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℃

the total deactivation rate constant was about 2.8-fold of that at 20℃.