Immobilization of Lipase for Effective Interesterification of Fats and Oil in Organic Solvent

Abstract

In order to investigate quantitatively the interesterification reaction, triolein and stearic acid were used as substrates and eight commercially available lipases were tested for their suitability for the reaction. Three fungal lipase preparations were found to be suitable. The hydrolytic activity of the commercial lipases was tested with olive oil, and it was noted that there was no correlation between their hydrolytic and interesterification activities. Among the lipases tested, Mucor miehei lipase was chosen for further study because of its high protein content and its relatively high hydrolytic and interesterification activities, both of which are required for effective interesterification. The effect of water activity on the interesterification reaction was investigated. Interesterification activity was shown to be maximum at the water activity of 0.25. As the water activity of the lipase increased, hydrolysis of triglyceride was accelerated. At zero water activity, high conversion was achieved, although interesterification activity was relatively lower than that at the water activity of 0.25. A new and simple immobilization method was developed in order to render hydrophobicity to the lipase and hence to improve the interesterification activity of the lipase. The lipase was immobilized covalently with glutaraldehyde or with six alkyl chains as spacers onto Florisil (magnesium silicate, an inorganic matrix). Interesterification activities of the immobilized lipase with the hydrophobic spacers were increased against that of free lipase. The increase of activity was up to 88-fold that of the original activity of free lipase when the spacer was 7-aminoheptanoic acid. Relatively high stability of the immobilized lipase was shown in a continuous packed bed column reactor with a half-life of 97 days.