Production of egg yolk lysolecithin with immobilized phospholipase A2

Production of egg yolk lysolecithin was compared using free phospholipase A2 (PLA2) and immobilized PLA2 in alginate-silicate sol-gel matrix. Choice of solvent, water content, calcium, and temperatures changed the activity of the free and immobilized PLA2 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 PLA2 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 PLA2 reaction. However, with calcium ion, three distinctive regions were observed with free PLA2 reactions. Initially, in the micro-aqueous region of the ethanol-buffer system with calcium ion, the hydrolysis activity of PLA2 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 PLA2 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 PLA2. 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 immobilization of the enzyme remarkably increased thermal stability of the free enzyme, the immobilized PLA2 is more desirable to be used in the production of various lysophospholipids. It was successfully reused over 250 h.