Transesterification Of Soybean Oil Catalyzed By Immobilized Lipase

Lipase, as a sort of catalyst in the transesterification reaction between triglyceride andshort-chain alcohols, can be obtained from various sources. However, the free enzyme candissolve easily in water and gather into cluster in organic solvents; on the other hand, it ishard to be separated to reuse. The immobilized enzyme could not only enlarge the contactsurface between enzyme and substrate to benefit to the diffusion of substrate molecule, butalso enhance the separation and application of immobilized enzyme.In this article, the non-polar macroporous adsorption resin NKA works as a carrier, and themethod of immobilization is physical adsorption, the condition of immobilization is optimized.Then we optimize the condition of transesterification reaction by use of soybean oil as the rawmaterial and immobilized lipase as catalyst. The role of silica gel in the transesterificationreaction and the operational stability of the immobilized lipase are investigated.The results are concluded as following:(1) The optimum conditions for macroporous resin to immobilize lipase are as follows:adsorption is performed at1:2ratio of lipase to resin in buffer at pH7.4for12h. Under theseconditions, the activity of immobilized lipase could reach71.30U/g.(2) The optimum conditions of immobilized lipase catalyzed transesterification reactionshow that: adding petroleum ether to the reaction system could gain a higher conversion rate,the reaction system does not need to add additional water, the reaction is conducted at40℃for48h in a mixture of4g soybean oil and3mL petroleum ether, the conversion rate couldreach52.29%.(3) Mechanical agitation on the substrate soybean oil could significantly improve theconversion rate, which could improve14%after1h agitation and24h reaction compared withthe unstirred group.(4) Adding silica gel could improve the conversion rate and extend the life of immobilizedlipase. The reaction is conducted at1:13.3ratio of silica gel to oil with1%water at40℃, thesilica gel is added at the start of the reaction, the conversion rate has improved9%on average after continuously reacting for4batches (96h).