Crucial factors affecting the nitrile hydratase production of Mesorhizobium sp. F28

Mesorhizobium sp. F28 contains cobalt-NHase, which effectively converts acrylonitrile into acrylamide. When urea was added to the culture medium, the NHase activity was 62.3 U ml−1 (R2A-R2A/urea) after 22.5 h of cultivation, which was similar to that in the medium without addition (R2A-R2A, 70.0 U ml−1). The relative activity of the purified NHase was 100%, 92%, 94%, and 92% in the medium containing, respectively, 0 mM, 2 mM, 5 mM, and 10 mM of urea. Urea had no significant effect on the purified NHase activity of Mesorhizobium sp. F28. This research did not observe the NHase production by Mesorhizobium sp. F28 when acrylonitrile was supplemented in the culture medium except that cobalt ions existed. The highest enzyme activity was 328.5 U ml−1 as cobalt ions were added in the pre-culture and culture medium after 22.5 h of cultivation (R2A/Co-R2A/Co); compared to media without cobalt ions (R2A-R2A, 22.5 h, 70.5 U ml−1) this is an almost five-fold enhancement. It can be concluded that culture media containing cobalt ions was beneficial for the formation of active NHase of Mesorhizobium sp. F28.