Synthesis of enantiomerically pure (S)-mandelic acid using an oxynitrilase-nitrilase bienzymatic cascade:: a nitrilase surprisingly shows nitrile hydratase activity

Benzaldehyde was converted into enantiomerically pure (S)-mandelic acid by sequential HCN addition and hydrolysis in the presence of a cross-linked enzyme aggregate composed of the (S)-selective oxynitrilase from Manihot esculenta and the non-selective recombinant nitrilase from Pseudomonas fluorescens EBC 191. Surprisingly, (S)-mandelic amide was formed in large amounts. It was shown, in separate experiments, that the nitrilase hydrolyses (S)-mandelonitrile into an approx. equimolar mixture of acid and amide, whereas with the (R)-enantiomer only 10% of amide was formed. (c) 2006 Elsevier Ltd. All rights reserved.