Oxidation of benzyl alcohol by whole cells of <i>Pichia pastoris</i> and by alcohol oxidase in aqueous and nonaqueous reaction media

Abstract

The low substrate specificity of alcohol oxidase from Pichia pastoris makes this enzyme system of potential biotechnological interest. Whole cells of Pichia pastoris are able to oxidize benzyl alcohol to benzaldehyde in aqueous reaction media. The low water solubility of the reactant and product of this bioconversion, combined with the ability of both to strongly inhibit the reaction, favor the use of nonaqueous reaction fluids. Purified alcohol oxidase was shown to function in a number of 2-phase reaction systems of varied aqueous to organic phase ratios (0.01-0.05 v/v). The apparent V(max) and K(m) were 5.26 g/Lh and 7.41 g/L respectively, for the oxidation of benzyl alcohol to benzaldehyde in hexane containing 3% aqueous phase. The volume of the aqueous phase had a strong effect on the reaction, with an aqueous: organic ratio of 3-5% found to be optimum. The enzyme could be firmly immobilized on DEAE-Biogel (Biorad) to enhance stability and biocatalyst recovery.