| Owning to unique structural characteristics, the catalytic ability and operational stability of lipases can be greatly improved when lipase is immobilized. In this paper, two different methods were employed to immobilize lipase from Candida sp99-125obtained in our own lab. Optimum immobilized conditions were investigated, characteristic of different immobilization lipase was studied. Apply SEM on immobilized lipase to speculate the changing of lipase structure.Candida sp.99-125lipase was immobilized on chitosan by chemical covalence. Lipase was first immobilized to chitosan beads by activating its hydroxyl groups with carbodiimide followed by cross-linking more lipase to the amino groups with glutaraldehyde. Immobilization effect and hydrolysis ability in different immobilized conditions of lipase were studied, different factors that influenced the immobilization were investigated, and the optimum conditions were ascertained. Comparative studies of organic solvent, thermal stability and operational stability between free lipase and immobilized lipase were conducted. The immobilization lipase can be reused in the synthesis system of palmitate hexadecyl. After16consecutive batches, the conversion remained85%.Candida sp.99-125lipase was entrapped by drop-wise addition of an aqueous mixture of sodium alginate and the biocatalyst to a hardening solution of a Ca2+salt. Lipase fermentation liquid and free lipase powder was entrapped in Ca-alginate gel respectively. Optimum immobilization conditions such as alginate concentration, CaCl2concentration, lipase loading to alginate and immobilization time on immobilized lipase activity and degree of immobilization were investigated, otherwise, microstructure of immobilization lipase were also investigated. Optimum esterification condition of immobilization free lipase powder was performed. Compared to free lipase the thermal stability of immobilized lipase was significantly improved. This immobilized biocatalyst was applied in biodiesel synthesis by transesterification of salad oil with methanol in non-aqueous solvent and solvent free systems. Optimum parameters were investigated. Operational stability of lipase were also studied, in order to prevent lipase from leaking out of the gel beads, beads were coated with D-trehalose and tetramethoxysilane (TMOS). Compared with non-coated beads, improved immobilized lipase showed the higher operation stability, half life of lipase reach to108h, which was prolonged compared with primary. |
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