Current Perspective of Sustainable Surfactants Based on Renewable Building Blocks

Journal Pre-proof Current Perspective of Sustainable Surfactants Based on Renewable Building Blocks Avinash Bhadani, Ananda Kafle, Taku Ogura, Masaaki Akamatsu, Kenichi Sakai, Hideki Sakai, Masahiko Abe PII:

S1359-0294(20)30004-2

DOI:

https://doi.org/10.1016/j.cocis.2020.01.002

Reference:

COCIS 1337

To appear in:

Current Opinion in Colloid & Interface Science

Received Date: 13 June 2019 Revised Date:

18 January 2020

Accepted Date: 20 January 2020

Please cite this article as: Bhadani A, Kafle A, Ogura T, Akamatsu M, Sakai K, Sakai H, Abe M, Current Perspective of Sustainable Surfactants Based on Renewable Building Blocks, Current Opinion in Colloid & Interface Science, https://doi.org/10.1016/j.cocis.2020.01.002. This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2020 Published by Elsevier Ltd.

CO2 + H2O + organic and inorganic degradation products

Derivatization of renewable feedstock into different chemicals



Renewable Feedstocks

Biodegradation

Biodegradation by microbes, enzymes etc. present in environment

Sustainable Cycle for Surfactant Manufacturing

Sustainable Surfactant

Renewable building blocks: fatty acids, fatty alcohols, fatty amines, terpenes, sugars, amino acids etc.

Chemical conversion or bio-conversion into surfactants



Current Perspective of Sustainable Surfactants Based on Renewable Building Blocks Avinash Bhadani,*1 Ananda Kafle,2 Taku Ogura,1 Masaaki Akamatsu,2 Kenichi Sakai,1,2 Hideki Sakai,1,2 Masahiko Abe*1 1

Research Institute for Science and Technology, Tokyo University of Science, 2641

Yamazaki, Noda, Chiba 278-8510, Japan. 2

Department of Pure and Applied Chemistry, Tokyo University of Science, 2641

Yamazaki, Noda, Chiba 278-8510, Japan. Tel and Fax: +81-4-7121-2439. *Corresponding Authors: Prof. Masahiko Abe and Dr. Avinash Bhadani E-mail: (1) [email protected] (2) [email protected]

Abstract Surfactants are active or essential ingredient of several industrial and consumer formulations. These amphiphilic organic molecules demonstrate unique ability to adsorb at interface and self-aggregate or self-assemble into different phases in aqueous or non-aqueous solution. In recent years, environmental concerns coupled with

increased

consumer

awareness

have

guided

substantial

growth

of

environmentally benign surfactant molecules often termed as ‘green surfactants’, oleo-chemical based surfactants’, ‘renewable surfactants’ ‘bio-surfactants’, ‘natural surfactants’ etc. These groups of new generation of ecofriendly surfactant molecules often directly or indirectly derived/developed from renewable building blocks can be

1

broadly termed as ‘sustainable surfactants’ which are increasingly becoming popular in many application areas. The ever-increasing demand of surfactants in several application areas necessitates development of many new structural analogues of these molecules by sustainable approach. This review summarizes recent progress in the area of sustainable surfactants, their potential impact and future perspective.

Key words: Sustainable surfactant; Bio-surfactant; Green surfactant; Renewable building block; Biodegradable. 1. Introduction Surfactant molecules owning to their characteristic amphiphilic nature demonstrate unique interfacial and self-assembly properties. These surface-active compounds are able to self-aggregate in both polar and nonpolar solvent system and hence are used as emulsifiers, dispersants, wetting agents and foaming agents in countless industrial and consumer products [1]. These surfactants were principally classified into four different categories depending upon their molecular structure i.e. anionic surfactants [2], cationic surfactants [3], non-ionic surfactants [4] and amphoteric/zwitterionic surfactants [5]. However with the emergence of many versatile and diverse molecular designs of above-mentioned principal varieties, the modern day surfactant molecules are sometimes sub-classified into different varieties such as: gemini surfactants [6] and polymeric surfactants [7]. Apart from these general categories mentioned-above there are also some special categories of surfactants such as stimuli-responsive surfactants [8] and hybrid surfactants [9], which demonstrate unique and distinct physico-chemical properties compared to traditional surfactants. Conventional surfactants are generally derived or manufactured using petrochemical feedstock or combination of renewable and petrochemical feedstock. However the

2

current trend suggests increasing awareness and positive consumer perception about surfactants manufactured using renewable raw materials [10]. The newly adopted resolution by United Nations in seventieth session of the United Nations General Assembly focused on sustainable development plan [11]. The declaration focused on agenda for sustainable development for the years to come with necessity for developing future technologies based on sustainable chemistry and engineering [12]. Surfactant being one of the most widely used chemical products also needs to be developed via sustainable approach to lower the carbon footprint and reduce the dependence on petrochemicals. Surfactants are not just active and necessary ingredient for most of the consumer products such as detergents, fabric softeners, cleaning formulation, shampoo formulation, hair care formulation, oral care compositions, cosmetic formulations etc., but bulk of them are also used in several engineering and industrial manufacturing sector such as: pulp and paper processing; fiber and textile manufacturing; metal and mineral processing; food processing; pigments, paints and coatings industries; crude oil production; petroleum and lubricant industry etc [13,14]. In pharmaceutical industries surfactants are important constituent of several transdermal topical formulations, medicinal compositions, and drug and gene delivery system [15-18]. The increasing demand of various types of surfactants in innumerable application areas necessitates development of several new varieties of sustainable surfactant molecules utilizing renewable building blocks [19]. Figure 1 shows ideal sustainable cycle for surfactant manufacturing where chemicals derived from natural sources can be utilized for developing new generation of surfactant molecules. These surfactants upon biodegradation would be able to release quantitative carbon, which have been previously utilized by plants to build renewable feedstocks.

3

CO2 + H2O + organic and inorganic degradation products

Derivatization of renewable feedstock into different chemicals

Renewable Feedstocks

Sustainable Cycle for Surfactant Manufacturing

Biodegradation

Biodegradation by microbes, enzymes etc. present in environment

Sustainable Surfactant

Renewable building blocks: fatty acids, fatty alcohols, fatty amines, terpenes, sugars, amino acids etc.

Chemical conversion or bio-conversion into surfactants

Figure 1: Ideal sustainable cycle for developing new generation of sustainable surfactants.

2. Conventional choice of building blocks for production of surfactants and emerging sustainable alternatives: The raw material for manufacturing surfactants are derived from both non-renewable sources such as petrochemical feedstock, as well as renewable plant based feedstocks. Renewable feedstocks used as starting material for synthesis of surfactants often face severe economic competition from inexpensive petrochemical derived hydrocarbons and hence the later are economically preferred choice as starting material for synthesis of majority of conventional surfactants. However new generation of surfactant molecules developed from renewable building blocks are increasingly becoming popular

because

of

their

desirable

properties

such

as

biodegradability,

biocompatibility and absence of toxicity [20]. Surfactants are principally composed of two molecular parts, which are hydrophobic alkyl tail part, and an hydrophilic head part often termed as hydrophilic headgroup.

4

These two distinct organic moieties i.e. ‘hydrophobic tail part’ and ‘hydrophilic headgroup’ connected by chemical bond demonstrates unique amphiphilic nature. The most common hydrophobic part for manufacturing surfactants is fatty alcohols with a chain length ranging from C10 to C18. These fatty alcohols are used for manufacturing commercial surfactants such as alcohol ethoxylates, ethoxysulphates, fatty alcohol sulfonates etc. The other important surfactant precursors are different fatty acids and its derivatives such as fatty acid chlorides, fatty acid anhydrides, fatty amines etc. A bulk of the fatty acid derivatives being used for surfactant manufacturing comes from renewable triglycerides. However the fatty alcohols that are the principal precursor for the surfactant industry are derived both from petrochemicals as well as renewable fatty acids. Surfactant manufacturers in United States use considerable quantity of petrochemical based fatty alcohols for surfactant manufacturing [21]. In recent years efforts are in place to increase the market share of naturally derived/manufactured fatty alcohol based surfactants in house hold detergents, dishwashers etc. There are emerging trend of using unconventional naturally occurring branched hydrophobic chains for the development of new amphiphilic molecules [22,23]. There are also counter views about using renewable plant based oils for manufacturing surfactants especially when the plant oils are already being utilized for manufacturing bio-fuels apart from being used for human consumption. The more demand for such oils are leading to continuous increase in oil prices. As a result the scientific community is also suggesting microbial lipids as an alternative sources of clean sustainable building blocks for bio-surfactants manufacturing [24,25]. However waste cooking oils and different types of non-edible oils containing different fatty acids can be considered as good source for the hydrophobic portion of the surfactant molecule

5

[26]. The hydrophilic part of sustainable surfactants is mainly composed of naturally occurring building blocks such as different form of sugars and its derivative, glycerol and its derivative, different types of amino acids etc. 3. Environmental impact of embracing sustainable surfactants: Utilizing the renewable building blocks for surfactant manufacturing also helps in reducing the CO2 emissions since the renewable surfactants after degradation only releases back the quantitative amount of carbon to the environment that has been previously consumed by plant for manufacturing renewable building blocks. On the other hand the use of petrochemical feedstocks for surfactant manufacturing ensures release of entrapped carbon, which contribute to increase in greenhouse gases [10]. In contrast to the general mentioned above, there are also conflicting views regarding the sustainable development of surfactants utilizing renewable building blocks. The C12 to C18 hydrocarbons coming from tropical oils such as palm kernel and coconut oil are often considered as renewable building blocks for manufacturing surfactants, however these tropical plants are cultivated by removing the natural rain forests and their wild inhabitants [27]. Resolution adopted by the General Assembly also call to improve water quality by reducing pollution, eliminating dumping and minimizing release of hazardous chemicals in land, air and water [12]. Surfactants which is the most abundantly used chemical commodity not only needs to be designed using renewable and sustainable approach but also smartly designed so that it can be easily degraded in environment after its use. Chemicals including surfactants containing certain functional groups such as ester functionality undergo biodegradation with ease compared to synthetic chemicals and surfactants [28,29]. This is essentially because numerous varieties of esterase enzymes are already present in the environment and these enzymes ensure good biodegradation of any substrate containing ester linkage

6

[30]. In recent years several new type of surfactants have been developed containing ester functional group with an aim to address the biodegradation concern of certain group of surfactants [31-37]. 4. Emerging renewable building blocks for surfactant production and new molecular design of sustainable surfactants.

(i) Sustainable headgroups for surfactants: The hydrophilic headgroups of sustainable surfactants can be designed utilizing several different natural molecules such as glycerol, amino acids, sugars etc. and their respective derivatives. Glycerol, which is abundantly available from fat splitting process as well as from biodiesel manufacturing, can be efficiently converted into different types of chemicals including surfactants [38-41]. New glycerol based anionic and zwitter-ionic surfactants are developed as a potential alternative to conventional sulfate and betaine surfactant [42]. Twin tail glycerol based non-ionic surfactants show good surface and interfacial properties. These surfactants demonstrate excellent oil in water and water in oil emulsifying properties [43]. Glyceric acid, which can be derived from glycerol by bioconversion using Gluconobacter frateurii bacteria is used as starting material for the synthesis of ester based green surfactants having different hydrophobic tail length. These bio-based surfactants demonstrated better emulsifying properties compared to standard SDS and monolaurin [44]. Several different structural analogues of glycerol-based surfactants are developed via direct etherification of glycerol and dodecanol using heterogeneous interfacial acidic catalysts. Physicochemical evaluation and laundry tests of these surfactants were found to be at-par with commercially available surfactant [45]. Bio-based dialkyl glycerol ethers are another group of amphiphilic compounds based on glycerol backbone. These

7

molecules are able to act as solubilizers for hydrophobic dye in aqueous medium and hence demonstrate good solvo-surfactant properties [46]. Selective acetalization of diglycerol with n-octanal catalyzed by ZnCl2 produces diglycerol monoacetal based nonionic surfactants having good surfactant properties [47].

Several new types of sustainable surfactants based on isosorbide and isomannide moiety have been synthesized and investigated for their surfactant properties (Figure 2) [48-52]. The isosorbide and isomannide is a bicyclic oxygen-containing heterocyclic compound derived from dehydration of sorbitol and mannitol respectively. Renewable isomannide-based surfactants were synthesized starting from mannitol and fatty acids (decanoic, lauric, myristic, palmitic, stearic and oleic acids).

Figure 2: Molecular structure of sustainable surfactants developed from isosorbide and isomannide moiety.

8

Environmental benign synthetic protocol is adapted to synthesize these surfactants using highly efficient and reusable heterogeneous SO3H-carbon catalyst. Synthesized surfactants were evaluated for their surface-active properties. These surfactants demonstrated very good surface activity as they were able to reduce the surface tension of water (γCMC) ranging from 25.79 to 44.14 mN m-1, depending on hydrphobic tail length of the surfactant molecules [48]. Sodium dodecyl isosorbide sulfates, which is anionic surfactants containing an isosorbide moiety is synthesized in two isomeric forms and investigated for their surfactant properties. These two isomeric surfactant molecules significantly differ from one another and demonstrate significantly different physicochemical properties in aqueous solution as they have different Krafft temperatures as well as CMC values [49]. Further research has established that the mixture of isosorbide based nonionic and anionic surfactants are able effectively form worm like micelles in aqueous solution [50]. Similarly, different types

of

isosorbide

based

non-ionic

surfactants:

5-O-dodecyl-2-O-

triethyleneglycolisosorbide; 5-O-dodecyl-2-O-glycerylisosorbide and 5-O-dodecyl-2O-glycerylisosorbideisosorbide are developed utilizing renewable building blocks [51]. Attempt is also made to develop isosorbide diesters and cyclodextrins based host-guest type surfactants [52]. Amino acid-based surfactants are biocompatible and biodegradable in nature. The hydrophilic headgroup of these surfactants are based on one or multiple amino acids and considered as a promising alternative to conventional synthetic surfactants [53]. In recent years several new structural derivatives of these surface-active molecules have been developed and investigated for several different application areas (Figure 3) [54-61]. These surfactants demonstrate excellent antimicrobial activity, selfaggregate at low concentration and have good surface activity [54-56]. Vesicles based

9

on mixed amino acid based surfactants offers several advantage over conventional lipid-based vesicles as they are easy to form and very stable over long period of time [57]. Amino acid-based cationic and anionic surfactant mixtures were recently investigated for their effectiveness as drug nanocarriers. The vesicles formed by the cationic and anionic serine-based surfactants were very effective in delivering anticancer drug doxorubicin in to a cancer cell model system. These surfactants demonstrate low toxicity and high cell uptake and vesicles loaded with the anticancer drug formed by these surfactants were able to effectively induce death of cancer causing cells [58].

Figure 3: Molecular structure of some of the recently developed amino acid based surfactants.

10

Recent investigations shows that the stable α-gels formed from amino acid L-arginine salt of long-chain monoalkyl phosphate are very effective in stabilizing the emulsions, hence these biocompatible surfactants can be very useful for developing different formulations for cosmetics and pharmaceutical industries [59-60]. Several new N-acyl amino acid based green surfactants are directly synthesized starting from commercially available vegetable oils (castor oil and cottonseed oil) and amino acids (glycine, alanine, and serine). These surfactants demonstrate good surface-active properties, which depend on both the structures of both amino acid as well as hydrophobic chains [61]. Sugar based surfactants are popular choice of surfactant molecules as they are biocompatible in nature and have good surface activity. Among the different types of sugar-based surfactants available in the market are alkyl polyglucosides (APG), alkyl polyxylosides (APX), sorbitan esters, saccharose esters etc. APGs are widely used surfactant molecules in personal care products as an efficient emulsifier and are one of the best available sustainable surfactants in the market. These surfactants are produced from oleochemical fatty alcohols and crystallized D-glucose [62]. Sorbitan esters are popular group of nonionic surfactants, which are used as emulsifying agents in several application areas. Newly developed ether functionalized sorbitan based surfactants can be considered homologous to ester derivatives of commercially available sorbitan surfactants. Sorbitan ethers exhibit surfactant and emulsifying properties similar to commercially available Span 20® surfactant [63]. New sugar acid based surfactant is developed in a one-pot synthesis process directly from Lpolyguluronate or whole alginate, a renewable polysaccharide extracted from brown seaweeds. The 100% bio-based compositions formed by these surfactants were investigated for their role as emulsion stabilizers in oil-in-water (O/W) and water-in-

11

oil (W/O) systems and compared with commercially available alkylpolyglycosides: Montanov 82®. The emulsifying properties of some these surfactants are better compared with the commercial molecule [64]. Another series of nonionic biosourced alkylglucuronamides surfactants with different hydrophobic chains (C8, C12, or C16) having glucosidic bond have been developed in two step synthetic process starting from glucuronic acid or glucuronolactone. The CMC values of these surfactant varied from 0.03 to 29 mM depending on hydrophobic tail length. These surfactants exhibit good foaming properties and are readily biodegradable in nature [65]. Several different types gluconamide, galactonamide, ether-linked derivatives of carbohydratebased surfactants and hydrogelators are investigated for their self-aggregation properties. These biocompatible surfactants displayed unique ability to inhibit recrystallization of ice [66]. N-methylglucamine is a bio-sourced raw material, which is currently being utilized as a sustainable starting material for developing new generation of sustainable surfactants (Figure 4) [67-72]. Several new varieties of N-methylglucamine based sustainable

surfactants

have

been

developed

and

investigated

for

their

physicochemical properties in recent years [68,69]. N-alkanoyl-N-methylglucamide – a green surfactant is developed via enzyme catalyzed solvent-free methodology. The developed bioconversion method if adopted for commercial production of this category of surfactant, will have immense benefits in terms of lower environmental impact [70]. Green glucamine-based trisiloxane surfactant has been developed and investigated for its surface properties. This surfactant is able to reduce the surfactant tension of the aqueous solution to very low value and is able to aggregate at very low surfactant concentration (γmin = 19.04 mN/m and CMC = 0.25 mmol/L). The ecofriendly siloxane surfactant also demonstrated good wettability on a low energy

12

surface and was also able to form vesicles [71]. Another type of green non-ionic surfactant consisting of glucamine backbone along with branched hydrophobic tail is developed based on the principles of green chemistry. This surfactant is able to reduce the surface tension of an aqueous solution to 35mN m−1 and is able to form micelles at a critical micelle concentration of 0.9 mmol L−1. The performance of the glucamine-based surfactant was found to be comparable to commercially available APGs [72].

Figure 4: Sustainable surfactants developed from N-methylglucamine. (ii) Sustainable hydrophobic tails for surfactants: Different kind of renewable fatty acids as well as terpene and its derivatives can be utilized for production of sustainable surfactants. Linear saturated fatty acids are precursors for wide variety of surfactant molecules. However the emerging trend shows increasing interest in unsaturated fatty acid such as oleic acid in development of surfactant molecules [73]. Several new structural variety of oleic acid based zwitterionic [74], anionic [75] and cationic surfactants [76] are developed and investigated for their surfactant properties. All these surfactants demonstrate excellent surfactant properties and can be

13

considered as a sustainable alternative to conventional surfactants for many application areas. Similarly, long tail betaine surfactants have been developed from renewable fatty acids such as tri-unsaturated fatty acid: linolenic acid, di-unsaturated fatty acid: linoleic acid, mono-unsaturated fatty acid: oleic acid and saturated fatty acid: stearic acid. The effect of different level of unsaturation with respect to selfassembly properties of these surfactants was investigated in detail [77]. Erucic acid is

also being considered as a renewable long chain unsaturated fatty acid for the development of sustainable surfactants [78].

Figure 5: Molecular structure of some of the renewable long saturated and unsaturated hydrophobic tail containing surfactants. Bioresource-derived erucic acid obtained from leftovers of rapeseed oil has been utilized for the synthesis of several different types of sustainable surfactants. These

14

surfactants have ultra low cmc values hence they can be every effective at lower dosages in practical application areas [79]. The broad idea behind these scientific findings encourages to utilize different kinds of long chain saturated and unsaturated fatty acids coming from waste cooking oils and other non-edible oils for the development of future generation of sustainable surfactants. Figure 5 shows some of the molecular structure of recently developed renewable long saturated and unsaturated hydrophobic tail containing sustainable surfactants [74-79]. In recent years several new type of sustainable surfactants have been developed using different kind of terpenes, which are primary constituents of the essential oils obtained from several plants and flowers (Figure 6) [80-83]. Commercially available terpenes were successfully converted to branched hydrophobic tail containing quaternary ammonium surfactants via catalytic process. These environment friendly surfactants show surface activity similar to conventional quaternary ammonium compounds [80]. New type of terpene based sustainable surfactants were developed from naturally occurring farnesol, which is a 15-carbon acyclic sesquiterpene alcohol found in several plant species such as neroli, lemon grass, tuberose, rose, citronella etc. These surfactants show excellent surfactant activity and demonstrated unique ability to undergo isomerization and degradation into several different types of naturally occurring plant volatiles [81]. The micelles formed by these bio-inspired surfactants in aqueous solution acted as micellar chemical factories for manufacturing and control releasing various different types of plant volatiles [82]. New type of surface-active cationic amphiphiles consisting of biocompatible phytol as hydrophobic tail and imidazolium or pyridinium as headgroup were developed and investigated for their oil herding efficiency. These eco-friendly surface-active molecules demonstrated enhanced crude oil herding capability and can be utilized as a

15

green alternative to deal with crude oil spill problem. These molecules are readily biodegradable and better alternative compared to conventional chemical herders currently in practice [83].

Figure 6: Sustainable cationic surfactants developed from different types of terpene molecules. (iii) Other natural moieties for designing surfactants: Naturally occurring saponins produced by microwave-assisted extraction method from soap nuts behave like typical surfactant. The extracted saponins facilitate emulsion polymerization with almost similar performance as observed by synthetic nonionic surfactants. The saponins are readily biodegradable and nontoxic compared to synthetic surfactants and has a very low CMC value [84]. Cashew nutshell liquid (CNSL), an inedible waste product of cashew nut industry offers long tail phenolic oil, is a good renewable feedstock for surfactant manufacturing [85,86]. Several new types of bio-based surfactants have been developed in recent past from the cashew nutshell liquid [87,88].

16

Cleavable vanillin-based polyoxyethylene nonionic surfactant is developed from naturally occurring edible flavor vanillin. This eco-friendly surfactant is completely biodegradable in nature as it contain cleavable acetal bond, which decompose easily under acidic conditions. The toxicity experiments established this renewable surfactant to be low-to-moderately toxic. The surface activities, wettability, emulsibility, and foaming properties of the surfactant are comparable to the commercially available nonylphenol ethoxylates surfactant [89]. Gemini sulfosuccinate surfactant developed from vegetable oil is able to significantly reduce the surface tension of aqueous system and demonstrate good emulsification capability and wetting ability. This surfactant is very effective in lubricating collagen fibers and improving physical and mechanical properties of the leather and hence this biodegradable surfactant demonstrated good fatliquoring property. Such sustainable surfactant can find application in leather processing industry [90].

5. Progress in industrial production of sustainable surfactants: In recent years surfactant manufacturer and researchers have been successful in developing many new versatile varieties of sustainable surfactants. Recently BASF and Solazyme Inc. introduced first commercial microalgae-derived betaine surfactant - Dehyton® AO 45, which is produced utilizing microalgae oils. This new commercial product is being considered as an alternative to conventional amidopropyl betaine surfactant. Dow Chemical Co. is currently offering different types of sustainable oilseed based nonionic surfactant under brand name ECOSURF™. These surfactants claim to have very low aquatic toxicity and are biodegradable in nature. BASF has introduced ethoxylated (PEG-5) rapeseed sterols in the market, which is a W/O emulsifier suitable for various W/O skin care emulsions and is currently being

17

sold by brand name Generol R E5 [91]. Procter and Gamble Co. is successfully marketing alkyl glyceryl sulfonates (AGS) for years. These surfactants with ether functionality have excellent hard water tolerance. AGS is a mild surfactant that leaves no residue and is typically used in personal care applications [27]. Further, Procter & Gamble Co. has put forward an ambitious goal to replace significant proportion of petroleum-based raw materials with sustainably sourced renewable building blocks by 2020 for the production of the surfactants and other chemicals [27]. Nonionic surfactants containing ethylene oxide units as hydrophilic headgroup constitute approximately 45 percent of total surfactant production. However the principal chemical ethylene oxide currently being used for the surfactant production in United States is derived from petrochemicals. Most recently Croda Co. introduced 100% renewable bio-based ethylene oxide in the market namely bio-EO. The precursor bio-EO is currently being produced from corn-based ethanol [92]. The company claims that the sustainable nonionic surfactant produced by utilizing bio-EO will have lower carbon footprint compared to conventional ethoxylates. Recently Evonik industries introduced new bio-surfactant and became the first company in the world to adopt biotech methods for manufacturing new generation of sustainable surfactants. The new bio-surfactant consists of well known sophorolipids and the company claims that products meets all the requirements of modern surfactants as they show good cleaning properties, are gentle on the skin, and rapidly biodegrade after use [93]. Most recently Unilever has teamed up with Evonik industries for producing renewable rhamnolipid based bio-surfactant [94]. Amino acid based surfactants are continuously increasing their market share ever since Ajinomoto Co. introduced world’s first amino acid-based surfactant in the year

18

1972 [95,96]. In recent years the rising environment concern has led to tremendous growth of these type of surfactants as they are readily biodegradable and are considered environmental friendly. Table 1 summarizes some of the commercial manufacturers of renewable surfactants. Table 1. Commercial manufactures producing sustainable surfactants. Manufacturer

Sustainable surfactant under production

BASF & Solazyme Inc.

Microalgae-derived betaine surfactant (Dehyton® AO 45)

Dow Chemical Co.

Oilseed based nonionic surfactant (ECOSURF™)

BASF

Ethoxylated rapeseed sterol surfactant (Generol R E5)

Procter and Gamble Co.

Alkyl glyceryl sulfonates (AGS)

Evonik & Unilever

Renewable rhamnolipid bio-surfactant

Evonik

Sophorolipids based bio-surfactant

Ajinomoto Co.

Amino acid based surfactants

6. Conclusions Sustainable surfactants are increasingly becoming popular and are replacing conventional petrochemical and synthetic surfactants in several different application areas. In recent years the surfactant manufacturers have launched several new ecofriendly surfactant based products in the market. The increasing consumer awareness along with obligation for the sustainable development have led to development of several new varieties of these surfactants based on renewable building blocks. These surfactants demonstrate better biodegradation properties combined with low toxicity and hence are becoming popular choice for designing new formulations for industrial and consumer use. Since the demand for the surfactant is growing at 3-4% per year. The demand for the sustainable surfactant is bound to increase in coming years. However it is very difficult to completely replace conventional surfactants manufactured from petrochemical feedstock with the new sustainable surfactants. The

19

former category of surfactants will continue to dominate consumer market because of their low cost and proven performance in many application areas. Acknowledgement Avinash Bhadani is thankful to Tokyo University of Science and Acteiive Research and Development Company, Japan for research support. References Papers of particular interest, published within the period of review, have been highlighted as: * of special interest ** of outstanding interest [1] Hargreaves T. Chemical formulation: An overview of surfactant-based preparations used in everyday life. Cambridge: Royal Society of Chemistry; 2003. [2] Hibbs J. Anionic surfactants. Chemistry and Technology of Surfactants, Farn RJ. Ed.; Blackwell Publishing Ltd; 2006. [3] Richmond JM. Cationic surfactants organic chemistry. New York: M. Dekker; 1990. [4] Os NMvan. Nonionic surfactants: Organic chemistry. New York: Marcel Dekker; 1998. [5] Domsch A. Biodegradability of amphoteric surfactants. 1995:231–54. doi:10.1007/978-94-011-1348-9_8.

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Highlights • Overview of sustainable surfactants developed utilizing renewable feedstock. • Recent advances in development of environmental friendly surfactant molecules. • Summarization of different structural derivatives of renewable surfactants and their properties. • Overall perspective of progress in development of environmentally benign surfactant molecules.

Declaration of Interests

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.