Biocatalytic oxidation of a hydrophobic compound cholesterol into androsta-diene-dione (ADD) by Mycobacterium sp., biocatalytic reduction of chiral alcohol from prochiral ketone mediated by Saccharomyces cerevisiae (baker’s yeast), which mainly involves a cofactor regeneration with the viability cell, and biotransformation of benzaldehyde into L-phenylacetylcarbinol (PAC) by whole cell of Saccharomyces cerevisiae, which needs the viability cell to produce a cosubstrate pyruvic acid, were studied in cloud point system as models . The results indicate that cloud point system used as a novel two-phase partitioning system for biotransformation has a practical potential. However, the utilization of cloud point system for biotransformation is in its infancy and will need further study of more model reactions besides about the process control and the downstream process before it will be used in an industrial application.