THE ENZYMATIC-HYDROLYSIS OF TRIGLYCERIDE-PHOSPHOLIPID MIXTURES IN AN ORGANIC-SOLVENT

The abilities of four commercially available lipolytic enzymes [three immobilized lipases-lipozyme IM-20, SP-435 (Novo Biolabs, Danbury, CT), and AY-30/Celite (Amano Enzyme Co., Ltd., Troy, VA)-and a nonimmobilized Amano phospholipase B preparation] to hydrolyze mixtures of triacylglycerols (TG) and phospholipids (PL) were determined. All of the lipases hydrolyzed both types of substrates in water, with maximum rates of TG hydrolysis exceeding those of PL hydrolysis by between 20- and 200-fold. The phospholipase B preparation was inactive against both TG and PL in water. All the enzymes showed some activity against lipids in hexane. The amount of activity was sharply dependent on the amount of water added to the reaction. Lipozyme IM-20 and AY-30/Celite hydrolyzed both TG and PL in hexane. Their estimated initial activities were between 10- and 100-fold lower than those in water. Complete hydrolysis of the TG (measured as the hydrolysis of at least one ester bond in each molecule) was achieved, whereas only 40-60% of the phosphatidylcholine (PC) and phosphatidylethanolamine (PE) were hydrolyzed. Lipase SP-435 was inactive against TG in hexane but hydrolyzed PC at a rate comparable to that seen in water, and it achieved complete hydrolysis of this substrate. Amano phospholipase B was inactive against TG in hexane but completely hydrolyzed the PC. The abilities of the enzymes to hydrolyze the TG, PC, and PE components of soybean soapstock, a by-product of edible oil production, were also examined. Lipozyme IM-20 hydrolyzed all the TC and a fraction of the PF in soapstock. SP-435 and AY-30/Celite were active only on soapstock that had been acidified prior to being dissolved in hexane. SP-435 displayed significant activity only toward PE under these conditions, whereas AY-30/Celite was active only toward TG. Phospholipase B was inactive against soapstock in hexane. The identity of the acid used in the acidification of soapstock affected the degree of hydrolysis by AY-30/Celite, with nitric and hydrochloric acids giving the best activity.