Stereoselective hydration of (RS)-phenylglycine nitrile by new whole cell biocatalysts

Abstract Five new bacterial isolates with stereoselective nitrile hydratase activity against ( RS )-2-phenylpropionitrile and ( RS )-phenylglycine nitrile were investigated. The permeabilized whole cell isolates selectively hydrate the ( S )-enantiomer of phenylglycine nitrile with E values of 1.2–5.4. One isolate, which was identified as Pantoea endophytica , produced pure ( S )-phenylglycine (>99% ee ) as a result of hydrolysis of ( S )-phenylglycine amide by an ( S )-specific amidase. Surprisingly, in the hydrolysis of ( RS )-phenylglycine nitrile, it was found that the ( R )-amide was accumulated in excess (21% ee ) despite the nitrile hydratase produced by Pantoea endophytica was ( S )-selective. The synthesis of pure ( R ) - phenylglycine (>99% ee ) was achieved in time course studies using another Pantoea sp. with ( R )-selective amidase. In the case of Nocardioides sp. the intermediate product, ( S )-phenylglycine amide, could be produced (52% ee ) without its subsequent hydrolysis into the acid due to the apparent absence of any amidase activity.