Abstract: The strain of Rhodococcus rhodochrous tg1-A6 with high activity of nitrilase was used to convert 3-cyanopyridine to nicotinic acid.By using resting cells,the optimum substrate concentration was 130 mmol/L,and the optimized temperature and pH were 55℃ and 7.0,respectively.Under the optimal conditions,100% of the added 3-cyanopyridine could be converted,and the highest concentration of nicotinic acid in reaction mixture achieved 165.2 g/L at 15 h.In case of higher yield,the resting cells could be reused for seven batches catalyzing(total 67 h),and the summed yield of nicotinic acid could reach 529 g/L.