Metabolic engineering of glucose uptake systems in Corynebacterium glutamicum for improving the efficiency of...

Traditional amino acid producers typically exhibit the low glucose uptake rate and growth deficiency, resulting in a long fermentation time because of the accumulation of side mutations in breeding of strains. In this study, we demonstrate that the efficiency of L-lysine production in traditional L-lysine producer Corynebacterium glutamicum ZL-9 can be improved by rationally engineering glucose uptake systems. To do this, different bypasses for glucose uptake were investigated to reveal the best glucose uptake system for L-lysine production in traditional L-lysine producer. This study showed that overexpression of the key genes in PTS^Glc or non-PTS^Glc increased the glucose consumption, growth rate, and L-lysine production. However, increasing the function of PTS^Glc in glucose uptake led to the increase of by-products, especially for plasmid-mediated expression system. Increasing the participation of non-PTS^Glc in glucose utilization showed the best glucose uptake system for L-lysine production. The final strain ZL-92 with increasing the expression level of iolT1, iolT2 and ppgK could produce 201.6 ± 13.8 g/L of L-lysine with a productivity of 5.04 g/L/h and carbon yield of 0.65 g/(g glucose) in fed-batch culture. This is the first report of a rational modification of glucose uptake systems that improve the efficiency of L-lysine production through increasing the participation of non-PTS^Glc in glucose utilization in traditional L-lysine producer. Similar strategies can be also used for producing other amino acids or their derivatives.