Immobilization Of RML Onto The Organic Functionalized SBA For Diacylglycerols Synthesis Through Glycerolysis

DAG not only has the same taste and flavor as traditional fats,but also has special physiological functions such as preventing body fat accumulation,effectively controlling weight gain,lowering blood lipid level and so on.Compared with the chemical method,DAG prepared by enzymatic method has the advantages of applying mild reaction conditions as well as high selected and catalytic efficiency.Immobilized enzyme is the first choice of enzymatic preparation of DAG,and the introduction of organic functional groups via post-grafting modification of the mesoporous material SBA dramatically enhancing the performance of the mesoporous material SBA-supported enzyme.In this paper,the study mainly is focus on the RhodopsiaRubrum Lipase?RML?supported on the organic functional group modified mesoporous material SBA,and its catalytic glycerolysis reaction for the synthesis of DAG.The main research contents and results of the paper are as follows:?1?Post-grafting modified mesoporous material SBA was used to immobilize RML.The structure of modified SBA and immobilized enzyme were characterized by X-ray diffraction?XRD?,X-ray photoelectron spectroscopy?XPS?and Fourier transform infrared spectroscopy?FT-IR?,then compared with unmodified SBA.The results showed that the organic functional groups were successfully modified on the surface of SBA without destroying the pore structure of SBA,and the RML was successfully loaded into the pores of SBA with organic functional groups.?2?Sixteen organic functional groups were used to modify SBA and then loaded with RML to obtain R-SBA-RML immobilized enzyme?R is an organic functional group?.The enzymatic properties of the obtained immobilized enzyme were studied.As a result,it was found that N-dodecyl(C₁₂H₂₇N)-SBA-RML had the highest enzyme activity?13211.11±523.87U/g?,which was 66 times of the activityas SBA-RML.C₁₆H₃₃-SBA-RML retained 100%of the enzyme activity after being heated at 70°C in n-hexane and solvent-free systems,while C₁₂H₂₇N-SBA-RML and 3-glycidyl(C₆H₁₁O₂)-SBA-RML,3-aminopropyl?C₃H₈N?-SBA-RML and methyl?CH₃?-SBA-RML retained more than 57%of enzymatic activity under the same heating conditions.In terms of reusability,C6H11O2-SBA-RML and3-mercaptopropyl?C₃H₇S?-SBA-RML retain 100%activity after five-time usage.Most of the immobilized enzymes studied had the highest enzyme activity under alkaline conditions?pH7.0 and pH8.0?,whereasC₃H₈N-SBA-RMLand3-methacryloyloxy(C₇H₁₁O₂)-SBA-RML gained the highest enzyme activity under acidic conditions?pH4.0 and pH5.0?.?3?The properties of three kinds of ionic liquid modified SBA-loaded RML enzymes were studied,and the immobilized enzyme modified by octyl ionic liquid reached 3422 U/g.The lowest enzyme activity of CH₃-IL-SBA-RML was?1422.22±401.85 U/g?,but still significantly better than the unmodified SBA-RML enzyme activity?200±83.89U/g?.C₄H₉-IL-SBA-RML retains 100%enzyme activity in terms of thermal stability.CH₃-IL-SBA-RML retains 100%activity after five reactions in terms of reusability.?4?The end-product of immobilized enzyme was studied for glycerolysis to prepare DAG.The results showed that the catalytic effect of glycerolysis?DAG content above 45%?was significantly higher than that of unmodified SBA directly loaded RML?15.45%DAG content?after loading SML with organic functional groups.After studying partly of these processes aboutimmobilized enzymes catalyze the reaction of glycerolysis,the results showed that the content of DAG in(C₁₆H₃₃)-SBA-RML and aniline methyl?C₇H₉N?-SBA-RML was the highest at the eighth hour,and the content of n-octadecane(C₁₈H₃₇)-SBA-RML,C4H6ON-SBA-RML,n-octyl(C₈H₁₇)-SBA-RML and C₇H₉N-SBA-RML had the highest DAG content at the tenth hour.In the reusability experiments of C₁₆H₃₃-SBA-RML,C₇H₉N-SBA-RML and n-butyl?C₄H₉?-SBA-RML,it was found that the DAG content and the triglyceride?TAG?conversion were less than 20%after five reactions,indicating lower capability of reusable.?5?Some functional groups were selected to modify SBA and then loaded with RML.Among the above experiments,the enzymatic properties and catalytic glycerolysis were studied to prepare DAG.The results showed that comparing with single functional group modified SBA-loaded RML,the enzyme activity of SML-loaded RML with two functional groups modified at the same time?composite functional group?showing different level drop down,meanwhile the thermal stability and the reusability were better.But the catalytic effects of glycerolysisfrom single functional group modified and composite functional group modified are quiet equivalent.