Macromolecular cross-linked enzyme aggregates (M-CLEAs) of α-amylase

Macromolecular cross-linked enzyme aggregates (M-CLEAs) of alpha-amylase were prepared by precipitation and subsequent cross-linking. The non-toxic, biodegradable, biocompatible, renewable polysaccharide based macromolecular cross-linkers viz. agar, chitosan, dextran, and gum arabic were used as a substitute for traditional glutaraldehyde to augment activity recovery toward macromolecular substrate. Macro molecular cross-linkers were prepared by periodate mediated controlled oxidation of polysaccharides. The effects of precipitating agent, concentration and different cross-linkers on activity recovery of a amylase CLEAs were investigated. or-Amylase aggregated with ammonium sulphate and cross-linked by dextran showed 91% activity recovery, whereas glutaraldehyde CLEAs (G-CLEAs) exhibited 42% activity recovery. M-CLEAs exhibited higher thermal stability in correlation with alpha-amylase and G-CLEAs. Moreover, dextran and chitosan M-CLEAs showed same affinity for starch hydrolysis as of free alpha-amylase. The changes in secondary structures revealed the enhancements in structural and conformational rigidity attributed by cross-linkers. Finally, after five consecutive cycles dextran M-CLEAs retained 1.25 times higher initial activity than G-CLEAs. (C) 2015 Elsevier B.V. All rights reserved.