文摘
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 ¡ãC, 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.