Study On Enzymatic Preparation Of Different Chain Length Of Diacylglycerols And Their Lipid Metabolism Function

Diacylglycerol?DAG?is a structural lipid formed by the combination of fatty acid and glycerol in an esterification reaction,in which two hydroxyl groups in an alcohol are replaced by fatty acids.Numerous studies have shown that diacylglycerols played an important role in lowering blood lipid levels,preventing fat accumulation and reducing body weight,and have received widespread attention.In this paper,peanut oil and coconut oil were used as raw materials to synthesize peanut oil diacylglycerol and coconut oil diacylglycerol by enzyme method.The effect of lipid metabolism between mice with different chain length diacylglycerols were studied.The main research contents and results are as follows:1.The study compared different solvent systems,solvent-free systems and different immobilized lipases to catalyze the synthesis of diacylglycerols from peanut oil and glycerol.According to the four factors of substrate molar ratio?glycerol:peanut oil?,enzyme loading,reaction time and reaction temperature,determined the content of diacylglycerols and triacylglycerols in the product to optimize the reaction conditions.The results showed that the solvent-free system had the best reaction effect compared with organic solvents and ionic liquids.In the solvent-free system,the optimal reaction conditions for the production of DAG by peanut oil glycerol hydrolysis by Novozyme 435 were as follows:substrate molar ratio?glycerol:peanut oil?was 2:1,the enzyme loading was 6%,the reaction temperature was 70?,and the reaction time was 12h.Under these conditions,the DAG content was 48.56%,and the TAG content was 20.12%.2.The research was carried out to purify peanut oil diacylglycerol by molecular distillation technology,and to determine the changes of glyceride composition,fatty acid composition,glycidyl ester,nutrients and flavor components before and after synthesis and purification.The results showed that the diacylglycerol with a purity of85.82%and a yield of about 18.54%could be obtained after secondary molecular distillation at 220?.The fatty acid composition after molecular distillation didn't change significantly,mainly composed of oleic acid and linoleic acid,but after molecular distillation.The content of saturated fatty acids increased?P<0.05?,and the content of trans fatty acids also increased from 0.75%of peanut oil to 1.2%of the total product.When the temperature exceeded 220?,the content of glycidyl ester increased sharply from 0.25 mg/kg at 180?to 9.77 mg/kg at 240?.The study found that its content increased exponentially with temperature,y=0.0985e^0.9242x,R²=0.9796,so the temperature of the secondary molecular distillation shouldn't exceed220?.The nutrients were reduced before and after molecular distillation.The loss of vitamin E was the highest,reaching 40.69%,and the loss rate of sterol was 21.96%.The main flavor substances of peanut oil are pyrazine compounds,furan compounds and aldehyde compounds,which were roasted and oily.The synthetic diacylglycerols were reduced by volatile substances after molecular distillation.The main volatile substances were aldehydes,which were oily.The coconut oil diacylglycerol obtained by the optimal synthesis conditions and purification process contains 60.94%of diacylglycerol and 60.44%of medium chain fatty acid.3.The effects of different chain length diacylglycerols synthesized on body fat,blood lipids and tissue lipid metabolism related enzymes in C57BL/6J mice were investigated by animal experiments.The results showed that compared with the high-fat peanut oil group,the body weight,body length,tissue weight and liver and serum triacylglycerol?TG?and leptin content of peanut oil DAG group,coconut oil DAG group and coconut oil group were significantly lower than those of high fat peanut oil group?P<0.05?.It indicated that the long-term feeding of containing high-fat DAG oil had a better effect on the body weight and blood lipids of the mice,but the peanut oil DAG group and the coconut oil DAG group had significant differences in body weight,and other indexes were similar.Compared with triacylglycerol?peanut oil and coconut oil?,fatty acid synthase?FAS?and acetyl-CoA carboxylase?ACC?in peanut oil DAG and coconut oil DAG group were significantly lower?P<0.05?,indicating that diacylglycerols could reduce the synthesis of fatty acids and inhibit the accumulation of fat.,while the level of hormone sensitive lipase?HSL?in the white adipose tissue of the DAG oil group was higher than that of the triacylglycerol group,which accelerated the decomposition of fat.However,it had no effect on the expression of tumor necrosis factor?TNF-??and adiponectin.Medium chain diacylglycerol worked better than long chain diacylglycerol.The effect of coconut oil DAG on improving body fat metabolism was mainly the action of diacylglycerol.The combination of medium chain fatty acids had a certain effect,but it was not obvious.