Effects of hydroxypropyl-β-cyclodextrin on steroids 1-en-dehydrogenation biotransformation by Arthrobacter simplex TCCC 11037

Cyclodextrins (CDs) have been shown previously to improve the steroids biotransformation. In this study, the biotransformation of cortisone acetate (CA) to prednisone acetate (PA) by Arthrobacter simplex TCCC 11037 (ASP) was selected as a model system for evaluating the effects of hydroxypropyl-beta-cyclodextrin (HP-beta-CD) on steroids 1-en-dehydrogenation process. By comparing the kinetic characteristics of CA dehydrogenation in HP-P-CD free or containing medium it was confirmed that this reaction followed the kinetics of produce inhibition, and the low solubility of CA was the limiting step of this bioconversion process at high substrate concentrations. However, the inclusion complex induced by HP-beta-CD could overcome this problem. At 32 degrees C, the solubility of CA and PA in 45 mg mL(-1) HP-beta-CD containing medium expressed 36.7- and 19.8-fold higher than that in HP-beta-CD free medium and the product inhibition could be effectively alleviated by HP-beta-CD. The favorable biocompatibility between HP-beta-CD and A. simplex Delta(1)-dehydrogenase was also an unnegligible contribution to the enhancement of this biotransformation. (C) 2009 Published by Elsevier B.V.