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| Effect of Dissolved Oxygen on γ-PGA Fermentation |
| LI Xiao-xin1, GAO Ming-hao1, ZHANG Miao-miao1, LIU Xiao-chen1, QIAO Chang-sheng1,2 |
1. Key Laboratory of Industrial Microbiology, Ministry of Education, Tianjin University of Science and Technology, Tianjin 300457, China;
2. Tianjin Peiyang Biotrans Company Limited, Tianjin 300457, China |
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Abstract Effects of different dissolved oxygen (DO) on the production rate of γ-PGA, at the 8, 32 and 56 hours were studied, using the 5L fermentor to synthesis γ-PGA with Bacillus licheniformis. Results indicated that neither high nor low DO value could efficiently accumulate γ-PGA based on the analysis of relevant data. The research also concerned about five kinds of enzyme activity which were key enzymes of metabolic flux of biosynthesis for γ-PGA. The enzymes includes hexokinase, glucose-6-phosphate dehydrogenase(G-6-Dp), pyruvate dehydrogenase(PDH), isocitrate dehydrogenase(ICDH)and glutamate dehydrogenase(GDH). And G-6-D Pcould depress the synthesis of γ-PGA. High activity of Hexokinase and GDH would promote the production of γ-PGA. PDH and ICDH might advance the production rate of cell. The higher activity of PDH and ICDH might be not conductive to the fermentation. Moreover, the extracellular metabolites profiles of fermentation under three different DO values were acquired and the metabolic flux redistribution of pathways related to γ-PGA biosynthesis was calculated based on the collected data. As a result, the metabolic flux favored to distribute toward glycolytic pathway at DO 30%, in which the ingestion rate of extracellular glutamic acid was higher and the subsequent γ-PGA biosynthesis was enhanced.
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Received: 08 October 2014
Published: 25 March 2015
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