Enhanced catalytic efficiency of nitrilase from Acidovorax facilis 72W and application in bioconversion of 3-cyanopyridine to nicotinic acid.

In this study, the catalytic efficiency using NitA from Acidovorax facilis 72W for nicotinic acid (NA) production was investigated and further improved by site-directed mutagenesis. Results showed that the specific activity of mutated NitA-C2 (F168V-S192F) towards 3-cyanopyridine increased 5-fold to 3502U02mg 611 protein. Further characterization of the biochemical properties of both nitrilases showed the optimal pH and temperature were 6.0-8.0 and 6002°C, respectively, whereas the pH and thermal stability of NitA-C2 were decreased. Finally, whole cell catalysis was adopted for NA production and a 100% conversion yield was achieved under 0.102mol02L 611 3-cyanopyridine for both strains. Besides, the conversion rate by E. coli BL21 (DE3-pET- nitA -C2) reached to 1.002mmol02min 611 02g 611 wet cell weight, which was 3-fold higher than that by E. coli BL21 (DE3-pET- nitA ). These results indicated that the mutated NitA-C2 was a promising candidate which holds potential application in biological NA production.