Production of egg yolk lysolecithin with immobilized phospholipase A2

Production of egg yolk lysolecithin was compared using free phospholipase A(2) (PLA(2)) and immobilized PLA(2) in alginate-silicate sol-get matrix. Choice of solvent, water content, calcium, and temperatures changed the activity of the free and immobilized PLA(2) a lot, owing to their effects on the catalytic properties of the enzyme as well as the conformational change of lecithin in ethanol-buffer mixture. Free PLA(2) shows typical microemulsion kinetics in ethanol-buffer system. The effect of the water content on the enzyme reaction was greatly influenced by the presence of calcium ion. In the absence of calcium ion, certain optimal water content for the production of lysolecithin always exists in the free PLA(2) reaction. However, with calcium ion. three distinctive regions were observed with free PLA(2) reactions. Initially, in the micro-aqueous region of the ethanol-buffer system with calcium ion, the hydrolysis activity of PLA(2) was proportional to the water content. Beyond the region, concave type of activity profiles were observed as the water content increases. As the water content increases further, the hydrolysis rate of the PLA(2) abruptly decreased by the phase separation. On the contrary, in case of immobilized enzyme, optimal water content for the production of lysolecithin exists regardless of the presence of calcium ion. The calcium ion was essential for achieving the maximum activity of both free and immobilized PLA(2). The addition of calcium ion not only affected the catalytic activity of the enzyme but also was necessary to improve the enzyme stability. As the im-mobilization of the enzyme remarkably increased thermal stability of the free enzyme. the immobilized PLA(2) is more desirable to be used in the production of various lysophospholipids. It was successfully reused over 250 h. (C) 2001 Elsevier Science Inc. All rights reserved.