Effects of additives on the activity of a covalently immobilised lipase inorganic media

Lipase from Mucor miehei was covalently immobilised onto the graft copolyme r poly(ethylene)-g.co-hydroxyethyl methacrylate (EE-g.co-HEMA), partially h ydrolysed, via a spacer arm of 1,6-diaminohexane activated with glutaraldeh yde. To improve the lipolytic activity of the immobilised lipase (for the s ynthesis of isoamyl-caprylate, as a model), the effect of several additives was investigated. Polyethylene glycol (PEG), glutaraldehyde, organic solve nts and buffers, were added during the immobilisation procedure and their e ffects are reported and compared with the behaviour of the lipolytic prepar ation without pre-treatment. An increase of 40-100% in the activity was obt ained when small quantities of PEG 2000 and glutaraldehyde (used also as an activator of the spacer arm) were added. The activity had a maximum when t he pH of the lipase attachment solution was 7.2 and buffered with phosphate . The effect of the aggregation level of biocatalyst particles on the amoun t of water retained, as well as the effect of the immobilisation on solid s upports on the stability to organic solvents, is also reported. (C) 1998 El sevier Science B.V. All rights reserved.