Catalytic characteristics and application of l-asparaginase immobilized on aluminum oxide pellets.

l-asparaginase from Escherichia coli (l-ASNase) was covalently immobilized on aluminum oxide pellets (AlOPs) using a cross-linking agent, glutaraldehyde. Maximum immobilization yield (85.0%) was obtained after optimizing immobilization parameters using response surface methodology (RSM). Both free and immobilized l-ASNase (AlOP-ASNase) were optimally active at 37°C and pH7.5. However, the bioconjugate exhibited enhanced activity and stability at different pH and temperatures. It had higher affinity (low Km) and was comparatively more stable in presence of some solvents (ethyl acetate, acetone, acetonitrile), metal ions (Ag+, Zn2+) and β-mercaptoethanol. AlOP-ASNase was reused in a glass column reactor for l-asparagine hydrolysis upto nine successive cycles without any loss in activity. The AlOP-ASNase was effective in lowering l-asparagine level in blanched potato chips indicating its potential use in mitigating acrylamide formation in starchy foods. This cost-effective enzyme preparation had shelf-life of more than 30days and can be effectively used in starch based food industries.