Nitrile-metabolizing potential of Amycolatopsis sp. IITR215

Strain Amycolatopsis sp. IITR215 was isolated from a sewage sample using polyacrylonitrile powder as the sole nitrogen source. Identification was performed by 16S rDNA analysis. The isolated strain harbored multiple nitrile-metabolizing enzymes having a wide range of substrate specificities. It metabolized nitrile and amide compounds with constitutive enzymes. Studies using an amidase inhibitor showed that hydrolysis of acrylonitrile and acrylamide occurred due to nitrile hydratase and amidase, respectively, while hydrolysis of hexanenitrile was due to the action of either nitrilase or a second nitrile hydratase/amidase system. The inhibitory effects of N-bromosuccinimide and N-ethylmaleimide on enzymes of this culture were also studied and this further indicated the involvement of either a nitrilase or a second nitrile hydratase/amidase system for hydrolysis of hexanenitrile. Interestingly, hexanenitrile hydrolysis exhibited an optimum temperature of 55 °C, whereas acrylonitrile and acrylamide hydrolysis showed an optimum temperature of 45 °C. The optimum pH was 5.8 for hexanenitrile hydrolysis and 7.0 for acrylonitrile and acrylamide hydrolysis. Hexanenitrile hydrolysis by enzymes of this strain showed better organic solvent tolerance in the presence of alcohols. The maximum enzyme activity of nitrile-metabolizing enzymes was found using media containing isobutyramide as the nitrogen source. This is the first report on constitutive multiple enzymes from the Amycolatopsis genus.