Reversible immobilization of glycoamylase by a variety of Cu2+-chelated membranes

Abstract

Glycoamylase (AMG) is an γ-amylase enzyme which catalyzes the breakdown of large α(1,4)-linked malto-oligosaccharides to glucose. It is an extracellular enzyme and is excreted to the culture medium. In this study, AMG was immobilized on a variety of metal affinity membranes, which were prepared by chelating Cu2+ ions onto poly(hydroxyethyl methacrylate) (PHEMA) using N-methacryloyl-(L)-histidine methyl ester (MAH), N-methacryloyl-(L)-cysteine methyl ester (MAC), and N-methacryloyl-(L)-phenylalanine methyl ester (MAPA) as metal-chelating comonomers for reversible immobilization of AMG. The PHEMAH, PHEMAC, PHEMAPA membranes were synthesized by UV-initiated photo-polymerization and Cu2+ ions were chelated on the membrane surfaces. Cu2+-chelated membranes were characterized by swelling tests, SEM, contact angle measurements, elemental analysis, and FTIR. AMG immobilization on the Cu2+-chelated membranes was performed by using aqueous solutions of different amounts of AMG at different pH values and Cu2+ loadings. Durability tests concerning desorption of AMG and reusability of the Cu2+-chelated membranes yielded acceptable results. It was computationally determined that AMG possesses four likely Cu2+/Zn2+ binding sites, away from the catalytic site, to which the metal-chelated membranes can be efficiently used. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012