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 enzym es from Humicola lanuginosa, Rhizopus delemar and Candida rugosa displ ayed appreciable activity. Solvent polarity was the largest single fac tor affecting activity. The H. lanuginosa sample was most active in po lar solvents. The R delemar preparation was most active in polar (2 he xanone) and nonpolar (decane) solvents and least active in solvents of intermediate polarity (hexane). The solvent dependence of the activit y of the C. rugosa enzyme varied with the ratio of substrate to enzyme . Different degrees of activity were retained by the three enzymes aft er passive immobilization on Celite, controlled pore glass, polypropyl ene and Amberlite XAD-7 resins. No single resin yielded the best retai ned activity for all three preparations. When examined in 2-octanone, hexane and isooctane, the Celite immobilized R delemar and H. lanugino sa enzymes exhibited highest activity in 2-octanone, while immobilized C. rugosa was most active in isooctane. The water content at which ma ximum activity was observed was relatively independent of sol vent pol arity and the amount of catalyst but was proportional to the amount of PC in the reaction. The retention of activity by immobilized Rhizomuc or miehei lipase (Lipozyme) during multiple hydrolytic cycles required a reduction in the water content of the system below that yielding op timal activity in a single cycle.