Extractive bioconversions of penicillin G by penicillin acylase were carried out using water-organic solvent two-phase systems.
Rekker's hydrophobic fragmental constant method and linear free energy relationship (LFER) were used in estimating partition coefficients of the substrate and the product in some two-phase systems. In this study organic solvents which have high partition coefficient for product (phenylacetic acid) which inhibits enzyme reaction were taken into account first and then, considering the general rule that solvents whose log P values are more than 2 are favored for enzyme activity, n-octanol (log P, 2.9) and cyclohexanol (log P, 1.5) were chosen for the experiment. Cyclohexanol turned out to be useless due to its serious deactivation effect on enzyme. Octanol worked well especially when pH was not controlled.
Thermodynamic theory could successfully predict the 6-APA yield when the reaction was completed so fast that β-lactam ring degradation was negligible.
