Transesterification of soy lecithin by lipase and phospholipase

Soy lecithin was modified by enzymatic transesterification in a solvent-free system. 1,3-SpecificRhizomucor miehei lipase was found to be efficient in the transesterification with lauric acid and oleic acid, where oleic acid was more incorporated into soy lecithin. Phospholipase A₂ incorporated lauric acid hardly at all, but it hydrolyzed lecithin efficiently. The mixture of lipase and phospholipase A₂ (1:1, w/w) incorporated lauric acid to the same extent as did 1,3-specific lipase alone at the same total enzyme concentration. The main fatty acids replaced were palmitic and linoleic acids by 1,3-specific lipase and its mixture with phospholipase A₂, and linoleic and linolenic acids by phospholipase A₂ alone, suggesting an improved oxidative stability of the resulting product. Hydrolysis could not be prevented, but it could be regulated by incubation time and by enzyme dosage. The minimal water content for significant incorporation of lauric acid into lecithin was below 0.5% of the weight of the reaction mixture.