11α-hydroxylation of progesterone using modified alginate-immobilized cells

Abstract

The major disadvantage of using alginate-immobilized Aspergillus ochraceus for 11α-hydroxylation of progesterone is its instability in phosphate solutions. In this study, different gel-hardening methods were used to improve the stability of alginate gels. Addition of Fe 3+ and Fe 2+ ions increased the activity of hydroxylation, but Fe 2+ was not a good gelling agent. Replacement of CaCl 2 by FeCl 3 as the gelling agent increased the activity of the immobilized cells by about 33%. Hardening the alginate-immobilized cells with polyacrylamide (PAA) increased their stability in a 0.1 m phosphate buffer from 0.35 h to over 36 h. The productivity was increased by a factor of 1.8 compared to those without hardening, and the maximum yield was also increased from 84.3% to 90.8%. The physical properties and biocatalytic characteristics of PAA-hardened, immobilized cells were found to be feasible for application in a steroid bioconversion system.