Increasing L-isoleucine production in Corynebacterium glutamicum by overexpressing global regulator Lrp and two-component export system BrnFE

Aims: To increase the L-isoleucine production in Corynebacterium glutamicum by overexpressing the global regulator Lrp and the two-component export system BrnFE. Methods and Results: The brnFE operon and the lrp gene were cloned into the shuttle vector pDXW-8 individually or in combination. The constructed plasmids were transformed into an L-isoleucine-producing strain C. glutamicum JHI3-156, and the L-isoleucine production in these different strains was analysed and compared. More L-isoleucine was produced when only Lrp was expressed than when only BrnFE was expressed. Significant increase in L-isoleucine production was observed when Lrp and BrnFE were expressed in combination. Compared to the control strain, L-isoleucine production in JHI3-156/pDXW-8-lrp-brnFE increased 63% in flask cultivation, and the specific yield of L-isoleucine increased 72% in fed-batch fermentation. Conclusions: Both Lrp and BrnFE are important to enhance the L-isoleucine production in C. glutamicum. Significance and Impact of the Study: The results provide useful information to enhance L-isoleucine or other branched-chain amino acid production in C. glutamicum.