Application of Immobilized Biocatalysts to Bioconversion in Hydrophobic Conditions
New methods to entrap biocatalysts with photo-crosslinkable resin prepolymers and urethane resin prepolymers of either hydrophilic or hydrophobic character have been developed. Steroids having a hydrophilic group at C-17 position were dehydrogenated (4-androstene-3,17-dione to androstene-1,4-diene-3,17-dione and dehydroepiandrosterone to 4-androstene-3,-17-dione) in an organic solvent by Nocardia rhodocrous cells entrapped with either hydrophilic prepolymers. In the cases of highly hydrophobic steroids having an aliphatic side chain at C-17 position, such as cholesterol, β-sitosterol and stigmatsterol, however, transformation to the corresponding 3-keto-Δ4 -steroids was achieved in a non-polar organic solvent only by the cells entrapped with hydrophobic prepolymers. Thus, advantage of hydrophobic gels is the bioconversion of highly hydrophobic compounds has been observed clearly. The steroid transformation activities of the gel-entrapped cells were closely correlated to the partition coefficients of substrates (and in some cases, to those of cofactors) between gels and external solvents.
KeywordsPartition Coefficient Aliphatic Side Chain Immobilize Biocatalyst Phenazine Methosulfate Entrap Cell
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