Modifying Corynebacterium glutamicum by metabolic engineering for efficient synthesis of l-lysine

This study described that a low-producing mutagenic strain was transformed to a l-lysine high-producing recombinant strain by optimizing the l-lysine metabolic pathway of Corynebacterium glutamicum. The nucleotide sequence results revealed that the lysC of mutant strain CgK37 mutated at 279th codon. Based on this site, site-directed saturation mutation was performed to screen for the mutant with better effect in relieving aspartate kinase feedback inhibition. Then, the supply of oxaloacetate and nicotinamide adenine dinucleotide phosphate was increased via knockout and overexpression of related genes. In order to solve the problem of low utilization efficiency of culture medium, fructokinase gene gmuE was heterologous expressed in CgK37, which could directly use intracellular fructose to improve the growth rate. In addition, the synthesis of partial by-products was weakened at the gene transcription level to avoid carbon excessively flowing into the branch metabolism. Finally, a large-scale fermentation experiment was conducted in 5 L jar fermenter. The l-lysine yield of CgK37-11 was 196.58 ± 1.68 g/L, which was 83.24% original higher than CgK37, and the productivity reached 2.46 g/L/h.