Inducing Expression and Reaction Characteristic of Nitrile Hydratase from Rhodococcus sp. SHZ-11

Inducing expression and the reaction characteristic of nitrile hydratase (NHase) from Rhodococcus sp. SHZ-1 were investigated. The results showed that the expression of NHase was greatly enhanced with the cooperation of acrylonitrile and ammonium chloride as inducer in the medium and the specific activity of NHase was increased of 44%. Then the temperature, pH, concentration of acrylonitrile and acrylamide were evaluated, which affected the activity and reaction characteristic of NHase. It was found that the temperature and concentration of acrylamide were the most important factors for the catalyzation of NHase. The optimal catalysis temperature of NHase from Rhodococcus sp. SHZ-1 was 30°C, and the activation energy of the hydration of NHase was 90.2kJ·mol−1 in the temperature range from 5°C to 30°C. Km of NHase was 0.095mol·L−1 using acrylonitrile (AN) as substrate, and NHase activity was inhibited seriously when acrylonitrile concentration was up to 40g·L−1, the substrate inhibition constant Ki is 0.283mol·L−1. Moreover, the NHase from Rhodococcus sp. SHZ-1 had very strong tolerance to acrylamide, in which the final concentration of acrylamide reached to 642g·L−1 and the residual activity of NHase still maintained 8.6% of the initial enzyme activity.