The Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, JiangNan University, 1800# Lihu Road, Wuxi, 214122, JiangSu Province, People's Republic of China.
J Ind Microbiol Biotechnol. 2012 Jan;39(1):63-72. doi: 10.1007/s10295-011-1000-1. Epub 2011 Jun 25.
Brevibacterium flavum ATCC14067 was engineered for L: -valine production by overexpression of different ilv genes; the ilvEBN(r)C genes from B. flavum NV128 provided the best candidate for L: -valine production. In traditional fermentation, L: -valine production reached 30.08 ± 0.92 g/L at 31°C in 72 h with a low conversion efficiency of 0.129 g/g. To further improve the L: -valine production and conversion efficiency based on the optimum temperatures of L: -valine biosynthesis enzymes (above 35°C) and the thermotolerance of B. flavum, the fermentation temperature was increased to 34, 37, and 40°C. As a result, higher metabolic rate and L: -valine biosynthesis enzymes activity were obtained at high temperature, and the maximum L: -valine production, conversion efficiency, and specific L: -valine production rate reached 38.08 ± 1.32 g/L, 0.241 g/g, and 0.133 g g(-1) h(-1), respectively, at 37°C in 48 h fermentation. The strategy for enhancing L: -valine production by overexpression of key enzymes in thermotolerant strains may provide an alternative approach to enhance branched-chain amino acids production with other strains.
黄色短杆菌 ATCC14067 经工程改造后，通过过度表达不同的 ilv 基因来生产 L: -缬氨酸；黄色短杆菌 NV128 的 ilvEBN(r)C 基因是生产 L: -缬氨酸的最佳候选基因。在传统发酵中，L: -缬氨酸的生产在 31°C 下 72 小时达到 30.08 ± 0.92 g/L，转化率低至 0.129 g/g。为了进一步提高 L: -缬氨酸的生产和转化率，基于 L: -缬氨酸生物合成酶的最适温度（高于 35°C）和黄色短杆菌的耐热性，发酵温度提高到 34、37 和 40°C。结果，在高温下获得了更高的代谢率和 L: -缬氨酸生物合成酶活性，在 37°C 下发酵 48 小时，最大 L: -缬氨酸产量、转化率和比生产速率分别达到 38.08 ± 1.32 g/L、0.241 g/g 和 0.133 g g(-1) h(-1)。在耐热菌株中过度表达关键酶以提高 L: -缬氨酸产量的策略可能为提高其他菌株支链氨基酸产量提供一种替代方法。
