Wang Guanglu, Bai Ling, Wang Zhiwen, Shi Ting, Chen Tao, Zhao Xueming
Department of Biochemical Engineering, School of Chemical Engineering and Technology, Tianjin University, 92# Weijin Road, Nankai District, Tianjin, 300072, People's Republic of China.
World J Microbiol Biotechnol. 2014 Jun;30(6):1893-900. doi: 10.1007/s11274-014-1611-6. Epub 2014 Jan 30.
The regulation of metabolic flux through glycolytic versus the gluconeogenic pathway plays an important role in central carbon metabolism. In this study, we made an attempt to enhance riboflavin production by deregulating gluconeogenesis in Bacillus subtilis. To this end, gapB (code for NADPH-dependent glyceraldehyde-3-phosphate dehydrogenase), fbp (code for fructose-1,6-bisphosphatase) and pckA (code for phosphoenolpyruvate carboxykinase) were overexpressed in parental strain B. subtilis RH33. Compared with RH33, overexpression of fbp and gapB resulted in approximately 18.0 and 14.2 % increased riboflavin production, respectively, while overexpression of pckA obtained the opposite result. Significant enhancement of riboflavin titers up to 4.89 g/l was obtained in shake flask cultures when gapB and fbp were co-overexpressed, nevertheless the specific growth rate decreased slightly and the specific glucose uptake rate remained almost unchanged. An improvement by 21.9 and 27.8 % of the riboflavin production was achieved by co-overexpression of gapB and fbp in shake flask and fed-batch fermentation, respectively. These results imply that deregulation of gluconeogenesis is an effective strategy for production of metabolites directly stemming from the pentose phosphate pathway as well as other NADPH-demanding compounds with glucose as carbon source in B. subtilis.
通过糖酵解途径与糖异生途径对代谢通量的调控在中心碳代谢中起着重要作用。在本研究中，我们试图通过解除枯草芽孢杆菌中糖异生的调控来提高核黄素的产量。为此，在亲本菌株枯草芽孢杆菌RH33中过表达了gapB（编码NADPH依赖性甘油醛-3-磷酸脱氢酶）、fbp（编码果糖-1,6-二磷酸酶）和pckA（编码磷酸烯醇式丙酮酸羧激酶）。与RH33相比，fbp和gapB的过表达分别使核黄素产量提高了约18.0%和14.2%，而pckA的过表达则得到相反的结果。当gapB和fbp共过表达时，摇瓶培养中核黄素滴度显著提高至4.89 g/l，不过比生长速率略有下降，比葡萄糖摄取速率几乎保持不变。在摇瓶培养和分批补料发酵中，gapB和fbp共过表达分别使核黄素产量提高了21.9%和27.8%。这些结果表明，在枯草芽孢杆菌中，解除糖异生的调控是一种有效的策略，可用于生产直接源自磷酸戊糖途径的代谢产物以及其他以葡萄糖为碳源的需要NADPH的化合物。
