Immobilization of inulinase from Aspergillus niger on octadecyl substituted nanoporous silica: Inulin hydrolysis in a continuous mode operation

Abstract

Abstract Inulinase hydrolyzes inulin and produce high fructose syrup in a single-step reaction. However, finding the best working conditions and the highest inulinase stability, especially in continuous mode operations are of critical value. Native (endo-inulinase (EC 3.2.1.7)) and chemically modified inulinases (endo-inulinase stabilized with pyridoxal 5′-phosphate/ascorbic acid in a semi-rational chemical modification approach) were immobilized on octadecyl substituted nanoporous silica (with the average pore size of 66 nm) by using dioxane to extend the hydrophobic interactions between inulinase refolding intermediates and the hydrophobic alkyl moieties of the support. Native and modified inulinases revealed their maximum surface hydrophobicity at 40% and 50% dioxane in water, respectively. Immobilized inulinases (native and modified) showed 7.89 and 3.73 fold increase in their half lives compared to the free native sample., higher reusability compared to free inulinases (native and modified) and also could retain their activities after 10 hydrolysis cycles in a continuous mode of experimental conditions.