Lipase from Mucor miehei was covalently immobilised onto a graft copolymer with a backbone of polyethylene and side chains of poly(hydroxyethylmethacrylate), partially hydrolysed (PE-g.co-HEMA). This support was designed to have a controlled surface hydrophilicity, to modulate the lipase microenvironment in organic medium. The synthesis of n-octyl oleate in the absence of solvents was used as a model reaction. The functional copolymer has a larger affinity to lipase than to other proteins in the crude lipolytic extract. On the basis of the same volume of crude lipase used in both free and immobilised forms, esterification activity immobilisation yields as large as 500% were obtained. Operational stability under strong stirring conditions compared favourably with lipase immobilised onto other supports. Shelf stability of this new catalytic material, dehydrated and kept in fridge, showed no appreciable decrease after one year of storage. A greater specific activity of lipase after immobilisation, the purification effect of this process and the operational and shelf stability are mainly attributed to properties of support copolymer.
展开▼
