Enhancing the production of γ-aminobutyric acid in Escherichia coli BL21 by engineering the enzymes of the regeneration pathway of the coenzyme factor pyridoxal 5'-phosphate

The compound γ-aminobutyric acid (GABA) was widely used in various fields. To enhance the production of GABA in Escherichia coli BL21(DE3), the enzymes of the regeneration pathway of the coenzyme factor pyridoxal 5'-phosphate (PLP) were engineered. The recombinant E. coli strain was screened and identified. The initial concentrations of L-monosodium glutamate (L-MSG) had an obvious influence on the production of GABA. The highest concentration of GABA in recombinant E. coli BL21/pET28a-gadA was 5.54 g/L when the initial L-MSG concentration was 10 g/L, whereas it was 8.45 g/L in recombinant E. coli BL21/pET28a-gadA-SNO1-SNZ1 at an initial L-MSG concentration of 15 g/L. The corresponding conversion yields of GABA in these two strains were 91.0% and 92.7%, respectively. When the initial concentrations of L-MSG were more than 15 g/L, the concentrations of GABA in E. coli BL21/pET28a-gadA-SNO1-SNZ1 were significantly higher as compared to those in recombinant E. coli BL21/pET28a-gadA, and it reached a maximum of 13.20 g/L at an initial L-MSG concentration of 25 g/L, demonstrating that the introduction of the enzymes of the regeneration pathway of PLP favored to enhance the production of GABA. This study provides new insight into producing GABA effectively in E. coli BL21(DE3).