Immobilization of yeast alcohol dehydrogenase by entrapment and covalent binding to polymeric supports

Yeast alcohol dehydrogenase (YADH), which catalyzes oxidoreductions of a broad spectrum of substrates, was immobilized by entrapping it into a network of a poly(acrylamide-co-hydroxyethyl methacrylate) copolymer and was also covalently bound onto porous chitosan beads activated through glutaraldehyde. Maximum retention of YADH activity achieved was 90 and 24% for entrapment and covalent binding, respectively. The results obtained for thermal, storage, and operational stability of entrapped and covalently bound YADH were compared with free YADH. The immobilized enzyme showed improved thermal and storage stability. The immobilized enzymes also retained 50% activity after six and eight cycles. Enzyme-catalyzed oxidation of ethanol was observed to be diffusion-controlled through Lineweaver-Burk plots. (C) 2001 John Wiley & Sons, Inc.