Deactivation Kinetics of Nitrile Hydratase in Free Resting Cells

Nitrile hydratase (NHase) is an important industrial enzyme used for acrylamide production from acrylonitrile. The deactivation kinetics of NHases in free resting cells of Rhodococcus sp. was presented based on a bi-steady state assumption. Effects of hydration temperature, product concentration and substrate concentration on NHase deactivation were investigated experimentally and correlated with a first order deactivation kinetics. The results showed that the hydration temperature and product concentration were major factors governing the deactivation of NHases under substrate-feeding conditions. When acrylamide concentration was higher than 250 g·L−1, the deactivation of NHases became serious and the bi-steady state assumption was not applicable. When the hydration temperature was controlled at a relatively higher level such as 28°C, the total deactivation rate constant was about 2.8-fold of that at 20°C.