Abstract: A nicotinic acid hydroxylase- producing strain from spoiled fish from Bohai Bay in Yantai, designated H9, was rapidly and directionally screened using a 96-well microplate and ultraviolet imaging. Strain H9 was identified as Pseudomonas putida based on its morphological, physiological and biochemical characteristics, and 16S rDNA sequence. Our results showed that the highest activity of nicotinic acid hydroxylase of 0.37 U/mL was obtained by culturing strain H9 with 50 mL of a medium consisting of 15 g/L soluble starch, 15 g/L corn steep liquor, 10 g/L nicotinic acid and, 1.0 g/L K2HPO4 at an initial pH of 7.0 in a 500-mL flask at 25 ℃ with an inoculum amount of 7%, which was increased by 68% as compared to that before optimization. The yield of 6-hydroxynicotinic acid (6-HNA) produced by resting cell biotransformation reached 124.77 g/L. Accordingly, strain H9 had a promising application potential in the industrial production of 6-hydroxynicotinic acid.

Key words: nicotinic acid, 6-hydroxynicotinic acid, Pseudomonas putida, nicotinic acid hydroxylase, optimization of culture conditions