ENZYMATIC PHOSPHATIDYLCHOLINE HYDROLYSIS IN ORGANIC-SOLVENTS - AN EXAMINATION OF SELECTED COMMERCIALLY AVAILABLE LIPASES

Eight commercial lipase preparations were examined for the ability to hydrolyze phosphatidylcholine (PC) in hexane solutions. Only the enzymes from Humicola lanuginosa, Rhizopus delemar and Candida rugosa displayed appreciable activity. Solvent polarity was the largest single factor affecting activity. The H. lanuginosa sample was most active in polar solvents. The R delemar preparation was most active in polar (2 hexanone) and nonpolar (decane) solvents and least active in solvents of intermediate polarity (hexane). The solvent dependence of the activity of the C. rugosa enzyme varied with the ratio of substrate to enzyme. Different degrees of activity were retained by the three enzymes after passive immobilization on Celite, controlled pore glass, polypropylene and Amberlite XAD-7 resins. No single resin yielded the best retained activity for all three preparations. When examined in 2-octanone, hexane and isooctane, the Celite immobilized R delemar and H. lanuginosa enzymes exhibited highest activity in 2-octanone, while immobilized C. rugosa was most active in isooctane. The water content at which maximum activity was observed was relatively independent of sol vent polarity and the amount of catalyst but was proportional to the amount of PC in the reaction. The retention of activity by immobilized Rhizomucor miehei lipase (Lipozyme) during multiple hydrolytic cycles required a reduction in the water content of the system below that yielding optimal activity in a single cycle.