Preparation of (R)-(−)-mandelic acid and its derivatives from racemates by enantioselective degradation with a newly isolated bacterial strain Alcaligenes sp. ECU0401

Abstract

An enantioselective mandelate-degrading bacterium, Alcaligenes sp. ECU0401, was newly isolated from soil. By fed-batch culture, (R)-(-)-mandelic acid was successfully prepared in a 5-L fermenter with 32.8% isolated yield and >99.9% enantiomeric excesses (e.e.) from totally 3.04% (w/v) of racemic mandelic acid after 99 h of biotransformation. The optimal reaction pH and temperature were 6.5 and 30 degrees C, respectively. Using the resting cell as a biocatalyst for asymmetric degradation of racemic mandelic acid and chloro-substituted derivatives thereof, (R)-(-)-mandelic acid, (R)-(-)-o-chloromandelic acid, (S)-(+)-m-chloromandelic acid and (S)-(+)-p-chloromandelic acid were recovered with high analytic yields and excellent enantiomeric excesses (e.e. > 99.9%). (R)-(-)-Mandelic acid could also be obtained after 12 h of biotransformation with 41.5% isolated yield and >99.9% e.e.