Abstract Aspergillus sp. PTCC 5266 exhibited nitrile-hydrating activity over a broad pH range from 6.0 to 10.0 at 26° C. It hydrated 4-nitrophenylacetonitrile, 2-chlorobenzonitrile and 3-chlorobenzonitrile to their corresponding carboxylic acids and amides, while benzyl cyanide, benzonitrile, 4-tolunitrile, cyclohexanecarbonitrile, 4-chlorobutyronitrile and isobutyronitrile gave carboxylic acids as the sole products. The maximum whole-cell nitrile ...