Transesterification Of Vegetable Oil Catalyzed By Immobilized Lipase

The activity and stability of lipase were enhanced by immobilization of lipase and pretreatment to immobilized lipase in this study. The effect of carriers and adsorption conditions on immobilization of lipase and the effect of pretreatment on activity and stability of immobilized lipase were investigated. In addtion, the immobilized lipases were used to catalyze the transesterification of refined soybean oil and methanol to produce fatty acid methyl ester. The results are shown as follow.The active carbon of40mesh, silica gel and DM-130macroporous resin were suitable for immobilization of lipase. The concentration and adsorption time of lipase would affect the lipase adsorption. The pH and temperature would affect the activity of immobilized lipase, but not the lipase adsorption. The immobilized lipase could reach high activity32U/g, which was prepared by shaking the mixture of0.05mg/mL lipase solution at pH7.0and DM-130macroporous resin at150rpm,30℃for2hours, while the values were observed as65U/g and39U/g respectively when the lipase was immobilized on active carbon and silica gel for1hour under the same conditions as the adsorption on DM-130macroporous resin.The activity and stability of immobilized lipase could be improved by pretreatment with organic solvent. Acetone,1-propanol,2-propanol and ethyl acetate could markedly activate the immobilized lipase, and the1-propanol and ethyl acetate could improve the thermal and operational stability of immobilized lipase. Compared with untreated immobilized lipase, treated immobilized lipase displayed obvious enhancement of reaction characteristics which included the activities increased1.93to2.25times, the half-life time prolonged3.2to8.4hours, the operativing lives extended3to5batches, the storage time lengthened more then90days and the residual activites at60℃was from53.4%to81.7%of its initiate activity when the lipase immobilized on silica gel or DM-130macroporous resin was treated in2-propanol for1hour, or the lipase immobilized on active carbon was treated in ethyl acetate for1hour.Although the crosslinking by glutaraldehyde could reduce the activity of immobilized lipase, it was able to significantly improve its stability. Compared with untreated immobilized liapse, cross-linked immobilized lipase displayed obvious enhancement of reaction charact-eristics which included the half-life time prolonged4.3to9.2hours, the operating lives extended3to4batches and the residual activities at60℃was from53.4%to68.5%of its initiate activity when the immobilized lipases were cross-linked by0.3%glutaraldehyde for10min.To soak the immobilized lipase in substrate soybean oil could increase the conversion rate of fatty acid methyl ester. The conversion rate was increased from82.9%to89.9%when the lipase immobilized on active carbon, silica gel G and DM-130macroporous resin was soaked in soybean oil at30℃for8hour.