Inulinase from Rhodotorula mucilaginosa: immobilization and application in the production of fructooligosaccharides

Abstract

The crude extract containing inulinase from Rhodotorula mucilaginosa was obtained by submerged fermentation. Inulinase was immobilized on chicken eggshell by physical adsorption and covalent crosslinking, using glutaraldehyde as a crosslinking reagent, and Celite by adsorption. Fructooligosaccharides production was performed using immobilized inulinase (5%, w/v) and inulin substrate solution under experimental conditions evaluated through Doehlert experimental design. The production of inulinase was optimized for concentrations of D-glucose and yeast extract at 12.5 and 0.5g/L, respectively, resulting in an optimal activity of 0.62 U. The optimal pH and temperature for enzyme activity were 8.0 and 75°C, respectively, leading to an optimal activity of 3.54 U. The highest immobilization efficiency (46.27%) was obtained upon immobilization on Celite. Immobilization by adsorption to eggshell allowed for specific activity of 4.15 U/g, and adsorption to Celite resulted in specific activity of 3.70 U/g. The highest titer in fructooligosaccharides was obtained with an initial inulin concentration of 250g/L (25%, w/v), and a reaction time of 16h. Hence, immobilized inulinase proved to be a promising catalyst for fructooligosaccharides production since the formulation is performed through a simple, low-cost, and large-scale applicable methodology.