PREDICTION OF WATER-ADSORPTION CURVES FOR HETEROGENEOUS BIOCATALYSIS IN ORGANIC AND SUPERCRITICAL SOLVENTS

In the framework of heterogeneous biocatalysis in non-aqueous media, k nowledge of water adsorption curves is necessary for the choice of ope rating conditions. Indeed, water content plays a crucial role in the p erformance of such enzymatic reactors. A method to estimate water adso rption curves in biphasic solid-fluid systems is proposed here. It is grounded on the hypothesis that the water adsorption of the solid is n ot dependent on the solvent and on the theoretical evaluation of water activity in the solvent. It is tested in the case of 3-methyl-1-butan ol, 5-methyl-2-hexanone and supercritical carbon dioxide as solvents a nd an immobilized enzyme, Lipozyme(R), as the solid phase. The method proved to be in good agreement with experiments. The method uses only a single experimental curve but necessitates the development of numeri cal modeling of thermodynamics. However, a simplified method, restrict ed to the range-hydrophobic to weakly hydrophilic solvent-is also prop osed and tested. Copyright (C) 1996 Elsevier Science Ltd.