- Email: [email protected]
Construction of yeast strains for efficient ethanol fermentation from xylose by protoplast fusion
Abstracts / Journal of Biotechnology 136S (2008) S402–S459 Tao, Y.Z., Chen, Y., Wu, Y.Q., He, Y.L., Zhou, Z.H., 2007. High hydrogen yield from a two-step process of dark- and photo-fermentation of sucrose. Int. J. Hydrogen Energy 2, 200–206.
doi:10.1016/j.jbiotec.2008.07.973 V4-P-043 Construction of yeast strains for efficient ethanol fermentation from xylose by protoplast fusion Jie Li, Xinqing Zhao, Chenguang Liu, Fan Li, Jiangang Ren, Fengwu Bai ∗ Department of Bioscience and Bioengineering, Dalian University of Technology, Dalian, China E-mail address: [email protected] (F. Bai). For efficient bioconversion of lignocellulosic biomass in fuel ethanol production, yeast strains with improved productivity in the utilization of xylose are highly appreciated. In this study, xylosefermentating Candida shehatae was first subjected to ethanol adaptation, and the strain with improved ethanol tolerance was further mutagenized by UV irradiation. One respiration deficient mutant RD-5 with enhanced xylose-fermenting ability was selected. Protoplasts of RD-5 were inactivated by UV treatment before the PEG-mediated protoplast fusion with a Saccharomyces cerevisiae strain with excellent ethanol-fermenting capability. The protoplasts were regenerated on xylose plates, from which fusant F6 was demonstrated to ferment xylose to ethanol with the highest efficiency among the fusants obtained. Comparing with the parent Candida shehatae stain, the maximum ethanol production by fusant F6 was increased by 28%, with the production level of 18.75 g/L from 50 g/L xylose, and the ethanol yield was calculated to be 0.375.
References Lin, B., Zhao, X.Q., Ge, X.M., Bai, F.W., 2007. The effects of dilute acid hydrolysate by-products of corn stover on ethanol fermentation of xylose-utilizing Saccharomyces cerevisiae 6508-127. China Biotechnol. 27 (7), 61–67. Pasha, C., Kuhad, R.C., Rao, L.V., 2007. Strain improvement of thermotolerant Saccharomyces cerevisiae VS3 strain for better utilization of lignocellulosic substrates. J. Appl. Microbiol. 103 (5), 1480–1489.
doi:10.1016/j.jbiotec.2008.07.974 V4-P-044 On-line monitoring and the mechanism of the de-flocculation of flocculating yeast cells during continuous yeast culture processes Chenguang Liu, Xumeng Ge, Fengwu Bai ∗
S421
performances on ethanol production and flocculation that are crucial for the next process should be examined first. In this report, the focused laser-beam reflectance measurement (FBRM) was used in the on-line monitoring of yeast floc size distribution during the continuous yeast cell culture process. It was found that yeast cells lost flocculation ability after 20 days’ running when the bioreactor was fed by a medium containing 50 g l−1 glucose at a dilution rate of 0.12 h−1 . In addition, decrease of ethanol tolerance was also observed. A method for evaluating the flocculation of the system, mixture of SPSC01 (flocculating) and its mutant strain (non-flocculating), was established. Biomass weight and FBRM both depicted the percentage of flocculating cells. Biomass weight method was used for obtaining the concentration distribution of SPSC01 and mutant in different bioreactors so as to choose the proper interception operation. The kinetic simultaneous differential equations were proposed to explain the degeneration of the flocculation. Model parameters were evaluated through numerical calculation method and validated by experiment data. The rapid de-flocculation was attributed to high dilution rate, ineffective interception operation and low nutrition condition. The optimization technique design was advised to prevent the flocculation fading away. References Bai, F.W., Chen, L.J., Zhang, Z., Anderson, W.A., Moo-Young, M., 2004. Continuous ethanol production and evaluation of yeast cell lysis and viability loss under very high gravity medium conditions. J. Biotechnol. 110, 287–293. Bai, F.W., Anderson, W.A., Moo-Young, M., 2008. Ethanol fermentation technologies from sugar and starch feedstocks. Biotechnol. Adv. 26, 89–105. Ge, X.M., Zhao, X.Q., Bai, F.W., 2005. Online monitoring and characterization of flocculating yeast cell flocs during continuous ethanol fermentation. Biotechnol. Bioeng. 90, 523–531. Xu, T.J., Zhao, X.Q., Bai, F.W., 2005. Continuous ethanol production using selfflocculating yeast in a cascade of fermentors. Enzyme Microb. Technol. 37, 634–640.
doi:10.1016/j.jbiotec.2008.07.975 V4-P-045 Preparation, characteristics and biocompatibility of chitosanbased thermosensitive hydrogels as drug delivery system Hui Yun Zhou 1,2,∗ , Xi Guang Chen 2,∗ , Cheng Sheng Liu 2 1
The Chemical Engineering & Pharmaceutics College, Henan University of Science and Technology, Luoyang 471003, PR China 2 College of Marine Life Science, Ocean University of China, Qingdao 266003, PR China Keywords: Chitosan; ␣-GP; Thermosensitive hydrogel; Drug delivery system; Characteristics
Department of Bioscience and Bioengineering, Dalian University of Technology, Dalian, Liaoning, China
E-mail addresses: [email protected] [email protected] (X.G. Chen).
E-mail address: [email protected] (F. Bai).
Chitosan has been extensively examined in the pharmaceutical industry for its excellent biocompatibility, biodegradability, bioactivity, and nontoxicity. Chitosan solutions containing -glycerophosphate (-GP) which has temperature-controlled sol–gel transition at a temperature close to 37 ◦ C had recently been proposed as a suitable vehicle for the extravascular parenteral administration of drugs (Chenite et al., 2000; Berger et al., 2005; Cho et al., 2005). We had prepared a new thermosensitive material that could be transformed into gel at 37 ◦ C from chitosan (dissolved in acetic acid/sodium acetate buffer solution) and a mixture of ␣and -glycerophosphate (␣-GP). The thermosensitive character-
Bio-ethanol, both renewable and environmentally friendly, is believed to be one of the best alternatives to petroleum-based liquid fuels. Although continuous ethanol fermentation with selfimmobilized yeast cells which is superior to traditional ethanol fermentations has been commercialized, the energy efficiency can be further improved by increasing the ethanol concentration in the broth which is limited by the inhibition of ethanol on yeast cell growth. In an engineering view, a continuous fermentation under the condition with high ethanol can be achieved by continuously providing young yeast cells from a seed culture process. So, their
(H.Y.
Zhou),
doi:10.1016/j.jbiotec.2008.07.973 V4-P-043 Construction of yeast strains for efficient ethanol fermentation from xylose by protoplast fusion Jie Li, Xinqing Zhao, Chenguang Liu, Fan Li, Jiangang Ren, Fengwu Bai ∗ Department of Bioscience and Bioengineering, Dalian University of Technology, Dalian, China E-mail address: [email protected] (F. Bai). For efficient bioconversion of lignocellulosic biomass in fuel ethanol production, yeast strains with improved productivity in the utilization of xylose are highly appreciated. In this study, xylosefermentating Candida shehatae was first subjected to ethanol adaptation, and the strain with improved ethanol tolerance was further mutagenized by UV irradiation. One respiration deficient mutant RD-5 with enhanced xylose-fermenting ability was selected. Protoplasts of RD-5 were inactivated by UV treatment before the PEG-mediated protoplast fusion with a Saccharomyces cerevisiae strain with excellent ethanol-fermenting capability. The protoplasts were regenerated on xylose plates, from which fusant F6 was demonstrated to ferment xylose to ethanol with the highest efficiency among the fusants obtained. Comparing with the parent Candida shehatae stain, the maximum ethanol production by fusant F6 was increased by 28%, with the production level of 18.75 g/L from 50 g/L xylose, and the ethanol yield was calculated to be 0.375.
References Lin, B., Zhao, X.Q., Ge, X.M., Bai, F.W., 2007. The effects of dilute acid hydrolysate by-products of corn stover on ethanol fermentation of xylose-utilizing Saccharomyces cerevisiae 6508-127. China Biotechnol. 27 (7), 61–67. Pasha, C., Kuhad, R.C., Rao, L.V., 2007. Strain improvement of thermotolerant Saccharomyces cerevisiae VS3 strain for better utilization of lignocellulosic substrates. J. Appl. Microbiol. 103 (5), 1480–1489.
doi:10.1016/j.jbiotec.2008.07.974 V4-P-044 On-line monitoring and the mechanism of the de-flocculation of flocculating yeast cells during continuous yeast culture processes Chenguang Liu, Xumeng Ge, Fengwu Bai ∗
S421
performances on ethanol production and flocculation that are crucial for the next process should be examined first. In this report, the focused laser-beam reflectance measurement (FBRM) was used in the on-line monitoring of yeast floc size distribution during the continuous yeast cell culture process. It was found that yeast cells lost flocculation ability after 20 days’ running when the bioreactor was fed by a medium containing 50 g l−1 glucose at a dilution rate of 0.12 h−1 . In addition, decrease of ethanol tolerance was also observed. A method for evaluating the flocculation of the system, mixture of SPSC01 (flocculating) and its mutant strain (non-flocculating), was established. Biomass weight and FBRM both depicted the percentage of flocculating cells. Biomass weight method was used for obtaining the concentration distribution of SPSC01 and mutant in different bioreactors so as to choose the proper interception operation. The kinetic simultaneous differential equations were proposed to explain the degeneration of the flocculation. Model parameters were evaluated through numerical calculation method and validated by experiment data. The rapid de-flocculation was attributed to high dilution rate, ineffective interception operation and low nutrition condition. The optimization technique design was advised to prevent the flocculation fading away. References Bai, F.W., Chen, L.J., Zhang, Z., Anderson, W.A., Moo-Young, M., 2004. Continuous ethanol production and evaluation of yeast cell lysis and viability loss under very high gravity medium conditions. J. Biotechnol. 110, 287–293. Bai, F.W., Anderson, W.A., Moo-Young, M., 2008. Ethanol fermentation technologies from sugar and starch feedstocks. Biotechnol. Adv. 26, 89–105. Ge, X.M., Zhao, X.Q., Bai, F.W., 2005. Online monitoring and characterization of flocculating yeast cell flocs during continuous ethanol fermentation. Biotechnol. Bioeng. 90, 523–531. Xu, T.J., Zhao, X.Q., Bai, F.W., 2005. Continuous ethanol production using selfflocculating yeast in a cascade of fermentors. Enzyme Microb. Technol. 37, 634–640.
doi:10.1016/j.jbiotec.2008.07.975 V4-P-045 Preparation, characteristics and biocompatibility of chitosanbased thermosensitive hydrogels as drug delivery system Hui Yun Zhou 1,2,∗ , Xi Guang Chen 2,∗ , Cheng Sheng Liu 2 1
The Chemical Engineering & Pharmaceutics College, Henan University of Science and Technology, Luoyang 471003, PR China 2 College of Marine Life Science, Ocean University of China, Qingdao 266003, PR China Keywords: Chitosan; ␣-GP; Thermosensitive hydrogel; Drug delivery system; Characteristics
Department of Bioscience and Bioengineering, Dalian University of Technology, Dalian, Liaoning, China
E-mail addresses: [email protected] [email protected] (X.G. Chen).
E-mail address: [email protected] (F. Bai).
Chitosan has been extensively examined in the pharmaceutical industry for its excellent biocompatibility, biodegradability, bioactivity, and nontoxicity. Chitosan solutions containing -glycerophosphate (-GP) which has temperature-controlled sol–gel transition at a temperature close to 37 ◦ C had recently been proposed as a suitable vehicle for the extravascular parenteral administration of drugs (Chenite et al., 2000; Berger et al., 2005; Cho et al., 2005). We had prepared a new thermosensitive material that could be transformed into gel at 37 ◦ C from chitosan (dissolved in acetic acid/sodium acetate buffer solution) and a mixture of ␣and -glycerophosphate (␣-GP). The thermosensitive character-
Bio-ethanol, both renewable and environmentally friendly, is believed to be one of the best alternatives to petroleum-based liquid fuels. Although continuous ethanol fermentation with selfimmobilized yeast cells which is superior to traditional ethanol fermentations has been commercialized, the energy efficiency can be further improved by increasing the ethanol concentration in the broth which is limited by the inhibition of ethanol on yeast cell growth. In an engineering view, a continuous fermentation under the condition with high ethanol can be achieved by continuously providing young yeast cells from a seed culture process. So, their
(H.Y.
Zhou),