Characterization, modification, and overexpression of 3-phosphoglycerate dehydrogenase in Corynebacterium glutamicum for enhancing l-serine production

Abstract

The direct fermentative production of l-serine from renewable biomass using Corynebacterium glutamicum is attracting increasing attention. In this study, wild-type C. glutamicum SYPS-062 produced up to 6.65 ± 0.23 g/L l-serine; to further improve l-serine production, the serA gene was cloned, and the C-terminal domain of 3-phosphoglycerate dehydrogenase (PGDH) from this strain was truncated. When expressed in Escherichia coli, the resultant mutein SerAΔ197 showed a specific PGDH activity of 1.092 ± 0.05 U/mg protein, representing a decrease of 25.87 % from that encoded by serA, and was no longer sensitive to high concentrations of l-serine. When serAΔ591 was overexpressed in C. glutamicum SYPS-062, the activity of PGDH in C. glutamicum pJC1-tac-serAΔ591 increased by 47.72 %, and the resultant strain C. glutamicum pJC1-tac-serAΔ591 could accumulate 7.69 ± 0.22 g/L l-serine. Furthermore, when serAΔ591 was overexpressed in C. glutamicum SYPS-062ΔsdaA, the resultant strain could accumulate 8.84 ± 0.23 g/L l-serine at 102 h, and the yield of l-serine on cells (Y p/x) improved by 60 % when compared with that noted in the control. These results demonstrate that l-serine production in C. glutamicum SYPS-062 could be improved by overexpressing a C-terminal truncation of PGDH in combination with other genetic modifications.