Abstract: L-cysteine is an important sulfur-containing amino acid, which is widely used in pharmaceutical, food and cosmetic industries. In this study, C. glutamicum A36 was engineered to efficiently produce L-cysteine from sugar, and showed highest L-serine titer comparing with its' parent strain. In order to produce L-cysteine, two types of the serine O-acetyltransferase (gene encoded by cysE) were overexpressed in strain A36 respectively, strain S-C-1 and S-C-2 had been constructed, L-cysteine titer was 115.8 mg/L and 105.8 mg/L, respectively, and the parent strain A36 couldn't produce L-cysteine. Subsequently, in order to increase the titer of L-cysteine, several metabolic engineering strategies were performed, including overexpression of the OASS-A (gene encoded by cysK) and the L-cysteine exporter Bcr (gene encoded by bcr), and the deletion of the degradation pathway. A series recombinant strain had been constructed, and among all strains, S-C-7 showed the highest L-cysteine titer of 286.7 mg/L. The sulfur source was optimized to increase L-cysteine titer further, the addition of 12 g/L sodium thiosulfate at 24 h showed the highest L-cysteine titer of 581.6 mg/L, which was two times of that before optimization. Finally, in 5 L fermenter, the L-cysteine titer of strain S-C-7 could reach 1.2 g/L, which was the highest titer of L-cysteine produced by C. glutamicum up to now. It laid a foundation for the L-cysteine production by C. glutamicum.
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2022, Vol. 48 
