Cysteine synthase A overexpression in Corynebacterium glutamicum enhances l ‐isoleucine production

Cysteine synthase A (CysK) catalyzes the last reaction of l ‐cysteine synthesis in bacteria, but its moonlighting functions have been revealed recently. In this study, CysK was overexpressed in Corynebacterium glutamicum IWJ001, an l ‐isoleucine producer. Compared with the control IWJ001/pDXW‐8, IWJ001/pDXW‐8‐ cysK cells grew fast during log phase, and produced 26.5% more l ‐isoleucine in flask fermentation and 23.5% more l ‐isoleucine in fed‐batch fermentation. The key genes aspC , lysC , hom , thrB , ilvA , and ilvBN involved in l ‐isoleucine biosynthesis were all upregulated in IWJ001/pDXW‐8‐ cysK , compared with IWJ001/pDXW‐8. In addition, IWJ001/pDXW‐8‐ cysK cells were longer and thicker than IWJ001/pDXW‐8 cells. Compared with IWJ001/pDXW‐8, the membrane permeability increased 15.8% and biofilm formation ability decreased 71.3% for IWJ001/pDXW‐8‐ cysK cells. The results demonstrate that CysK overexpression in C. glutamicum is a good approach to enhance l ‐isoleucine production.