IMPORTANCE OF SOLUTE PARTITIONING IN BIPHASIC OXIDATION OF BENZYL ALCOHOL BY FREE AND IMMOBILIZED WHOLE CELLS OF PICHIA-PASTORIS

Using free and immobilized whole cells of Pichia pastoris, the biocata lytic oxidation of benzyl alcohol was investigated in different two-ph ase systems. This reaction was strongly influenced by both the substra te and product inhibitions, and the production rate of benzaldehyde in the aqueous system became maximum at the initial substrate concentrat ion of ca. 29 g/L with the aldehyde formation less than 4 to 5 g/L eve n after a longer reaction period. The reaction rates in the two-liquid phase systems were predominantly determined by the partitioning behav iors of the substrate and product between the two phases rather than b y enzyme deactivation by the organic solvents. In the two-liquid phase systems, consequently, the organic solvent acted as a reservoir to re duce these inhibitory effects, and it was essential to select the orga nic solvent providing the optimal partitioning of the substrate into t he aqueous phase as well as the preferential extraction of the product into the organic phase. The whole cells immobilized in a mixed matrix composed of silicone polymer [>50% (v/v)] and Ca alginate gel (<50%) worked well in the xylene and decane media, providing comparable activ ities with the free cells. The production rate of aldehyde was also in fluenced by the solute partitioning into the hydrophilic alginate phas e where the cells existed. (C) 1994 John Wiley & Sons, Inc.