Exo‐inulinase production from <i>Aspergillus fumigatus</i> NFCCI 2426: purification, characterization, and immobilization for continuous fructose production

Abstract

Abstract Aspergillus fumigatus was found to produce thermostable exo‐inulinase (EC 3.8.1.80; 38 U/ml) on inulin‐rich infusions. Exo‐inulinase (14.6 U/mg) was immobilized on glutaraldehyde activated Ca‐alginate beads for continuous generation of fructose by hydrolyzing sucrose, chicory, and dandelion substrates. Immobilization of enzyme was confirmed by microscopic and spectroscopic techniques. The exo‐inulinase was purified using ion‐exchange (1.30‐folds) and size‐exclusion chromatography (2.71‐folds). The purified exo‐inulinase showed 64 kDa band on gel and was optimally active at 60 °C and pH 6.0. Kinetic constants, K m and V max of purified exo‐inulinase, were 5.88 mM and 1.66 µM/min, respectively, and its relative activity was found to be enhanced (125.8%) in the presence of calcium ion. Immobilized preparation was utilized for continuous generation of fructose from chicory juice (26 to 70%) and dandelion root extracts (16 to 24%) by recycling upto five cycles, respectively. In comparison to other sweeteners, such as sucrose, fructose is considered as a healthy alternative. The present study demonstrated the use of immobilized exo‐inulinase in continuous generation of fructose from some underutilized plant sources that can be used in food industry. Practical Application Thermostable exo‐inulinase produced by A. fumigatus was immobilized on calcium alginate matrix and was employed for continuous hydrolysis of chicory juice and dandelion root extract for generation of fructose syrup.