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Metabolic and Process Engineering of Clostridia for Biofuel Production

Jiang, Wenyan
http://rave.ohiolink.edu/etdc/view?acc_num=osu1400696231

Abstract Details

2014, Doctor of Philosophy, Ohio State University, Molecular, Cellular and Developmental Biology.
Recently, with the concerns of unstable crude oil supply, rapid increase in gasoline prices and severe climate changes, higher alcohols (alcohols with more than two carbons) have gained interests for their potentials in replacing petroleum as new generation transportation fuels. Among all these candidates, n-butanol as a four carbon solvent has received the most attention because it shares very similar characteristics with gasoline and can be naturally produced by solventogenic Clostridia via Acetone-Butanol-Ethanol (ABE) fermentation. However, butanol production by these native producers suffers from low titer and yield due to inefficient substrate conversion and butanol cytotoxicity upon cell growth and metabolism. Also, the necessity of generating byproducts during fermentation significantly reduces butanol titer and product selectivity, and therefore, increases the cost for butanol recovery through distillation. In order to commercialize biobutanol as economically as petroleum-based processes, a more optimized overall fermentation strategy is highly desirable. Therefore, the goal of this study was to establish cost-effective fermentation processes for higher alcohols production through various approaches, including inexpensive feedstock utilization, process optimization employing external driving forces, and new strain development. First, the stability of hyper-butanol-producing strain Clostridium acetobutylicum JB200 was validated by long-term repeated batch fermentation with cells immobilized in a fibrous bed bioreactor using sucrose as substrate. Its stable fermentation performance using low-cost sugarcane juice with a high butanol titer (16—20 g/L), yield (~0.21 g/g sucrose) and productivity (~0.32 g/L•h) indicated that JB200 is a promising strain for industrial application. Then, the effect of extra driving forces provided by artificial electron carrier addition on butanol production by metabolically engineered Clostridium tyrobutyricum strain CtΔack-adhE2 was studied. The results suggested that artificial electron carriers can remarkably increase butanol titer and yield, while reduce the generation of byproducts. In addition, metabolic engineering of acidogenic C. tyrobutyricum were conducted to examine its feasibility as an isopropanol producer. A final isopropanol titer of 4.28 g/L in free-cell fermentation was achieved and an in vivo fluorescence based gene expression reporter system was developed to facilitate future gene manipulation in C. tyrobutyricum and other anaerobic microorganisms. This project demonstrated that by applying low-cost substrates, extra driving power as well as strains with high fermentation performance, the input-output ratio of butanol production via fermentation can be further enhanced to compete with petroleum-based processes. Meanwhile, for isopropanol production, more studies of solvent-producing gene regulation, speed-limiting-step enzyme activities, and redox balance in C. tyrobutyricum are still required.
Shang-Tian Yang, Dr. (Advisor)
Jeffrey Chalmers, Dr. (Committee Member)
Robert Tabita, Dr. (Committee Member)
Robert Lee, Dr. (Committee Member)
232 p.
Chemical Engineering
Biofuels, butanol, isopropanol, fermentation

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Citations

  • Jiang, W. (2014). Metabolic and Process Engineering of Clostridia for Biofuel Production [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1400696231

    APA Style (7th edition)

  • Jiang, Wenyan. Metabolic and Process Engineering of Clostridia for Biofuel Production. 2014. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1400696231.

    MLA Style (8th edition)

  • Jiang, Wenyan. "Metabolic and Process Engineering of Clostridia for Biofuel Production." Doctoral dissertation, Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1400696231

    Chicago Manual of Style (17th edition)

osu1400696231
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This open access ETD is published by The Ohio State University and OhioLINK.