Immobilization conditions of alkaline lipase and its application in synthesis of biodiesel

Alkaline lipase was immobilized on modified silica gel and glutaraldehyde was used as cross-linking agent. The optimal conditions for lipase immobilization were as follows: glutaraldehyde concentration of 0.8 g/L the ratio of lipase to the resin in weight as 30 U/g. The activity recovery of the enzyme was above 90% under optimal conditions. Effects of different solvents, the amount of immobilized lipase, water content, molar ratio of different substrate concentrations and fed-batch methods for methanol on technology of biodiesel synthesis by immobilized alkaline lipase were studied. Results showed that esterification ratio of the substrates achieved 82% catalyzed by immobilized alkaline lipase at 40℃ for 8 h under the conditions as follows: 20 mL n-hexane, lipase amount of 7.5 g (12 U/g), water content of 4%, molar ratio of fatty acid to methanol of 1:1.2 and methanol fed-batch for three times.