Lipase Modification Of Soybean Oil To Produce Structured Lipids

Structured lipids (SLs) have special functions or nutritional properties for edible or pharmaceutical purposes, and they are being attracted more and more attention in terms of both their application and production, but there are very few reports on SLs in China. In this study, the procedure of the production of SLs with soybean oil and caprylic acid (CA) catalyzed by lipase was investigated. The main results were as follows:The lipase-lipozyme RM IM, suitable for acidolysis reaction, was chosen and its effect was examined. The key factors and their available ranges were investigated. Optimal reaction conditions by single factor test were: reaction temperature 40℃, immobilized lipase 472mg, mole ratio of substrates (CA/soybean oil) 6/1, added water 10%, reaction lasting for 24h. Under the conditions, the incorporation of CA could reach up to 43 mol%.Considering that the interaction of the key factors might affect lipase-catalyzed acidolysis of soybean oil, response surface methodology was used to optimize the production conditions of SLs. The results showed that when decision coefficient was at 98.34%, the optimal level at highest CA incorporation was reaction temperature 35.8℃, enzyme load 11.9%, substrate ratio 5.7, added water content 15.4% and reaction time 20.4h, and under the condition, the measured incorporation of CA was up to 44.9 mol%, which accorded with the predicted value 45.7 mol%. This indicated that using response surface methodology to optimize the reaction conditions of lipase-catalyzed acidolysis of soybean oil to produce SLs was fairly precise and more effective.In order to shorten the reaction time, caprylic methylester was used to replace CA to synthesize SLs. While the other conditions keep invariable, it needs only 16h to produce the same SLs for interesterification while acidolysis needs 24h. If go on with the interesterification, the incorporation of CA can be up to 60.05 mol%.The result by catalyzing at the optimal reaction with immobilized lipase-lipozyme RM IM shows that after 40 cycles, 90% residual activity of the immobilized lipase was remained.The fatty acid composition of the SLs analyzing showed that there was a small quantity of CA incorporation in the sn-2 of the SLs, suggesting that the acyl migration occurred, but in small quantity.