Improving stability and reusability of Rhodococcus pyridinivorans NIT-36 nitrilase by whole cell immobilization using chitosan

Immobilized enzymes have great significance for industrial processes. In this study whole cell immobilization of Rhodococcus pyridinivorans NIT-36 has been undertaken using chitosan microspheres as an immobilized matrix. R. pyridinivorans NIT-36 harbors a significant intracellular enzyme nitrilase. Chitosan microspheres were generated by supplementing chitosan with glutaraldehyde and results, supported the porous microsphere structure via SEM. The resultant microspheres exhibited cell immobilization capacity of 450 mg/g. The immobilized cells exhibited a considerable increase in temperature tolerance at 60 °C as compared to free cells. The immobilized microspheres also demonstrated higher substrate tolerance. The immobilized nitrilase retained 80% activity when stored at 4 °C for 10 days and retained 50% activity after 7 reuse cycles. It may be concluded that chitosan microspheres are a novel immobilization agent for whole cell immobilization which enhances the stability and reusability of nitrilase enzyme.