Preparation Of Immobilized Lipase MAS1-H108A And Its Application In The Synthesis Of ?-Linolenic Acid-rich Triacylglycerols

Alpha-linolenic acid,as an essential polyunsaturated dietary fatty acid,has long been associated with reducing risks of heart arrhythmias,hypertension,coronary heart disease,diabetes,alzheimer disease and cancer.As a natural form of alpha-linolenic acid,triacylglycerols has a lot advantages such as good tastes and strong oxidation stabilities.Alpha-linolenic acid-rich triacylglycerols have both advantages of them.In recent years,synthesis of alpha-linolenic acid-rich triacylglycerols has attracted extensive attention due to its mild reaction conditions,high catalytic efficiency and environmental friendliness.However,most existed immobilized lipases are difficult to synthesize products with high content of alpha-linolenic acid and high content of triacylglycerols.It is necessary to further explore new lipases to make more contribution to the oil industry.A new lipase of MAS1 from marine Streptomyces sp.strain W007 is a thermostable and non-regiospecific lipase,which exhibited great potential in the synthesis of ?-3 PUFA-rich triacylglycerols during esterification of ?-3 PUFA-FAs and glycerol.Our team developed a mutant lipase of MAS1 named MAS1-H108 A with 1.6-fold enzymatic activity of wild type was a thermostable and nonregiospecific lipase.But there are few reports about its application in the catalytic modification of esters.In this study,MAS1-H108 A was immobilized and applied in esterification to prepare alpha-linolenic acid-rich triacylglycerols.The obtained products with highly content of alpha-linolenic acid and highly content of triacylglycerols were studied in basic physical and chemical properties.The main research results obtained were as follows:1.Fermentation and immobilization of lipase MAS1-H108A: Lipase MAS1-H108 A obtained by fermentation was immobilized on the resin ECR1030.Under the conditions of the ratio of enzyme with the resin ECR1030 was 41 mg/g,buffer pH was 7.5,the temperature was 30 ?,the immobilized MAS1-H108 A was 2335 U/g.Studies on the enzymatic properties of immobilized MAS1-H108 A were found that the optimum temperature of the immobilized MAS1-H108 A remained 65 ? and the optimum pH remained 7.5,but its temperature tolerance was significantly improved.2.Production of alpha-linolenic acid-rich triacylglycerols by immobilized MAS1-H108 A catalyzed esterification: The fatty acid from flaxseed oil was prepared by saponification,and the purity of alpha-linolenic acid was increased from 60.1% to 91.3%.The reaction conditions of ?-linolenic acid and glycerol in a solvent-free system have been further studied,and under the conditions of the immobilized MAS1-H108 A loading was 60 U/g,the reaction temperature of 55 °C,the molar ratio of glycerol to ?-linolenic acid was 1:3,the esterification degree reached 99.52%,and the content of triacylglycerols in the products was 96.31%,significantly better than the triacylglycerols content(8.97%)in the products catalyzed by Novozym 435.Moreover,the immobilized MAS1-H108 A retained 96% of its initial activity after the tenth cycle,which indicates that immobilized MAS1-H108 A has a good operational stability.3.Basic properties of alpha-linolenic acid-rich triacylglycerols and the studis on their oxidative stability: The acid value and peroxide value of the high purity of alpha-linolenic acid-rich triacylglycerols were 0.95 mg KOH/g and 2.61 meq/kg,respectively.In addition,it was found that compared with BHT and VE,adding TBHQ(0.2mg /kg)could better improve the oxidation stability of alpha-linolenic acid-rich triacylglycerols.