weihua, 2002). In the experiments, pH-values were changed from 6.2 to 12.4 (Fig. 4). Taking into account the dissociation constants of fumaric (pKa1 = 3.02, pKa2 = 4.38) and cordycepic acids (pKa = 11.5), the transport of fumarate anions is possible beginning from pH above 6, but when pH of the diluate solution reaches 11, cordycepic anions can also permeate across the membrane. The energy consumed for 1 kg of fumaric acid produced was higher for bipolar electrodialysis of broth I. The energy consumption is significantly affected by the cell voltage and by the amount of produced fumaric acid, as shown in Eq. (3). However, the differences in energy consumption can be also related to the different compositions of the broths. The presence of additional charge carriers like chloride, citrate ions, etc., could be responsible for reduction of overall resistance (Fig. 4). However, the voltage drop for both fermentation broths during bipolar electrodialysis process is similar, owing to minor differences in the value of the broth ionic strength (lbroth_I = 0.069, lbroth_II = 0.047). To sum up, bipolar electrodialysis can be used as the second step of selective separation and concentration of fumaric acid from the broth. As a result of bipolar electrodialysis of fermentation broth, a 61% recovery of fumaric acid was obtained. It should be noted that in the EDBM process, fumaric acid can be concentrated and isolated from the other components like acetic acid, citric acid, mineral salts as well as unreacted glycerol. It is also found that the composition of the broth has a significant influence on the recovery ratio and energy consumed in the process. 4.4. Reactive extraction of fermentation broths The most important features that determine the attractiveness of the liquid–liquid extraction as a separation technique are as follows: a wide range of technical and technological solutions, the possibility of solute separation from low concentrated or unconventional solutions, high purity of products, solute recovery
Fig. 4. The overall voltage drop and changes in pH-value in the diluate chamber vs. time of bipolar electrodialysis of the fermentation broths studied.
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from waste streams, secondary sources and the possibility of byproduct recovery (Kurzrock and Weuster-Botz, 2010; Rydberg et al., 2004). These advantages have prompted the choice of the extraction method for fumaric acid recovery. As follows from literature, the reactive extraction with organophosphorus extractants, aliphatic amines or quaternary ammonium salts has been successfully applied for separation of a vast variety of carboxylic acids (Kertes and King, 2009; Labbaci et al., 2010; Wis´niewski and Pierzchalska, 2005; Yang et al., 2013), i.e. lactic, propionic, succinic, maleic, oxalic, acetic, etc. Prior to the three-step extraction of fumaric acid from the solutions left after the fermentation broth processing, some solvating (TBP and Cyanex 923) or basic (TOA and Aliquat 336) extractants were screened for fumaric acid removal from the feed at various initial pH values. Aliquat 336 (basic extractant) and Cyanex 923 (solvating extractant) were selected from the extractants studied (Table 3) as the most effective for fumaric acid removal. Although TBP seems to extract fumaric acid similarly to Cyanex 923, it was not chosen for further investigation because of its relatively high solubility in water (280 mg/L at 25 °C) and tendency to hydrolyze (Kertes and Halpern, 1961). As Aliquat 336 extracts from 40% to 70% fumaric acid at pH range from 2 to 9, it means that both forms, i.e. fumaric acid and fumarate, can be extracted efficiently with this quaternary ammonium salt. Such an efficient extraction can be attributed to the following reactions of the acid (H2Fum) with the extractant (R4N+Cl) (Kyuchoukov and Yankov, 2005):
2ðR4 Nþ Cl Þorg þ H2 Fumaq $ ð2½R4 Nþ Cl : H2 FumÞorg
ð6Þ
þ 2 2ðR4 Nþ Cl Þorg þ Fum2 aq $ ð½R4 N 2 Fum Þorg þ 2Claq
ð7Þ
Kyuchoukov and Yankov (2005) have indicated that the concentration ratio between the extracted undissociated molecules and dissociated anions depended not only on pH but also on the total concentration of the acid in the aqueous phase. Although, their studies concerned the extraction from aqueous solutions with a high content of chlorides, it seems that also for the solutions studied in this work (chloride concentration 0.1 mol/L) the molar ratio of the complex made by fumaric acid:Aliquat 336 in the organic phase is close to 1:2. As 0.05 mol/L fumaric acid contains twice as much carboxylic groups, thus 0.1 mol/L extractant should extract as maximum 50% of the fumaric acid. In fact, the percentage extraction reaches 70% and probably results from formation of the other ion pairs according to the reaction (Matsumoto et al., 1999):
HFumaq þ ðR4 Nþ Cl Þorg ! ðR4 Nþ HFum Þorg þ Claq
H2 Fumaq þ 2Cyanex923org $ ðH2 Fum 2Cyanex923Þorg
ð9Þ
Thus, with increasing pH, i.e. with decreasing content of the acidic form, the extraction of fumaric acid decreases. The acid was stripped with 0.2 mol/L NaOH from the organic phase loaded at pH 2 and 6, and the efficiency of stripping exceeded 80%. Sodium fumarate formed as a result of stripping can be easily converted into fumaric acid, if necessary. The diluate and concentrate after preliminary treatment, i.e. bipolar electrodialysis process (Fig. 1), were extracted in three steps with solutions of Aliquat 336 or Cyanex 923 in octanol. Percentage extraction of fumaric acid after one, two and three extraction steps and changes in pH of the aqueous phases are shown in Table 4. Percentage extraction of fumaric acid from real solutions both with solvating (Cyanex 923) and basic (Aliquat 336) extractants is high and after three steps exceeds 85% and 70%, respectively. The three-step extraction of fumaric acid proves that the acid can be efficiently removed both from the diluate and the concentrate after bipolar electrolysis. It has been shown that the extraction efficiency with Cyanex 923 from the real solutions differs from that from the model solutions shown in Table 3. Although, the diluate pH before extraction exceeds 12 (Table 4), the percentage extraction of fumaric acid even after one step of extraction reaches 70%. Compared with the model solution of pH 9 and only 20% extraction of the acid, it is obvious that the presence of other species in the real solution enhances the fumarate extraction. The efficiency of the three-step extraction with both extractants from the concentrate yields almost 100%. It is enhanced by acidic pH definitely lower in the concentrate (initially equal to even 2.3) than in the diluate (initial pH above 12). After each step of extraction, the pH of the concentrate increases from the initial pH 2.3 to 7.4 as a result of fumaric acid Table 4 Changes in extraction efficiency and pH after 1, 2 and 3 stage of fumaric acid extraction with 0.1 mol/L Cyanex 923 or Aliquat 336 in octanol from the diluate and the concentrate obtained in bipolar electrodialysis. Diluate
E1 E1+2 E1+2+3 pH0 pH1 pH2 pH3
Concentrate
Cyanex 923
Aliquat 336
Cyanex 923
Aliquat 336
72 79 86 12.8 12.3 12.3 11.9
30 52 71 12.8 11.6 11.5 11.4
62 90 98 2.3 5.6 6.8 7.3
71 91 97 2.3 6.7 7.0 7.1
ð8Þ
or partial participation of octanol in the extraction (Tamada and King, 1990). On the other hand, solvating extractants, e.g. Cyanex 923, transport the acid to the organic phase as a result of the acid molecule solvation (Starr and King, 1992):
Table 3 Dependence of the extraction efficiency of fumaric acid on the initial pH of the model feed solution (C0 = 1.2 g/L, i.e. 0.1 mol/L) for various organic solutions of 0.1 mol/L extractants in octanol. Type of extractant
Aliquat 336 TOA TOA + TBP TBP Cyanex 923
EFum (%) pH 2
pH 6
pH 9
61 13 13 72 71
45 6 17 18 35
57 7 5 45 15
Fig. 5. Three step extraction efficiency of fumaric acid with 0.1 mol/L Aliquat 336 in octanol from the retentate obtained in NF process.
K. Prochaska et al. / Bioresource Technology 167 (2014) 219–225
concentration decrease in the aqueous phase (Table 4). On the other hand, pH of the diluate after extraction does not change significantly and is still basic near 12, which means that fumaric acid is extracted from the diluate as a fumarate. Fumaric acid extraction from nanofiltration retentate is not as effective as from electrodialysis diluate and concentrate (Fig. 5). Initial pH of the retentate before extraction is 6.5 and does not change significantly after the three-step extraction. At this pH identification of a single extraction mechanism is hardly possible because of the presence of various forms of fumaric acid in the aqueous solution that affects the extraction efficiency. However, it is clear that in all cases the three-step extraction and stripping can support membrane techniques to separate dicarboxylic acid from the fermentation broth. 5. Conclusion A novel approach based on a hybrid system permitting the performance of nanofiltration, bipolar electrodialysis and reactive extraction is proposed for the recovery of fumaric acid from the fermentation broths resulting from bioconversion of glycerol. This hybrid system enables fumaric salt to be concentrated even up to 95% (depending on TMP), to be further converted to fumaric acid with AM BM stack in EDBM process. Finally, fumaric acid can be removed in a three-step reactive extraction with commercial extractants even at 90% efficiency. Extraction and stripping can support membrane techniques to separate efficiently dicarboxylic acid from the fermentation broth. Acknowledgements This research was financially supported within the project ‘‘Biotechnological conversion of glycerol to polyols and dicarboxylic acids,’’ implemented within the Operational ProgrammeInnovative Economy, 2007–2013, co-financed by the European Union. PO IG 01.01.02.074/09. References Bouchoux, A., Roux-de Balmann, H., Lutin, F., 2006. Investigation of nanofiltration as a purification step for lactic acid production processes based on conventional and bipolar electrodialysis operations. Sep. Purif. Technol. 52, 266–273. Choi, J.-H., Fukushi, K., Yamamoto, K., 2008. A study on the removal of organic acids from wastewaters using nanofiltration membranes. Sep. Purif. Technol. 59, 17– 25. Da Silva, A.H., Miranda, E.A., 2013. Adsorption/desorption of organic acids onto different adsorbents for their recovery from fermentation broths. J. Chem. Eng. Data 58, 1454–1463. Deng, Y., Li, Y., Xu, Q., Gao, M., Huang, H., 2012. Production of fumaric acid by simultaneous saccharification and fermentation of starchy materials with 2deoxyglucose-resistant mutant strains of Rhizopus oryzae. Bioresour. Technol. 107, 363–367. _ _ ´ ska, A., Czaczyk, K., Pawlicka, J., 2010. The use of high performance liquid Drozdzyn chromatography (HPLC) for determination of polyols in fermentation broth. Aparatura Badawcza i Dydaktyczna 4, 121–128. Huang, C., Xu, T., Zhang, Y., Xue, Y., Chen, G., 2007. Application of electrodialysis to the production of organic acids: state-of-the-art and recent developments. J. Membr. Sci. 288, 1–12. Kang, S.H., Chang, Y.K., 2005. Removal of organic acid salts from simulated fermentation broth containing succinate by nanofiltration. J. Membr. Sci. 246, 49–57. Kang, S.H., Chang, Y.K., Chang, H.N., 2004. Recovery of ammonium lactate and removal of hardness from fermentation broth by nanofiltration. Biotechnol. Prog. 20, 764–770.
225
Kertes, A.S., Halpern, M., 1961. Hydrochloric acid promoted hydrolysis of tri-n-butyl phosphate. J. Inorg. Nucl. Chem. 20, 117–126. Kertes, A.S., King, J., 2009. Extraction chemistry of fermentation product carboxylic acids. Biotechnol. Bioeng. 103, 432–444. Kordowska-Wiater, M., Polak-Berecka, M., Was´ko, A., Targon´ski, Z., 2012. Protoplast fusion of Rhizopus oryzae and Rhizopus microsporus for enhanced fumaric acid production from glycerol. J. Biotechnol. Comput. Biol. Bionanotechnol. 93, 425– 430. Kurzrock, T., Weuster-Botz, D., 2010. Recovery of succinic acid from fermentation broth. Biotechnol. Lett. 32, 331–339. Kyuchoukov, G., Yankov, D., 2005. Mechanism of lactic acid extraction with quaternary ammonium chloride (Aliquat 336). Ind. Eng. Chem. Res. 44, 5733– 5739. Labbaci, A., Kyuchoukov, G., Albet, J.L., Molinier, J., 2010. Detailed investigation of lactic acid extraction with tributylphosphate dissolved in dodecane. J. Chem. Eng. Data 55, 228–233. Luo, J., Wan, Y., 2013. Effects of pH and salt on nanofiltration – a critical review. J. Membr. Sci. 438, 18–28. Matsumoto, M., Takagi, T., Nakaso, T., 1999. Extraction equilibria of organic acids with tri-n-octylmethylammonium chloride. Solvent Extr. Res. Dev. Jpn. 6, 144– 150. Nakajima-Kambe, T., Nozue, T., Mukouyama, M., Nakahara, T., 1997. Bioconversion of maleic to fumaric acid by pseudomonas alcaligenes Strain XD-1. J. Ferment. Bioeng. 84, 165–168. Rydberg, I., Cox, M., Musicas, C., Choppin, G.R., 2004. Solvent Extraction and Practice. Taylor & Francis, New York. Song, C.W., Kim, D.I., Choi, S., Jang, J.W., Lee, S.Y., 2013. Metabolic engineering of Escherichia coli for the production of fumaric acid. Biotechnol. Bioeng. 110, 2025–2034. Starr, N.J., King, C.J., 1992. Water-enhanced solubility of carboxylic acids in organic solvents and its application to extraction processes. Ind. Eng. Chem. Res. 31, 2572–2579. Staszak, K., Woz´niak, M.J., Karas´, Z., Staniewski, J., Prochaska, K., 2013. Application of nanofiltration in the process of the separation of model fermentation broths components. Pol. J. Chem. Technol. 15, 1–4. Staszak, K., Woz´niak, M., Sottek, M., Karas´, Z., Prochaska, K., 2014. Removal of fumaric acid from simulated and real fermentation broth. J. Chem. Technol. Biotechnol. http://dx.doi.org/10.1002/jctb.4311. Tamada, J.A., King, C.J., 1990. Extraction of carboxylic acids with amine extractants. 2. Chemical interactions and interpretation of data. Ind. Eng. Chem. Res. 29, 1327–1333. Tongwen, X., Weihua, Y., 2002. Effect of cell configurations of the performance of citric acid production by a bipolar membrane electrodialysis. J. Membr. Sci. 203, 145–153. Van der Bruggen, B., Schaep, J., Wilms, D., Vandecasteele, C., 1999. Influence of molecular size, polarity and change on the retention of organic molecules by nanofiltration. J. Membr. Sci. 156, 29–41. Van der Bruggen, B., Verliefde, A., Braeken, L., Cornelissen, E.R., Moons, K., Verberk, J.Q.J.C., van Dijk, H.J.C., Amy, G., 2006. Assessment of a semi-quantitative method for estimation of the rejection of organic compounds in aqueous solution in nanofiltration. J. Chem. Technol. Biotechnol. 81, 1166–1176. Wang, Y., Zhang, N., Huang, C., Xu, T., 2011. Production of monoprotic, diprotic, and triprotic organic acids by using electrodialysis with bipolar membranes: effect of cell configurations. J. Membr. Sci. 385–386, 226–233. Wilhelm, F.G., Punt, I., Van der Vegt, N.F.A., Wessling, M., Strathmann, H., 2001. Optimisation strategies for the preparation of bipolar membranes with reduced salt ion leakage in acid–base electrodialysis. J. Membr. Sci. 182, 13–28. Wis´niewski, M., Pierzchalska, M., 2005. Recovery of carboxylic acids C1–C3 with organophosphine oxide solvating extractants. J. Chem. Technol. Biotechnol. 80, 1425–1430. Xu, Q., Li, S., Fu, Y., Tai, C., Huang, H., 2010. Two-stage utilization of corn straw by Rhizopus oryzae for fumaric acid production. Bioresour. Technol. 101, 6262– 6264. Yang, G., Sarwar Jahan, M., Ahsan, L., Zheng, L., Ni, Y., 2013. Recovery of acetic acid from pre-hydrolysis liquor of hardwood kraft-based dissolving pulp production process by reactive extraction with triisooctylamine. Bioresour. Technol. 138, 253–258. Zhang, J., Tang, L., Zhang, H., Yang, Y., Mao, Z., 2012. A novel and cleaner technological process of extracting L-glutamic acid from fermentation broth by two-stage crystallization. J. Cleaner Prod. 20, 137–144. Zhao, W., Sun, X., Wang, Q., Ma, H., Teng, Y., 2009. Lactic acid recovery from fermentation broth of kitchen garbage by esterification and hydrolysis method. Biomass Bioenergy 33, 21–25.
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Nanofiltration, bipolar electrodialysis and reactive extraction hybrid system for separation of fumaric acid from fermentation broth Krystyna Prochaska ⇑, Katarzyna Staszak, Marta Joanna Woz´niak-Budych, Magdalena Regel-Rosocka, Michalina Adamczak, Maciej Wis´niewski, Jacek Staniewski ´ , Poland Poznan University of Technology, Institute of Chemical Technology and Engineering, pl. M. Skłodowskiej-Curie 2, 60-965 Poznan
h i g h l i g h t s Hybrid system for fumaric acid recovery from fermentation broth is proposed. The system involves nanofiltration, bipolar electrodialysis and reactive extraction. Fumaric salts can be efficiently concentrated in nanofiltration process. Bipolar electrodialysis allows selective separation of fumaric acid. Three-step extraction of fumaric acid with Aliquat 336 and Cyanex 923 is efficient.
a r t i c l e
i n f o
Article history: Received 17 April 2014 Received in revised form 2 June 2014 Accepted 4 June 2014 Available online 11 June 2014 Keywords: Nanofiltration Reactive extraction Bipolar electrodialysis Fumaric acid Fermentation broth
a b s t r a c t A novel approach based on a hybrid system allowing nanofiltration, bipolar electrodialysis and reactive extraction, was proposed to remove fumaric acid from fermentation broth left after bioconversion of glycerol. The fumaric salts can be concentrated in the nanofiltration process to a high yield (80–95% depending on pressure), fumaric acid can be selectively separated from other fermentation components, as well as sodium fumarate can be conversed into the acid form in bipolar electrodialysis process (stack consists of bipolar and anion-exchange membranes). Reactive extraction with quaternary ammonium chloride (Aliquat 336) or alkylphosphine oxides (Cyanex 923) solutions (yield between 60% and 98%) was applied as the final step for fumaric acid recovery from aqueous streams after the membrane techniques. The hybrid system permitting nanofiltration, bipolar electrodialysis and reactive extraction was found effective for recovery of fumaric acid from the fermentation broth. Ó 2014 Elsevier Ltd. All rights reserved.
1. Introduction Organic acids are mainly produced by microbial fermentation (Deng et al., 2012) resulting in generation of fermentation broth containing organic salts and some impurities like sugars and mineral salts. In fact, many operations are necessary to separate and purify the final product (organic acid) from the fermentation broth. For example fumaric acid can be produced by fermentation in the presence of Escherichia coli species (Song et al., 2013). It was found that under aerobic conditions E. coli were able to produce 28 g/L of fumaric acid, however, during bacterial fermentation a substantial amount of acetic acid was formed. Nakajima-Kambe et al. (1997) tested the influence of temperature, pH and type of carbon sources ⇑ Corresponding author. Tel.: +48 61 665 3601; fax: +48 61 665 3649. E-mail address: [email protected] (K. Prochaska). http://dx.doi.org/10.1016/j.biortech.2014.06.010 0960-8524/Ó 2014 Elsevier Ltd. All rights reserved.
(such as maleic, malonic, itaconic, adicipic and succinic acids) on the rate of the bioconversion. The highest fumaric acid productivity was obtained in the temperature range between 30 and 45 °C, at pH 7 and with maleic acid used as a carbon source. Under these conditions, above 40 g/L of fumaric acid and almost threefold less of L-malic acid, as a by-product, were obtained after 6 h of incubation. Xu et al. (2010) have reported that fumaric acid could be produced from two-stage utilization of corn straw in the presence of Rhizopus oryzae strain. The xylose-rich hydrolysates obtained as a result of acid hydrolysis of corn straw, were responsible for the growth of microorganisms. The corn straw left after acid hydrolysis was used in the next step for fumaric acid production in glucoserich hydrolysates upon enzymatic hydrolysis. Under the optimal conditions the fumaric acid production reached up to 28 g/L. The protoplast fusion of R. oryzae and Rhizopus microsporus strains for fumaric acid production from glycerol was proposed by
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Kordowska-Wiater et al. (2012). It was shown that double fusion led to an increase in fumaric acid productivity in relation to the parental strains. Fermentation of glycerol as the only carbon source in the medium, resulted in formation of small amounts of lactic acid and around 30 g/L of fumaric acid. These reports imply that many additional operations are necessary to separate and purify the major product (an organic acid) from the broth. Da Silva and Miranda (2013) have suggested the application of adsorption/ desorption on activated carbon and a weak base resin for the recovery of an organic acid from the broth. Zhang et al. (2012) have proposed a two-stage crystallization to extract glutamic acid from fermentation broth. By means of the proposed technique, glutamic acid was recovered in 83% in the first stage including isoelectric crystallization, while more than 70% of the remaining glutamic acid was separated in the second stage by evaporative crystallization. One of the techniques commonly used to purify organic acids from the broth is esterification. In other reports, Zhao et al. (2009) have presented the possibilities of lactic acid recovery from fermentation broth of kitchen garbage by esterification and hydrolysis. The process was carried out in two steps: first, lactate ester was produced by esterification of ammonium lactate of 96% yield, and then the lactate ester was purified and hydrolyzed to lactic acid in the presence of a cation-exchange resin. In this investigation, a hybrid system consisting of three stages of nanofiltration (NF), bipolar electrodialysis (EDBM) and reactive extraction was proposed for separation of fumaric acid from the fermentation broth left after bioconversion of glycerol (Fig. 1). At first, nanofiltration was performed as a pre-treatment step to concentrate organic acids and separate glycerol from the other components of the broth. Two types of devices were used at the nanofiltration stage: a laboratory setup equipped with a flat sheet polymeric membrane, and a pilot scale NF system equipped with a tubular ceramic membrane (Staszak et al., 2014). At the second stage, bipolar electrodialysis of the nanofiltration retentate, containing concentrated organic acids, was carried out, and after that reactive extraction of the nanofiltration retentate and diluate after bipolar electrodialysis were used to recover the residues of fumaric acid. 2. Methods 2.1. Materials Two fermentation broths of different compositions coming from biotechnological conversion of glycerol were investigated. The research material was delivered by one of the collaborators in the frames of the project: ‘‘Biotechnological conversion of glycerol to polyols and dicarboxylic acids.’’ The method of fermentation is protected by the copyright (Kordowska-Wiater et al., 2012).
Various solvating (tributyl phosphate – TBP, mixture of trialkylphosphine oxides – Cyanex 923) or basic (trioctylamine – TOA, methyltrioctylammonium chloride – Aliquat 336) extractants were used as received to prepare 0.1 mol/L organic solutions of extractant in octanol. 2.2. Nanofiltration experiments A laboratory setup SEPA Osmonics (GE Osmonics, USA) with polymeric flat sheet membrane (Koch Membrane System, UK) was used. The properties of the membrane used in this study are: cut off 200 Da, effective surface area 0.0155 m2, pH range: 0–14. Hydrodynamic coefficient was experimentally measured using demineralized water at 25 °C and was equal to 0.021 L/m2 h MPa. All processes of nanofiltration were performed at 25 ± 1 °C and transmembrane pressure (TMP) in the 0.8–1.4 MPa range. Prior to all the experiments, the initial flux of water at a specified transmembrane pressure was tested. After each experiment, the nanofiltration modules were cleaned with water until the initial water flux was recovered. During nanofiltration 3 L of solution from the feed vessel was pumped to the membrane module, and the retentate was circulated in a closed loop with a volume flow of 160 L/h (0.7 m/s). Experiments were performed for no longer than 2 h. Moreover, the results of nanofiltration experiments were compared with those described in the previous work (Staszak et al., 2014) in which the pilot scale nanofiltration module with monochannel tubular ceramic membrane was used. 2.3. Bipolar electrodialysis experiments Three-chamber laboratory ED setup with a stack consisting of bipolar (PC 200bip) and anion-exchange (PC 200D) membranes produced by PCCell GmbH separated by 10 mm polycarbonate spacers, was used in this study. The effective surface area of membrane stack was equal to 0.0064 m2. The electrodialysis stack was connected with a peristaltic pump (Verder), DC power supply (NDN) and a multifunction meter (Elmetron) measuring the pH, the conductivity and the temperature of working solutions. The anode was made of titanium plated with iridium and the cathode was made of steel 314. Bipolar electrodialysis process was performed at 25 ± 1 °C under constant electric field conditions at 120 A/m2 of current density. Experiments were conducted until a constant value of conductivity was obtained. The working solution containing fumaric salts was fed to the diluate chamber and the solution with fumaric acid instead of water (to reduce the overall resistance) was introduced to the concentrate chamber. In the electrode chambers, sodium sulfate
Fig. 1. Hybrid system for separation of fumaric acid from fermentation broth.
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solution was placed to ensure current transport during the process. The applied constant electric field initiated the transport of fumarate anions through the anion-exchange membrane to the concentrate chamber and in the same time the formation of H+ and OH ions in the transition region of bipolar membrane. In fact, fumaric anions and hydrogen ions enter the concentrate chamber forming fumaric acid. The stack configuration used in this investigation can be applied to convert organic salts into organic acids. 2.4. Reactive extraction experiments Reactive extraction of the solutions studied was carried out in a typical way: the aqueous feed was mechanically shaken with the same volume of the organic phase for 30 min at 25 °C in glass separatory funnels, and then allowed to stand for phase separation. The influence of pH on fumaric acid extraction with various solvating extractant solutions was investigated. Reactive extraction of the solutions resulting from fermentation broth processing, i.e. from nanofiltration (retentate) and bipolar electrodialysis (diluate, concentrate) was carried out in three steps with 0.1 mol/L Aliquat 336 or Cyanex 923 as extractants in octanol, at w/o = 1. The concurrent extraction was realized by contacting in each step an aqueous raffinate with fresh organic phase. A solution of 0.2 mol/L NaOH was used as a stripping phase. 2.5. Analytical methods Concentration of fumaric acid was determined by polarography (Metrohm 797 VA Computrance). To determine concentration of chloride anions, the Volhard method was used (Metrohm 702 SM Titrino). Other fermentation components including acetic acid, citric acid, succinic acid, cordycepic acid ([(2R,3R,4R,5R)-hexan1,2,3,4,5,6-hexol] known as mannitol) and glycerol were determined by the reversed-phase high performance liquid chromatography (HPLC) using the Rezex ROA Organic Acid H + (Phenomenex) and 2.5 mM sulfuric acid as a mobile phase _ zyn _ ´ ska et al., 2010). (Staszak et al., 2013; Drozd 3. Calculations The retention of organic acids obtained in nanofiltration process was determined according to the formula:
Cp 100% R¼ 1 Cf
ð1Þ
where Cp, Cf are the concentration of an organic acid in the permeate and in the feed solution, respectively. The average value of the current efficiency was calculated on the basis of the following equation:
CE ¼
F zþ tþ V dil DC dil 100% n I Dt
ð2Þ
where: F is a Faraday‘s constant [C/mol], z+, m+ are ionic valence and number of cations, respectively, Vdil is the volume of diluate [L], DCdil stands for the concentration difference in diluate compartment [mol/L], n is the number of cell pairs, Dt is the time interval [s] and I is the current [A]. The average value of energy consumed for 1 kg of fumaric acid production (E) was determined using the equation:
E¼
UIt ; kWh=kg m
ð3Þ
where: U is the voltage[V] and m stands for the mass of fumaric acid [kg].
The recovery ratio of fumaric acid (gFum) obtained during bipolar electrodialysis was calculated as follows:
gFum ¼ 1
C tdil
!
C 0dil
100%
ð4Þ
where: C 0dil ; C tdil are the initial concentrations and concentrations at the end of the process in diluate chamber [g/L], respectively. The extraction efficiency (percentage extraction, E) was calculated from the contents of the acid in the aqueous phases before (C0) and after (C) extraction:
E¼
C0 C 100% C0
ð5Þ
4. Results and discussion 4.1. Determination of fermentation broth composition by HPLC Prior to separation, the components of fermentation broth were determined chromatographically. The influence of the HPLC mobile phase composition on separation of fermentation broth compounds was checked. Concentration of sulfuric acid was changed between 1.25 and 5 mM, which corresponded to the pH of mobile phase between 2.7 and 2.1. The sulfuric acid concentration in the mobile phase was found to have a slight effect on the retention times of fumaric, succinic, citric, acetic, and cordycepic acids, and no effect on the retention times of other compounds. In all analyses the concentration of sulfuric acid in water was 2.5 mM (pH of the mobile phase was 2.4). Limits of quantification of the broth components varied between 0.01 and 0.04 g/L. The compositions of the fermentation broths applied in the investigation are given in Table 1. 4.2. Nanofiltration of fermentation broths Nanofiltration is a separation technique whose selectivity is governed both by steric hindrance effects and electrostatic repulsion. In general, nanofiltration membranes could retain compounds of molecular weight up to 200 Da and charged molecules, especially multivalent ions. As mentioned above, organic acids can be produced by bioconversion. However, the fermentation process generates an acid salt solution (sodium, ammonium or calcium salt) containing different impurities like the substrate (i.e. glucose, glycerol) or mineral salts. Thus, further operations of purification, concentration and conversion are needed to obtain the acid in a suitable form. Nanofiltration can be considered an appropriate operation of purification before the conversion to acid. Nanofiltration has been proposed to be applied for the separation of lactate (Bouchoux et al., 2006) or succinate (Kang and Chang, 2005) salt from other fermentation broth components. In this work the nanofiltration of fermentation broth II (Table 1) was performed in a laboratory set-up SEPA Osmonics and its results were compared to those of the nanofiltration of fermentation broth I carried out on a pilot scale NF, described in the
Table 1 Composition of the fermentation broths applied in the investigation. Fermentation broth
I II
Concentration (g/L)
pH
Fum
Suc
Ac
Cit
Cor
Gly
[Cl]
2.05 1.99
0.16 0.00
0.18 0.00
0.03 0.14
0.00 1.74
2.46 2.27
0.36 0.00
6.2 6.4
Fum – fumaric acid, Suc – succinic acid, Cit – citric acid, Ace – acetic acid, Cor – cordycepic acid, Gly – glycerol, [Cl] – chloride anions.
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previous work (Staszak et al., 2014). The transmembrane pressure effect on the degree of retention and permeate flux in the nanofiltration process, was taken into account as TMP is a very important factor in the pressure-driven processes, such as nanofiltration. Generally, with increasing TMP, convective transport becomes dominant and imposes increased rejection. However, concentration polarization also increases with increasing transmembrane pressure, which results in decreasing rejection (Luo and Wan, 2013). The results of investigation of transmembrane pressure effect on the degree of retention and value of permeate flux are presented in Table 2 and Fig. 2, respectively. The applied transmembrane pressure had little influence on the retention of fermentation components, while the retention of fumaric acid and glycerol slightly decreased with increasing TMP. A similar relationship has been noted for the separation of succinic and citric acids by nanofiltration process at pressure varied from 0.13 to 0.28 MPa (Kang and Chang, 2005) and for separation of fumaric acid under pressure of 0.4 and 0.8 MPa (Staszak et al., 2014). It is obvious that the use of high TMP brings increased permeate flux, which results in high efficiency, as shown in Fig. 2. Small differences were noted in flux of the permeate obtained upon filtration of water and fermentation broth II in the NF process with the polymeric membrane. This is typically due to the osmotic pressure difference induced by the separation but also to the higher viscosities of the permeating solutions when compared to water. Similar effect during the nanofiltration of fermentation broth was observed by Bouchoux et al. (2006). The permeation fluxes obtained for sodium lactate fermentation broth by Kang et al. (2004) with NF45 membrane and Bouchoux et al. (2006) with DK membrane from GE Osmonic have been reported to reach the following values 0.02 m3/m2 h at TMP = 2.7 MPa and 0.035 m3/m2 h at TMP = 2 MPa, respectively. Some decrease in the permeate flux rate results from the membrane fouling. Feed solution composition (i.e. pH, ionic strength, salt and organic content), temperature, filtration geometry, operating pressure and membrane characterization (i.e. surface roughness, zeta potential, hydrophobicity) can affect the membrane susceptibility to fouling. Thus, fouling layer formation and membrane flux decline strongly depend on the interaction between the particles and membrane surface. Moreover, the results presented in Fig. 2 show that the initial water flux and the flux obtained after cleaning procedure have almost the same value. This indicates that in the processes investigated there is no irreversible fouling. The retentions of broth II components are shown in Table 2. Irrespective of the membrane used, concentration and separation of the organic acids from glycerol by nanofiltration were successful.
Fig. 2. Permeate flux of water and fermentation broth II vs. TMP in the laboratory set-up SEPA Osmonics.
In general, organic acids are weak and undergo dissociation at high pH. As the retention of weak acids and bases is highly dependent on pH, their retention in the NF process should be greater in the ionized form. The pH of the fermentation broths was about 6, thus above pK of the acids studied. The rejections of citric acid (MW = 192 Da) and cordycepic acid (MW = 182 Da), whose MW is close to cut-off of the membrane, were very high (100%) irrespective of the type of fermentation broth and membrane. It can be assumed that the high retention of these acids obtained during nanofiltration of the fermentation broths results from the size and geometry of the separated particles. A similar relationship has been observed by other authors (Choi et al., 2008) in their studies on the removal of organic acids from wastewaters using nanofiltration membranes. For ES10 membrane (cut-off 100 Da), the rejections of succinic acid (MW = 118 Da) and citric acid, whose MW are higher than or close to the cut-off of the membrane, were very high (over 90%) irrespective of pH. This means that a reduced surface charge of the NF membrane and neutral form of the organic acids below pKa appear to limit the amount of electrostatic repulsion between the membrane and organic solute, and the sieving effect related to the molecular size of the compounds appears to have an important role. Also Van der Bruggen et al. (1999) have reported that the rejection of negatively charged organic solutes with a molecular size close to the pore size of the NF membrane was driven more by sieving than by electrostatic repulsion. The retention degree of succinic acid (118 Da) and citric acid are higher than that of fumaric acid one, while the retention degree of acetic acid (60 Da) is the smallest of all studied organic acids. For the ceramic membrane, the rejection of acetic acid is 69%, implying that the separation mechanism of this acid by the NF membrane
Table 2 Retention and composition of retentate of fermentation components during NF process. Fermentation broth
I II
Concentration (g/L) I II
Retention (%) MPa
Fum
Suc
Cit
Ac
Cor
Gly
[Cl]
1.4* 0.8 1.2 1.4
79.0 95.2 94.3 92.3
100.0 – – –
99.0 100.0 100.0 100.0
68.9 – – –
– 100.0 100.0 100.0
5.7 12.8 11.4 11.5
42.4 – – –
1.4* 0.8 1.2 1.4
2.38 2.78 2.95 3.71
0.17 – – –
0.04 0.19 0.19 0.28
0.21 – – –
– 2.67 2.55 3.23
Fum – fumaric acid, Suc – succinic acid, Cit – citric acid, Ac – acetic acid, Cor – cordycepic acid, Gly – glycerol, [Cl] – chloride anions. * Results from Staszak et al. (2014).
0.08 0.62 0.67 0.43
0.29 – – –
K. Prochaska et al. / Bioresource Technology 167 (2014) 219–225
may involve only electrostatic repulsion due to molecular size much smaller than the cut-off of the NF membrane. The observed retention of the uncharged component – glycerol – is very low (below 13%). This result can be explained by the absence of steric hindrance effects and electrostatic interactions. A similar observation has been described in literature (Van der Bruggen et al., 2006). Moreover, it has been shown that the presence of mineral salts causes a decrease in the process selectivity. The results obtained indicate that nanofiltration could be applied as one of the purification and concentration steps for the separation of fermentation components.
4.3. Bipolar electrodialysis of fermentation broths In the second step, the bipolar electrodialysis of fermentation broth after nanofiltration pre-treatment was investigated. The process was performed under a constant electric field at 120 A/m2 of current density for 2.5 h. Fig. 3 illustrates the changes in concentration of the fermentation components in diluate chamber, between the beginning of the EDBM process (t = 0 h) and at its end (t = 2.5 h). The concentrations of fumaric acid and succinic acid in diluate compartment were changed during bipolar electrodialysis of fermentation broth I, while the concentrations of other components remained constant. This selective separation of dicarboxylic acids was achieved by the anion-exchange membrane (PC 200D) and the stack configuration applied. The effect of cell configurations on the performance of organic acids production by EDBM process has been described by other authors (Huang et al., 2007). It should be noted that only BP-AM stack configuration makes it possible to investigate the competition between the acidic anions. The transport of citric acid and acetic acid through the anionexchange membrane is limited due to the geometries and the structures of these compounds, which differ significantly from the geometry and structure of dicarboxylic acid. Wang et al. (2011) have indicated that the type of acid species and the transport number of acid anions in the anion-exchange membrane were responsible for the permselectivity differences. Furthermore, a small amount of chloride anions was found to be able to pass through the membrane due to the anion small size and high mobility. The chloride transport could be also explained by incomplete exclusion of small ions, because ion-exchange membranes are not perfectly selective (Wilhelm et al., 2001). The results obtained in EDBM process of broth I are compared with those obtained in bipolar electrodialysis of broth II.
Fig. 3. Changes in concentration of fermentation components in the diluate chamber vs. time of bipolar electrodialysis.
223
On the basis of the results obtained, the current efficiency (CE), the energy consumed for 1 kg of fumaric acid produced (E) and the recovery ratio of fumaric acid (gFUM) were calculated. CE is equal to 0.74% and 0.67%, E 7.9 and 7.3 kWh/kg, gFUM 41.4% and 38.5% for fermentation broth I and II, respectively. The lowest value of fumaric acid recovery ratio (38.5%) was obtained in bipolar electrodialysis of fermentation broth II. The transport of fumarate anions can be limited by the competitive diffusion of cordycepic anions. It should be also pointed out that this competitive diffusion considerably decreases the current efficiency (Tongwen and Weihua, 2002). In the experiments, pH-values were changed from 6.2 to 12.4 (Fig. 4). Taking into account the dissociation constants of fumaric (pKa1 = 3.02, pKa2 = 4.38) and cordycepic acids (pKa = 11.5), the transport of fumarate anions is possible beginning from pH above 6, but when pH of the diluate solution reaches 11, cordycepic anions can also permeate across the membrane. The energy consumed for 1 kg of fumaric acid produced was higher for bipolar electrodialysis of broth I. The energy consumption is significantly affected by the cell voltage and by the amount of produced fumaric acid, as shown in Eq. (3). However, the differences in energy consumption can be also related to the different compositions of the broths. The presence of additional charge carriers like chloride, citrate ions, etc., could be responsible for reduction of overall resistance (Fig. 4). However, the voltage drop for both fermentation broths during bipolar electrodialysis process is similar, owing to minor differences in the value of the broth ionic strength (lbroth_I = 0.069, lbroth_II = 0.047). To sum up, bipolar electrodialysis can be used as the second step of selective separation and concentration of fumaric acid from the broth. As a result of bipolar electrodialysis of fermentation broth, a 61% recovery of fumaric acid was obtained. It should be noted that in the EDBM process, fumaric acid can be concentrated and isolated from the other components like acetic acid, citric acid, mineral salts as well as unreacted glycerol. It is also found that the composition of the broth has a significant influence on the recovery ratio and energy consumed in the process. 4.4. Reactive extraction of fermentation broths The most important features that determine the attractiveness of the liquid–liquid extraction as a separation technique are as follows: a wide range of technical and technological solutions, the possibility of solute separation from low concentrated or unconventional solutions, high purity of products, solute recovery
Fig. 4. The overall voltage drop and changes in pH-value in the diluate chamber vs. time of bipolar electrodialysis of the fermentation broths studied.
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from waste streams, secondary sources and the possibility of byproduct recovery (Kurzrock and Weuster-Botz, 2010; Rydberg et al., 2004). These advantages have prompted the choice of the extraction method for fumaric acid recovery. As follows from literature, the reactive extraction with organophosphorus extractants, aliphatic amines or quaternary ammonium salts has been successfully applied for separation of a vast variety of carboxylic acids (Kertes and King, 2009; Labbaci et al., 2010; Wis´niewski and Pierzchalska, 2005; Yang et al., 2013), i.e. lactic, propionic, succinic, maleic, oxalic, acetic, etc. Prior to the three-step extraction of fumaric acid from the solutions left after the fermentation broth processing, some solvating (TBP and Cyanex 923) or basic (TOA and Aliquat 336) extractants were screened for fumaric acid removal from the feed at various initial pH values. Aliquat 336 (basic extractant) and Cyanex 923 (solvating extractant) were selected from the extractants studied (Table 3) as the most effective for fumaric acid removal. Although TBP seems to extract fumaric acid similarly to Cyanex 923, it was not chosen for further investigation because of its relatively high solubility in water (280 mg/L at 25 °C) and tendency to hydrolyze (Kertes and Halpern, 1961). As Aliquat 336 extracts from 40% to 70% fumaric acid at pH range from 2 to 9, it means that both forms, i.e. fumaric acid and fumarate, can be extracted efficiently with this quaternary ammonium salt. Such an efficient extraction can be attributed to the following reactions of the acid (H2Fum) with the extractant (R4N+Cl) (Kyuchoukov and Yankov, 2005):
2ðR4 Nþ Cl Þorg þ H2 Fumaq $ ð2½R4 Nþ Cl : H2 FumÞorg
ð6Þ
þ 2 2ðR4 Nþ Cl Þorg þ Fum2 aq $ ð½R4 N 2 Fum Þorg þ 2Claq
ð7Þ
Kyuchoukov and Yankov (2005) have indicated that the concentration ratio between the extracted undissociated molecules and dissociated anions depended not only on pH but also on the total concentration of the acid in the aqueous phase. Although, their studies concerned the extraction from aqueous solutions with a high content of chlorides, it seems that also for the solutions studied in this work (chloride concentration 0.1 mol/L) the molar ratio of the complex made by fumaric acid:Aliquat 336 in the organic phase is close to 1:2. As 0.05 mol/L fumaric acid contains twice as much carboxylic groups, thus 0.1 mol/L extractant should extract as maximum 50% of the fumaric acid. In fact, the percentage extraction reaches 70% and probably results from formation of the other ion pairs according to the reaction (Matsumoto et al., 1999):
HFumaq þ ðR4 Nþ Cl Þorg ! ðR4 Nþ HFum Þorg þ Claq
H2 Fumaq þ 2Cyanex923org $ ðH2 Fum 2Cyanex923Þorg
ð9Þ
Thus, with increasing pH, i.e. with decreasing content of the acidic form, the extraction of fumaric acid decreases. The acid was stripped with 0.2 mol/L NaOH from the organic phase loaded at pH 2 and 6, and the efficiency of stripping exceeded 80%. Sodium fumarate formed as a result of stripping can be easily converted into fumaric acid, if necessary. The diluate and concentrate after preliminary treatment, i.e. bipolar electrodialysis process (Fig. 1), were extracted in three steps with solutions of Aliquat 336 or Cyanex 923 in octanol. Percentage extraction of fumaric acid after one, two and three extraction steps and changes in pH of the aqueous phases are shown in Table 4. Percentage extraction of fumaric acid from real solutions both with solvating (Cyanex 923) and basic (Aliquat 336) extractants is high and after three steps exceeds 85% and 70%, respectively. The three-step extraction of fumaric acid proves that the acid can be efficiently removed both from the diluate and the concentrate after bipolar electrolysis. It has been shown that the extraction efficiency with Cyanex 923 from the real solutions differs from that from the model solutions shown in Table 3. Although, the diluate pH before extraction exceeds 12 (Table 4), the percentage extraction of fumaric acid even after one step of extraction reaches 70%. Compared with the model solution of pH 9 and only 20% extraction of the acid, it is obvious that the presence of other species in the real solution enhances the fumarate extraction. The efficiency of the three-step extraction with both extractants from the concentrate yields almost 100%. It is enhanced by acidic pH definitely lower in the concentrate (initially equal to even 2.3) than in the diluate (initial pH above 12). After each step of extraction, the pH of the concentrate increases from the initial pH 2.3 to 7.4 as a result of fumaric acid Table 4 Changes in extraction efficiency and pH after 1, 2 and 3 stage of fumaric acid extraction with 0.1 mol/L Cyanex 923 or Aliquat 336 in octanol from the diluate and the concentrate obtained in bipolar electrodialysis. Diluate
E1 E1+2 E1+2+3 pH0 pH1 pH2 pH3
Concentrate
Cyanex 923
Aliquat 336
Cyanex 923
Aliquat 336
72 79 86 12.8 12.3 12.3 11.9
30 52 71 12.8 11.6 11.5 11.4
62 90 98 2.3 5.6 6.8 7.3
71 91 97 2.3 6.7 7.0 7.1
ð8Þ
or partial participation of octanol in the extraction (Tamada and King, 1990). On the other hand, solvating extractants, e.g. Cyanex 923, transport the acid to the organic phase as a result of the acid molecule solvation (Starr and King, 1992):
Table 3 Dependence of the extraction efficiency of fumaric acid on the initial pH of the model feed solution (C0 = 1.2 g/L, i.e. 0.1 mol/L) for various organic solutions of 0.1 mol/L extractants in octanol. Type of extractant
Aliquat 336 TOA TOA + TBP TBP Cyanex 923
EFum (%) pH 2
pH 6
pH 9
61 13 13 72 71
45 6 17 18 35
57 7 5 45 15
Fig. 5. Three step extraction efficiency of fumaric acid with 0.1 mol/L Aliquat 336 in octanol from the retentate obtained in NF process.
K. Prochaska et al. / Bioresource Technology 167 (2014) 219–225
concentration decrease in the aqueous phase (Table 4). On the other hand, pH of the diluate after extraction does not change significantly and is still basic near 12, which means that fumaric acid is extracted from the diluate as a fumarate. Fumaric acid extraction from nanofiltration retentate is not as effective as from electrodialysis diluate and concentrate (Fig. 5). Initial pH of the retentate before extraction is 6.5 and does not change significantly after the three-step extraction. At this pH identification of a single extraction mechanism is hardly possible because of the presence of various forms of fumaric acid in the aqueous solution that affects the extraction efficiency. However, it is clear that in all cases the three-step extraction and stripping can support membrane techniques to separate dicarboxylic acid from the fermentation broth. 5. Conclusion A novel approach based on a hybrid system permitting the performance of nanofiltration, bipolar electrodialysis and reactive extraction is proposed for the recovery of fumaric acid from the fermentation broths resulting from bioconversion of glycerol. This hybrid system enables fumaric salt to be concentrated even up to 95% (depending on TMP), to be further converted to fumaric acid with AM BM stack in EDBM process. Finally, fumaric acid can be removed in a three-step reactive extraction with commercial extractants even at 90% efficiency. Extraction and stripping can support membrane techniques to separate efficiently dicarboxylic acid from the fermentation broth. Acknowledgements This research was financially supported within the project ‘‘Biotechnological conversion of glycerol to polyols and dicarboxylic acids,’’ implemented within the Operational ProgrammeInnovative Economy, 2007–2013, co-financed by the European Union. PO IG 01.01.02.074/09. References Bouchoux, A., Roux-de Balmann, H., Lutin, F., 2006. Investigation of nanofiltration as a purification step for lactic acid production processes based on conventional and bipolar electrodialysis operations. Sep. Purif. Technol. 52, 266–273. Choi, J.-H., Fukushi, K., Yamamoto, K., 2008. A study on the removal of organic acids from wastewaters using nanofiltration membranes. Sep. Purif. Technol. 59, 17– 25. Da Silva, A.H., Miranda, E.A., 2013. Adsorption/desorption of organic acids onto different adsorbents for their recovery from fermentation broths. J. Chem. Eng. Data 58, 1454–1463. Deng, Y., Li, Y., Xu, Q., Gao, M., Huang, H., 2012. Production of fumaric acid by simultaneous saccharification and fermentation of starchy materials with 2deoxyglucose-resistant mutant strains of Rhizopus oryzae. Bioresour. Technol. 107, 363–367. _ _ ´ ska, A., Czaczyk, K., Pawlicka, J., 2010. The use of high performance liquid Drozdzyn chromatography (HPLC) for determination of polyols in fermentation broth. Aparatura Badawcza i Dydaktyczna 4, 121–128. Huang, C., Xu, T., Zhang, Y., Xue, Y., Chen, G., 2007. Application of electrodialysis to the production of organic acids: state-of-the-art and recent developments. J. Membr. Sci. 288, 1–12. Kang, S.H., Chang, Y.K., 2005. Removal of organic acid salts from simulated fermentation broth containing succinate by nanofiltration. J. Membr. Sci. 246, 49–57. Kang, S.H., Chang, Y.K., Chang, H.N., 2004. Recovery of ammonium lactate and removal of hardness from fermentation broth by nanofiltration. Biotechnol. Prog. 20, 764–770.
225
Kertes, A.S., Halpern, M., 1961. Hydrochloric acid promoted hydrolysis of tri-n-butyl phosphate. J. Inorg. Nucl. Chem. 20, 117–126. Kertes, A.S., King, J., 2009. Extraction chemistry of fermentation product carboxylic acids. Biotechnol. Bioeng. 103, 432–444. Kordowska-Wiater, M., Polak-Berecka, M., Was´ko, A., Targon´ski, Z., 2012. Protoplast fusion of Rhizopus oryzae and Rhizopus microsporus for enhanced fumaric acid production from glycerol. J. Biotechnol. Comput. Biol. Bionanotechnol. 93, 425– 430. Kurzrock, T., Weuster-Botz, D., 2010. Recovery of succinic acid from fermentation broth. Biotechnol. Lett. 32, 331–339. Kyuchoukov, G., Yankov, D., 2005. Mechanism of lactic acid extraction with quaternary ammonium chloride (Aliquat 336). Ind. Eng. Chem. Res. 44, 5733– 5739. Labbaci, A., Kyuchoukov, G., Albet, J.L., Molinier, J., 2010. Detailed investigation of lactic acid extraction with tributylphosphate dissolved in dodecane. J. Chem. Eng. Data 55, 228–233. Luo, J., Wan, Y., 2013. Effects of pH and salt on nanofiltration – a critical review. J. Membr. Sci. 438, 18–28. Matsumoto, M., Takagi, T., Nakaso, T., 1999. Extraction equilibria of organic acids with tri-n-octylmethylammonium chloride. Solvent Extr. Res. Dev. Jpn. 6, 144– 150. Nakajima-Kambe, T., Nozue, T., Mukouyama, M., Nakahara, T., 1997. Bioconversion of maleic to fumaric acid by pseudomonas alcaligenes Strain XD-1. J. Ferment. Bioeng. 84, 165–168. Rydberg, I., Cox, M., Musicas, C., Choppin, G.R., 2004. Solvent Extraction and Practice. Taylor & Francis, New York. Song, C.W., Kim, D.I., Choi, S., Jang, J.W., Lee, S.Y., 2013. Metabolic engineering of Escherichia coli for the production of fumaric acid. Biotechnol. Bioeng. 110, 2025–2034. Starr, N.J., King, C.J., 1992. Water-enhanced solubility of carboxylic acids in organic solvents and its application to extraction processes. Ind. Eng. Chem. Res. 31, 2572–2579. Staszak, K., Woz´niak, M.J., Karas´, Z., Staniewski, J., Prochaska, K., 2013. Application of nanofiltration in the process of the separation of model fermentation broths components. Pol. J. Chem. Technol. 15, 1–4. Staszak, K., Woz´niak, M., Sottek, M., Karas´, Z., Prochaska, K., 2014. Removal of fumaric acid from simulated and real fermentation broth. J. Chem. Technol. Biotechnol. http://dx.doi.org/10.1002/jctb.4311. Tamada, J.A., King, C.J., 1990. Extraction of carboxylic acids with amine extractants. 2. Chemical interactions and interpretation of data. Ind. Eng. Chem. Res. 29, 1327–1333. Tongwen, X., Weihua, Y., 2002. Effect of cell configurations of the performance of citric acid production by a bipolar membrane electrodialysis. J. Membr. Sci. 203, 145–153. Van der Bruggen, B., Schaep, J., Wilms, D., Vandecasteele, C., 1999. Influence of molecular size, polarity and change on the retention of organic molecules by nanofiltration. J. Membr. Sci. 156, 29–41. Van der Bruggen, B., Verliefde, A., Braeken, L., Cornelissen, E.R., Moons, K., Verberk, J.Q.J.C., van Dijk, H.J.C., Amy, G., 2006. Assessment of a semi-quantitative method for estimation of the rejection of organic compounds in aqueous solution in nanofiltration. J. Chem. Technol. Biotechnol. 81, 1166–1176. Wang, Y., Zhang, N., Huang, C., Xu, T., 2011. Production of monoprotic, diprotic, and triprotic organic acids by using electrodialysis with bipolar membranes: effect of cell configurations. J. Membr. Sci. 385–386, 226–233. Wilhelm, F.G., Punt, I., Van der Vegt, N.F.A., Wessling, M., Strathmann, H., 2001. Optimisation strategies for the preparation of bipolar membranes with reduced salt ion leakage in acid–base electrodialysis. J. Membr. Sci. 182, 13–28. Wis´niewski, M., Pierzchalska, M., 2005. Recovery of carboxylic acids C1–C3 with organophosphine oxide solvating extractants. J. Chem. Technol. Biotechnol. 80, 1425–1430. Xu, Q., Li, S., Fu, Y., Tai, C., Huang, H., 2010. Two-stage utilization of corn straw by Rhizopus oryzae for fumaric acid production. Bioresour. Technol. 101, 6262– 6264. Yang, G., Sarwar Jahan, M., Ahsan, L., Zheng, L., Ni, Y., 2013. Recovery of acetic acid from pre-hydrolysis liquor of hardwood kraft-based dissolving pulp production process by reactive extraction with triisooctylamine. Bioresour. Technol. 138, 253–258. Zhang, J., Tang, L., Zhang, H., Yang, Y., Mao, Z., 2012. A novel and cleaner technological process of extracting L-glutamic acid from fermentation broth by two-stage crystallization. J. Cleaner Prod. 20, 137–144. Zhao, W., Sun, X., Wang, Q., Ma, H., Teng, Y., 2009. Lactic acid recovery from fermentation broth of kitchen garbage by esterification and hydrolysis method. Biomass Bioenergy 33, 21–25.