Study on Lipozyme TL IM-catalyzed esterification of oleic acid and glycerol for 1,3-diolein preparation

• Lipozyme TL IM catalyzed the esterification of glycerol and oleic acid to produce 1,3-DO.
• In hydrophobic system (log P ≥ 2.5), the hydrophobic products accumulated most.
• With temperature decreased, the 1,3-DO/DO value increased.
• The reaction proceeding better when water activity being closer to its optimal point.
• Under the optimum conditions, 50% DO yield could be achieved with 90% 1,3-DO content.

It is well recognized that oils with a high 1,3-diacylglycerol content has the advantage of suppressing the accumulation of visceral fat and preventing the increase of body weight, and the synthesis of 1,3-diacylglycerol has attracted considerable attention. It is important to explore various methods for 1,3-diacylglycerol synthesis. In this work, the potential of using lipase Lipozyme TL IM-mediated esterification of oleic acid with glycerol for 1,3-diolein preparation was explored. The effect of solvent, oleic acid feeding strategy, online water removal, water activity, temperature, molar ratio of oleic acid to glycerol and enzyme dosage on the diolein yield and 1,3-positional selectivity of the lipase was investigated systematically. It was found that solvent, water activity, temperature, substrate molar ratio and enzyme dosage had varied influence on diolein yield as well as the positional selectivity of the enzyme. With the increasing water activity and solvent’s log P, diolein yield and the positional selectivity increased to a maximum value at a certain point, then had a decrease. It seems that in the process with multiple reaction involved, reactions trend to generate the products with log P closer to the system log P. In addition, with the water activity being closer to its optimum water activity, the hydration degree of the enzyme would be closer to its optimum hydration degree, and the activity might be closer to the highest enzyme activity, causing the reaction proceeding better. Under the optimum conditions (1.8 g Lipozyme TL IM was used to catalyze the reaction with 9.8 g oleic acid and 0.72 g glycerol in the system with 8.4 g toluene, and 6.4 g molecular sieve to remove water), a total diolein yield of about 50% could be achieved with the content of 1,3-diolein in the total diolein over 90%.

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