Metabolic engineering of Clostridium tyrobutyricum for enhanced butyric acid production from glucose and xylose |
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| Institution: | 1. William G. Lowrie Department of Chemical and Biomolecular Engineering, The Ohio State University, 151 West Woodruff Avenue, Columbus, Ohio 43210, USA;2. School of Life Science and Biotechnology, Dalian University of Technology, Dalian 116024, China;3. Bioprocessing Innovative Company, 4734 Bridle Path Ct., Dublin, Ohio 43017, USA;4. School of Bioscience and Bioengineering, South China University of Technology, Guangzhou 510006, China;1. Department of Chemical and Biological Engineering, The University of Alabama, 245 7th Avenue, Tuscaloosa, AL 35401, USA;2. Departments of Medicine and Biomedical Engineering, The University of Alabama at Birmingham, 703 19th Street South and 1530 3rd Avenue South, Birmingham, AL 35294, USA;3. William G Lowrie Department of Chemical and Biomolecular Engineering, The Ohio State University, 140 West 19th Avenue, Columbus, OH 43210, USA;1. National Engineering Laboratory for Cereal Fermentation Technology (NELCF), Jiangnan University, 1800 Lihu Road, Wuxi, Jiangsu 214122, China;2. The Key Laboratory of Industrial Biotechnology, Ministry of Education, Jiangnan University, 1800 Lihu Road, Wuxi, Jiangsu 214122, China;3. School of Pharmaceutical Science, Jiangnan University, 1800 Lihu Road, Wuxi, Jiangsu 214122, China;1. Renewable Product Technology Research Unit, USDA-ARS-NCAUR, Peoria, IL, USA;2. Wisconsin Institute of Sustainable Technology, University of Wisconsin, Stevens Point, USA;3. Bioenergy Research Unit, USDA-ARS-NCAUR, Peoria, IL, USA;1. School of Bioscience and Biotechnology, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600 UKM, Bangi, Selangor, Malaysia;2. Department of Chemical and Process Engineering, Faculty of Engineering, Universiti Kebangsaan Malaysia, 43600 UKM, Bangi, Selangor, Malaysia;3. Department of Applied Microbiology, Faculty of Applied Sciences, Taiz University, 6803, Taiz, Yemen;1. College of Pharmaceutical Science, Zhejiang University of Technology, Hangzhou, 310014, China;2. William G. Lowrie Department of Chemical and Biomolecular Engineering, The Ohio State University, 151 West Woodruff Avenue, Columbus, OH 43210, USA;1. Department of Biosystems Engineering, Auburn University, Auburn, AL 36849, USA;2. SFA Key Laboratory of Bamboo and Rattan Science and Technology, International Centre for Bamboo and Rattan, Beijing 100714, China;3. College of Environment and Resource, Research Center of Environment and Health, Shanxi University, Taiyuan, Shanxi 030006, China;4. College of Environmental Science and Engineering, Ocean University of China, Qingdao 266100, China;5. Department of Chemical Engineering, Auburn University, Auburn, AL 36849, USA;6. Center for Bioenergy and Bioproducts, Auburn University, Auburn, AL 36849, USA |
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| Abstract: | Clostridium tyrobutyricum is a promising microorganism for butyric acid production. However, its ability to utilize xylose, the second most abundant sugar found in lignocellulosic biomass, is severely impaired by glucose-mediated carbon catabolite repression (CCR). In this study, CCR in C. tyrobutyricum was eliminated by overexpressing three heterologous xylose catabolism genes (xylT, xylA and xlyB) cloned from C. acetobutylicum. Compared to the parental strain, the engineered strain Ct-pTBA produced more butyric acid (37.8 g/L vs. 19.4 g/L) from glucose and xylose simultaneously, at a higher xylose utilization rate (1.28 g/L·h vs. 0.16 g/L·h) and efficiency (94.3% vs. 13.8%), resulting in a higher butyrate productivity (0.53 g/L·h vs. 0.26 g/L·h) and yield (0.32 g/g vs. 0.28 g/g). When the initial total sugar concentration was ~120 g/L, both glucose and xylose utilization rates increased with increasing their respective concentration or ratio in the co-substrates but the total sugar utilization rate remained almost unchanged in the fermentation at pH 6.0. Decreasing the pH to 5.0 significantly decreased sugar utilization rates and butyrate productivity, but the effect was more pronounced for xylose than glucose. The addition of benzyl viologen (BV) as an artificial electron carrier facilitated the re-assimilation of acetate and increased butyrate production to a final titer of 46.4 g/L, yield of 0.43 g/g sugar consumed, productivity of 0.87 g/L·h, and acid purity of 98.3% in free-cell batch fermentation, which were the highest ever reported for butyric acid fermentation. The engineered strain with BV addition thus can provide an economical process for butyric acid production from lignocellulosic biomass. |
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| Keywords: | Butyric acid Carbon catabolite repression Metabolic engineering Xylose |
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