Possibility of using endo-inulinase with high thermal stability to produce high fructose syrup from inulin

Inulinase with high thermal stability is preferred to hydrolyze inulin and produce high fructose syrup to increase the rate of conversion, prevent microbial contamination and make inulin more soluble. The aim of this study was to evaluate the structural and functional characteristics of endo inulinase after modification with PLP. To determine the thermal stability, the residual activities of the endo inulinase before and after modification with PLP was measured after 130-minute incubation at 25-65°C while, their activities were measured daily to estimate the shelf stability. Circular Dichroism, absorbance in 280 nm, extrinsic and intrinsic fluorescence were carried out to assay the structural changes and the secondary and territory structure of the endo inulinase before and after modification with PLP. Chromatograms of inulin hydrolysis products were plotted after hydrolysis with either native or PLP modified endo-inulinase using HPLC and the catalytic parameters of both enzymes were calculated. α-helix content increased after modification with PLP. The results of assaying the territory structure including UV-vis and fluorescence emissions confirmed the improved thermal stability of endo inulinase after PLP modification. The results of the shelf stability proved the reduced activity loss of PLP modified inulinase, compared to the native one. Efficiency improvement of PLP modified inulinase for inulin hydrolysis was demonstrated by HPLC. After enzyme modification, Vmax increased and Km decreased which proves the improved efficiency of the PLP modified enzyme.