Correlation of biocatalytic activity in an organic-aqueous two-liquid phase system with solvent concentration in the cell membrane.

Results presented here show that loss of progesterone 11 alpha-hydroxylase activity in Rhizopus nigricans in aqueous-organic two-liquid phase and cosolvent systems correlates well with the concentration of solvent in the cell membranes. Rhizopus nigricans is shown to retain full 11 alpha-hydroxylase activity at saturating aqueous phase concentrations of hexane and the higher primary alcohols. This reflects their inability to attain a critical concentration in the cell membranes. The relationship between our own findings and the previously described correlation of the logarithm of the partition coefficient with activity retention is explained and design parameters are proposed that may be used to select solvents for future biocatalytic systems.