A new thermostable nitrilase-producing isolate identified as Streptomyces sp. MTCC 7546 has been studied extensively for the optimization of enzyme production operating in batch mode. The benzonitrile was observed as inducer of nitrilase production. The isolate showed maximum nitrilase production after 24h of incubation at optimal conditions. The strain grows well on a variety of carbon sources and produces the nitrilase that catalyses the hydrolysis of nitriles to acids without formation of amides. The enzyme is mostly active against mono- and di-aliphatic nitriles (10 mmol L-1) at pH of 7.4 and at a temperature of 50 degrees C. (c) 2007 Society of Chemical Industry.