Enzymatic Preparation Of Medium-and Long-chain Fatty Acid Triacylglycerols And Its Effect On Lipid Metabolism Of Mice

Fat is an important part of the human diet,which provides energy for the body and also plays diverse roles in health.Excessive intake of fat and other unhealthy lifestyles can lead to obesity and related chronic diseases.Medium-and long-chain triacylglycerols(MLCT)are a special class of structural lipids that can provide energy to the body while avoiding fat accumulation.Most of the MLCTs on the market are synthesized from caprylic/capric acid and have no specific molecular structure.In this study,MLCTs with special structures were prepared using lauric acid,palm stearin,and algal oil as raw materials.Two kinds of MLM(Middle-long-middle)MLCTs were enzymatically synthesized,which were rich in 1,3-lauric-2-palmitoylglycerol(LaPLa)and rich in lauric acid and docosahexaenoic acid(DHA).The effects of LaPLa-rich MLCT on lipid metabolism in mice were explored.The main results of the study were listed as follows:(1)Enzymatic preparation and analysis of physicochemical properties of LaPLa-rich MLCT: Taking the content of LaPLa as an index,sn-1,3 specific lipase was used to catalyze the lauric acid to hydrolyze palm stearin to synthesize the target product.Three lipases(RM IM,TL IM,AO IM)were compared,and AO IM had the highest catalytic efficiency.Using AO IM as the catalytic enzyme,the present study explored the optimum reaction conditions,and found that under the conditions of a substrate molar ratio of 1:10(palm stearin: lauric acid),an enzyme loading of 10%(w / w),a reaction temperature of65℃,a water bath shaker speed of 200 rmp,and a reaction time of 2.5 h,the content of LaPLa can reach(40.59 ± 0.29)%.Compared with palm stearin,the crystallization temperature and melting temperature of purified MLCT are decreased,and the acid value and peroxide value meet the standards of edible oil.(2)Enzymatic preparation and analysis of physicochemical properties of MLCT rich in lauric acid and DHA: This study used lauric acid and algal oil as raw materials,and the AO IM as catalyst,the present study explored the optimum conditions for enzyme-catalyzed synthesis of MLM MLCT.Under the conditions that the reaction temperature was 65 ℃,the substrate molar ratio was 1: 8(algal oil: lauric acid),the enzyme load was 8 %(w / w),and the water bath oscillator was rotated at 150 rmp.the reaction time was 2.5 h,the lauric acid participation rate was(28.91±0.14)%,the total DHA content was(44.68±0.07)%,the lauric acid content at the sn-2 position was(5.13±0.34)%,and the DHA content at the sn-2 position was(52.55±0.39)%,and also inthis condition,the mixture of the product did not contain glyceryl trilaurate(LaLaLa).After purification,both the acid value and peroxide value of the MLCT meet the standards of edible oil..(3)Effect of LaPLa-rich MLCT on lipid metabolism in mice: In mice model of the present study,60 C57B/L6 mice aged 10 weeks were randomly devided into 4 groups,and fed with normal chow diet(NCD),high-fat diet(HFD),HFD of which lard was replaced by palm stearin(PS),HFD of which lard was replaced by MLCT for 10 weeks.After 10 weeks of intervention,compared with the other three groups,mice fed with MLCT showed significantly increased body weight and increased serum GOT and GOP levels.There were no significant differences between the four lipid levels in the HFD and PS group.In oral glucose tolerance test,mice form HFD and MLCT group showed equivalent glucose tolerance.Though the epididymal fat cell size of mice in MLCT group trended to increase,but no significant difference was found when compared with HFD group.In summary,the prepared MLCT has a good weight gaining effect,especially more significant than the HFD group.At the same time,some lipid metabolism indicators brought by the weight gain have not changed significantly compared with the HFD group.