Bioconversion of lipophilic compounds by immobilized microbial cells in organic solvents

Microbial cells were gel-entrapped with photo-crosslinkable resin prepolymers or urethane prepolymers, respectively. The resulting gels have different tailor-made hydrophobic or hydrophilic character. They were used for successful bioconversion of hydrophobic steroids and terpenoids in watersaturated mixtures of organic solvents. The experiments show the influence of the hydrophobicity of the gels and the polarity of the solvent mixtures, respectively. Use of hydrophobic gels and less polar solvents is preferable for bioconversion of hydrophobic compounds. The selective formation of a desired product among diverse products from a single substrate by appropriate use of hydrophobic or hydrophilic gels is possible. In each case, tests should be made to select the appropriate gel and solvent mixture. Bioconversions tested are: dehydroepiandrosterone to 4-androstene-3,17-dione; cholesterol to cholestenone; β-sitosterol to β-sitostenone; stigmasterol to stigmastenone; pregnenolone to progesterone; testosterone to Δ¹-dehydrotestosterone or 4-androstene-3,17-dione, respectively; all with immobilized cells of Nocardia rhodocrous; and stereoselective hydrolysis of dl-menthyl-succinate to yield l-menthol with immobilized cells of Rhodotorula minuta var. texensis.