Enhanced L‐serine production by Corynebacterium glutamicum based on novel insights into L‐serine exporters

Abstract The L‐serine exporters ThrE and SerE play important roles in L‐serine production by Corynebacterium glutamicum. Deletion of both thrE and serE decreased L‐serine titer by 60%, suggesting the existence of other L‐serine exporters. A comparative transcriptomics identified NCgl0254 and NCgl0255 as novel L‐serine exporters. Further analysis of the contributions of ThrE, SerE, NCgl0254, and NCgl0255 found that SerE was the major L‐serine exporter in C. glutamicum and these four L‐serine exporters were responsible for 79.7% of L‐serine export. Deletion of one L‐serine exporter upregulated the transcription levels of the other three, which might be coursed by increased intracellular concentrations of L‐serine. Overexpression of NCgl0254 and NCgl0255 increased L‐serine titer by 20.8% in C. glutamicum A36, while overexpression of the four L‐serine exporters increased L‐serine production by 31.9% (41.1 g·L−1) in C. glutamicum A36. The identification of novel L‐serine exporters in C. glutamicum will help to improve industrial production of L‐serine.