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Process Development and Metabolic Engineering for Enhanced Propionic Acid Production by Propionibacterium freudenreichii subsp. shermanii

Wang, Zhongqiang
http://rave.ohiolink.edu/etdc/view?acc_num=osu1374189444

Abstract Details

2013, Doctor of Philosophy, Ohio State University, Biochemistry Program, Ohio State.
Propionic acid is an important C3 carboxylic acid with wide applications. The majority of propionic acid, in the form of ammonium, sodium and potassium salts, is used as preservatives for animal feed, grains, dairy and bakery products due to its antifungal properties. Propionic acid and its derivatives are also used for the manufacture of many chemical products, such as cellulose fibers, perfumes, pharmaceuticals, herbicides and solvents. The market and price of propionic acid are steadily increasing. Currently, propionic acid is produced exclusively via petrochemical processes, especially from ethylene, carbon monoxide and steam. Due to the concerns over the sustainability of crude oil supply and the environmental pressure caused by the petrochemical industry, there is increasing interests on propionic acid synthesis from alternative pathways. Fermentative propionic acid production from renewable biomass has been shown to be a sustainable and promising alternative. Because it is mainly used for consumer commodities, bio-based propionic acid is preferred by the public. However, since propionic acid has strong inhibition effects on microorganisms, its fermentation suffers from low yield, productivity, titer and purity. This work was aimed to improve the economic feasibility and efficiency of propionic acid fermentation by process development and metabolic engineering. Propionibacterium freudenreichii subsp. shermanii has been studied extensively for propionic acid fermentation and the genetic engineering of propionibacteria because of its publically available genome sequence and high transformation efficiency. Glucose fermentation yields acetic acid as the major byproduct for redox balance purpose. Glycerol has a higher reductance degree than glucose, so it is favored for the production of reductive products. The reductance degree of carbon source determines the carbon flux distribution in propionic acid fermentation, as a result of NADH/NAD+ balance. Although glycerol fermentation has diminished acetic acid formation and possesses a significantly higher propionic acid yield (0.39 vs. 0.65 g/g), its productivity is impaired as the expense. In this study, the co-fermentation of glucose and glycerol was performed at different glycerol/ glucose mass ratios in serum bottles and bioreactors. A high propionic acid yield (0.54-0.65 g/g), productivity (0.18-0.23 g/Lh) and selectivity (P/A: ~14; P/S: ~10) could be obtained at an appropriate ratio. Renewable feedstocks, such as crude glycerol, cassava bagasse hydrolysate and corn steep liquor, were used in co-fermentation without any inhibition effects. A fibrous bed bioreactor (FBB) system was used for the co-fermentation to establish an efficient propionic acid production process from cheap biomass wastes. Although the genetic engineering of P. shermanii was reported before, no work has been done on the metabolic engineering. This was the first study to modify the metabolic pathways of P. shermanii for enhanced propionic acid production. Carbon flux distribution analysis was carried out for all strains to investigate the flux redistribution caused by enzyme overexpression. This study demonstrated that propionic acid could be produced by P. shermanii at a relatively high yield and productivity from renewable feedstocks. Several metabolically engineered strains of P. shermanii have been constructed. An economic and efficient propionic acid production process could be established by employing suitable substrates and mutant strains.
Shang-Tian Yang (Advisor)
Jeffrey Chalmers (Committee Member)
Earl Harrison (Committee Member)
264 p.
Biochemistry; Chemical Engineering

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Citations

  • Wang, Z. (2013). Process Development and Metabolic Engineering for Enhanced Propionic Acid Production by Propionibacterium freudenreichii subsp. shermanii [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1374189444

    APA Style (7th edition)

  • Wang, Zhongqiang. Process Development and Metabolic Engineering for Enhanced Propionic Acid Production by Propionibacterium freudenreichii subsp. shermanii. 2013. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1374189444.

    MLA Style (8th edition)

  • Wang, Zhongqiang. "Process Development and Metabolic Engineering for Enhanced Propionic Acid Production by Propionibacterium freudenreichii subsp. shermanii." Doctoral dissertation, Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1374189444

    Chicago Manual of Style (17th edition)

osu1374189444
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© 2013, all rights reserved.
This open access ETD is published by The Ohio State University and OhioLINK.