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Chemicals and Biofuels Production from CO2 and Biomass by Fermentation

Cheng, Chi, Cheng
http://rave.ohiolink.edu/etdc/view?acc_num=osu1511827507089631

Abstract Details

2017, Doctor of Philosophy, Ohio State University, Chemical Engineering.
Excessive CO2 emission is a major environmental concern because it can cause significant climate change. Since CO2 is thermodynamically stable, CO2 capture and utilization via chemical routes are not effective. On the other hand, CO2 fixation by microorganisms can provide a novel and economical way to turn CO2 into industrial products. This study focused on CO2 utilization by using microorganisms via pyruvate carboxylase (PyrC) for poly(L-malic acid) (PMA) and malic acid (MA) production, and via the Wood-Ljungdahl pathway for ethanol and butanol production. CO2 can be incorporated into pyruvate to form oxaloacetate (OAA) by PyrC in A. pullulans, and OAA can then be converted to MA and PMA via the reductive tricarboxylic acid (rTCA) pathway. PMA is a biodegradable, water soluble and biocompatible polymer, and has huge potential applications in the biopharmaceutical industry. In addition, PMA can be readily hydrolyzed to MA, which is widely used as an acidulant in foods and pharmaceuticals. A. pullulans ZX-10, a black yeast, can utilize all sugars in soybean hull hydrolysate and soy molasses. With CO2 (in the form of CaCO3 ) supplementation, fermentation from soybean hull hydrolysate gave a malic acid yield of ~0.4 g/g sugars consume with a productivity of ~0.5 g/L·h, and fermentation from soy molasses gave a high titer (71.9 g/L) and yield (0.69 g/g) in fed-batch reactor and a high productivity of 0.64 g/L·h in repeated batch fermentation with cell recycle. Cost analysis was performed for a 5000-metric-ton plant with soy molasses, soybean hull, and corn as substrate. The calculated unit production cost of MA was $1.10/kg from soy molasses, $1.74/kg from soybean hull, and $1.37/kg from corn, compared to the market price of $1.75/kg. These results show that MA production from soy molasses via PMA fermentation by A. pullulans offers a cost-competitive process for industrial application. Sugarcane juice is a relatively cheap and abundant biomass and can readily be used for PMA and MA production without any pretreatment. PMA and MA production from sugarcane juice and CO2 by A. pullulans gave a high PMA titer of 116.3 g/L and yield of 0.41 g/g in fed-batch fermentation, and a high productivity of 0.66 g/L·h in repeated-batch fermentation with cell recycle. A process economic analysis for a 2500metric-ton plant showed that PMA could be produced from sugarcane juice at $1.33/kg, offering an economically competitive process for production of bio-based PMA for industrial applications. The Wood-Ljungdahl (W-L) pathway is the most energy-efficient autotrophic CO2 fixation pathway. Several acetogens, including Acetobacterium woodii, Clostridium aceticum and Clostridium carboxidivorans can use syngas (CO2 , CO, and H2 ) for growth with acetate as the main end product. Some of them can also produce ethanol and butanol, in addition to acetate. C. aceticum was engineered to overexpress adhE2 (encoding a bifunctional alcohol/aldehyde dehydrogenase) and fnr (encoding a ferredoxin:NADH oxidoreductase) for ethanol production. However, the engineered C. aceticum was not able to produce ethanol from CO2 , probably because four pHdependent native aldehyde:ferredoxin oxidoreductases favored oxidative reaction at the fermentation pH of ~8.2, even though in vitro enzyme assays showed ethanol dehydrogenase and acetaldehyde dehydrogenase activities. C. carboxidivorans naturally can produce acetate, butyrate, ethanol, and butanol from glucose and CO2 /H2 . C. carboxidivorans wild-type (WT) produced 2.00 g/L ethanol and 0.297 g/L butanol from syngas (CO2 :CO:H2 [20:40:40], total pressure 1 atm) in serum bottles. C. carboxidivorans was engineered to overexpress different alcohol production genes (adhE2, aor, adhE2-fnr, and aor-fnr, respectively) and their effects on alcohol production were investigated. Compared to the C. carboxidivorans wild-type strain, C. carboxidivorans mutant overexpressing adhE2 produced ~50% more ethanol, and mutant overexpressing adhE2 and fnr produced ~18% more butanol and ~22% more ethanol, while mutant overexpressing aor produced a similar amount of alcohols compared to wild-type. These results showed that the overexpression of adhE2 could effectively increase alcohol production in C. carboxidivorans, and syngas can be used as a cheap feedstock for efficient ethanol and butanol production from CO2 .
Shang-Tian Yang (Advisor)
182 p.
Chemical Engineering

Recommended Citations

Citations

  • Cheng, Cheng, C. (2017). Chemicals and Biofuels Production from CO2 and Biomass by Fermentation [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1511827507089631

    APA Style (7th edition)

  • Cheng, Cheng, Chi. Chemicals and Biofuels Production from CO2 and Biomass by Fermentation. 2017. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1511827507089631.

    MLA Style (8th edition)

  • Cheng, Cheng, Chi. "Chemicals and Biofuels Production from CO2 and Biomass by Fermentation." Doctoral dissertation, Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1511827507089631

    Chicago Manual of Style (17th edition)

osu1511827507089631
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© 2017, some rights reserved.Creative Commons License Chemicals and Biofuels Production from CO2 and Biomass by Fermentation by Chi Cheng Cheng is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License. Based on a work at etd.ohiolink.edu.
This open access ETD is published by The Ohio State University and OhioLINK.