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Dissertation-Peng Zhang-04252018.pdf (1.88 MB)

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Optimizing Simultaneous-Isomerization-and-Reactive-Extraction (SIRE) Followed by Back-Extraction (BE) Process for Efficient Fermentation of Ketose Sugars to Products

Zhang, Peng
http://rave.ohiolink.edu/etdc/view?acc_num=toledo1524617555286546

Abstract Details

, Doctor of Philosophy, University of Toledo, Biomedical Engineering.
Lignocellulosic biomass is an abundant, inexpensive feedstock. It is mostly composed of cellulose (38-50% of the dry mass) and hemicellulose (23-32% of the dry mass). Cellulose and hemicellulose are polysaccharides that can be hydrolyzed to monosaccharides, mostly glucose and xylose. These sugars can eventually be fermented to many different products, such as ethanol and 2,3-butanediol. Fuel ethanol, which is currently produced from food-based sugars, can also be produced via fermentation of sugars derived from lignocellulosic biomass. The fermentation of xylose is essential for the cost-effective bioconversion of lignocellulose to fuels and chemicals, but wild-type strains of Saccharomyces cerevisiae do not metabolize xylose because the metabolic pathways convert xylose to xylitol via an NADPH-linked xylose reductase. Fermentation of xylose to ethanol through xylulose does occur in organisms which possess an NADH-linked aldose reductase, indicating that a balanced supply of NADH and NADPH must be maintained to avoid xylitol production. Although S. cerevisiae does not convert xylose to ethanol, it does have the metabolic pathway for the conversion of xylulose, the ketose isomer of xylose, to ethanol. Conversion of xylose to xylulose in high yield and at low cost from biomass hydrolysate has the potential to bypass the barrier to ethanol production from C5 and C6 sugars with native yeast. 2,3-Butanediol (2,3-BD) is a key building block and a promising bulk chemical due to its extensive industrial applications in making polymers, plastics, and hydrocarbon fuels. For example, 2,3-BD can be readily converted to butenes, butadiene, and methyl ethyl ketone that are used in the production of hydrocarbon fuels. Enterobacter cloacae NRRL B-23289, isolated from decaying wood/corn soil samples by the USDA Agricultural Research Service (Peoria, IL), is a natural producer of 2,3-BD. Previous work at the USDA ARS has shown that this strain is more efficient in converting ketose than aldose sugars to 2,3-BD. Particularly interesting is that fermentation of fructose showed higher 2,3-BD yield within a much shorter period of time as compared to glucose. Converting aldoses to ketoses involves isomerization, typically conducted enzymatically. However, the isomerization does not have a favorable equilibrium with respect to ketose formation. We have previously developed a method of simultaneous isomerization and reactive extraction (SIRE) to produce the ketose isomer of xylose (xylulose) in high yield and purity. SIRE-followed by back-extraction (BE) allows recovery of xylulose in nearly pure form. Although successfully implemented with low concentration xylose, SIRE has not been tested for high concentration sugars (C5 and C6 mixtures), which would be relevant for biomass hydrolysates. Optimization of SIRE-BE with high concentrations of both C5 (xylose/xylulose) and C6 (glucose/fructose) is one of the objectives of this dissertation. Using this innovative and optimized method to pretreat the aldose sugars (glucose and xylose) and produce large quantities of nearly pure, concentrated ketose sugars (fructose and xylulose), the production of 2,3-butanediol was investigated. Ketose sugar fermentation yielded more 2,3-butanediol and in a shorter time than the aldose fermentations. Using this method to produce large quantities of nearly pure, concentrated xylulose, the production of ethanol was also investigated. The native yeast produced 0.44-0.45 g ethanol/ g xylulose in xylulose fermentation.
Patricia Relue (Committee Chair)
Sasidhar Varanasi (Committee Co-Chair)
Sridhar Viamajala (Committee Member)
Stephen Callaway (Committee Member)
Randall Ruch (Committee Member)
Alternative Energy; Biomedical Engineering; Chemical Engineering

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Citations

  • Zhang, P. (2018). Optimizing Simultaneous-Isomerization-and-Reactive-Extraction (SIRE) Followed by Back-Extraction (BE) Process for Efficient Fermentation of Ketose Sugars to Products [Doctoral dissertation, University of Toledo]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1524617555286546

    APA Style (7th edition)

  • Zhang, Peng. Optimizing Simultaneous-Isomerization-and-Reactive-Extraction (SIRE) Followed by Back-Extraction (BE) Process for Efficient Fermentation of Ketose Sugars to Products. 2018. University of Toledo, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=toledo1524617555286546.

    MLA Style (8th edition)

  • Zhang, Peng. "Optimizing Simultaneous-Isomerization-and-Reactive-Extraction (SIRE) Followed by Back-Extraction (BE) Process for Efficient Fermentation of Ketose Sugars to Products." Doctoral dissertation, University of Toledo, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1524617555286546

    Chicago Manual of Style (17th edition)

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This open access ETD is published by University of Toledo and OhioLINK.