全局调控因子Lrp的表达强化谷氨酸棒状杆菌发酵生产L-缬氨酸

作者研究发现全局调控因子Lrp的表达能促进谷氨酸棒状杆菌发酵生产L-缬氨酸，但对菌体生长有一定影响。RT-PCR分析发现：Lrp的表达能提高L-缬氨酸合成相关基因ilvA、ilvBN、ilvC、ilvD及转运相关基因brnFE的转录水平，这也许是L-缬氨酸产量提高的原因。实验还发现：表达含有点突变（Arg39Trp）的Lrp可以进一步提高谷氨酸棒状杆菌L-缬氨酸的产量，而且对菌体生长的影响也减小；这种效果在lrp-brnF间隔区域存在突变的L-缬氨酸生产菌VWB-1中更加明显。在VWB-1中共表达lrp1和brnFE基因，5 L罐发酵L-缬氨酸产量达到42.1 g/L，比对照提高了48.9%。
L-valine is one of the branched chain amino acids widely used in food，feed，and drug industries. In this study，the global regulator Lrp was found to improve L-valine production in C. glutamicum，but slightly inhibit the growth. RT-PCR analysis showed that expression of lrp increased the transcriptional levels of genes related to L-valine biosynthesis （ilvA，ilvBN，ilvC，ilvD） and export （brnFE），which might be the reason for the improved L-valine production. A single amino acid substitution （Arg39Trp） in Lrp reduced the growth inhibition and led to higher L-valine production，especially in L-valine production strain C. glutamicum VWB-1 which contains mutations in the region between lrp and brnF. By co-expressing lrp1 and brnFE in VWB-1，L-valine production of fed-batch fermentation reached 42.1 g/L which was 48.9% increase