Enantioselective hydrolysis of O-acetylmandelonitrile to O-acetylmandelic acid by bacterial nitrilases

Bacteria were enriched from soil samples, using benzylcyanide, -methyl-, -ethyl- or -methoxybenzyl-cyanide as the sole source of nitrogen. All isolated strains belonged to the genus Pseudomonas. Resting cells of the isolates hydrolysed O-acetylmandelonitrile to O-acetylmandelic acid, O-acetylmandelic acid amide and mandelic acid. From racemic O-acetylmandelonitrile all isolates preferentially formed R(–)-acetylmandelic acid ( = d-acetylmandelic acid). The enantioselective hydrolysis of O-acetylmandelonitrile could also be demonstrated in vitro. Crude extracts did not hydrolyse O-acetylmandelic acid amide indicating an enantioselective nitrilase rather than a nitrile hydratase/amidase system.