Metabolic Engineering of <i>Corynebacterium glutamicum</i> for the High-Level Production of <scp>l</scp>-Valine under Aerobic Conditions
F Wang, Ningyun Cai, Yanlin Leng, Chen Wu, Yanan Wang, Siyu Tian, Chenglin Zhang, Qingyang Xu, Huadong Peng, Ning Chen, Yanjun Li
Abstract
l -Valine, an essential amino acid, serves as a valuable compound in various industries. However, engineering strains with both high yield and purity are yet to be delivered for microbial l -valine production. We engineered a Corynebacterium glutamicum strain capable of highly efficient production of l -valine. We initially introduced an acetohydroxy acid synthase mutant from an industrial l -valine producer and optimized a cofactor-balanced pathway, followed by the activation of the nonphosphoenolpyruvate-dependent carbohydrate phosphotransferase system and the introduction of an exogenous Entner–Doudoroff pathway. Subsequently, we weakened anaplerotic pathways, and attenuated the tricarboxylic acid cycle via start codon substitution in icd, encoding isocitrate dehydrogenase. Finally, to balance bacterial growth and l -valine production, an l -valine biosensor-dependent genetic circuit was established to dynamically repress citrate synthase expression. The engineered strain Val19 produced 103 g/L of l -valine with a high yield of 0.35 g/g glucose and a productivity of 2.67 g/L/h. This represents the highest reported l -valine production in C. glutamicum via direct fermentation and exhibits potential for its industrial-scale production, leveraging the advantages of C. glutamicum over other microbes.