[Catalytic and Stereoselective Properties of the Immobilized Amidase of Rhodococcus rhodochrous 4-1].

The amidase of Rhodococcus rhodochrous 4-1 was immobilized by covalent attachment to activated chitosan by physical sorption on carbon adsorbents and by the formation of crosslinked aggregates in the absence of carrier material. Comparative analysis of particular catalytic properties of the free and chitosan-immobilized amidase was performed. It was shown that the enzyme retained 50-60% of its initial activity after covalent immobilization on chitosan and was characterized by increased temperature stability as compared to soluble amidase. Moreover, the immobilized enzyme retained more than 20% of its activity after five 24-h cycles of acrylamide deamination. The effects of different types of immobilization on amidase stereose-lective properties were studied by the model reaction of racemic lactamide hydrolysis to D-lactic acid and L-lactic acid. It was shown that crosslinked amidase aggregates possessed high D-stereoselectivity (up to 77-94%). The immobilized enzyme showed the highest enantioselectivity at 60 degrees C.