Immobilization of aspergillus niger inulinase with carbon nano tubes

The subject of this thesis is to immobilize Aspergillus (ANI) enzyme on carcilated multi-walled carbon nanotubes (c-MWCNT) by covalent bonding method for the application of fructooligosaccharide (FOS) from inulin. ANI was immobilized on c-MWCNT by crosslinker reagent glutaraldehyde by covalent bonding method with 100% binding efficiency and 82.6% activity efficiency. By characterizing free and immobilized ANI, optimum pH, optimum temperature, pH stability, thermal stability and Michaelis-Menten Constants (Km and Vmax) were determined. While immobilization did not change the optimum pH range (5.5-6.5) and optimum temperature range (55-65 oC) of the enzyme, it increased the pH stability and thermal stability of the enzyme. It was observed that the immobilized enzyme had higher activity and stability than the free enzyme at low and high pH ranges. Immobilization reduced the enzyme's maximum rate and affinity for inulin as a substrate. The maximum velocity (Vmax) obtained for free and immobilized enzymes was 671.1 μmol/mg.min and 568.2 μmol/mg.min, respectively, and the Km constant was determined as 662.3 g/L and 699.3 g/L, respectively. As the Km increases, the affinity of the enzyme for the substrate decreases. The immobilized enzyme maintained its initial activity under optimum activity conditions for 30 consecutive uses. The immobilized enzyme retained its initial activity for 20 days under optimum storage conditions (stored in a 0.1 M sodium phosphate buffer solution with pH 6.0 at +4 °C in the refrigerator) until next use. Using immobilized enzyme, FOS syrup was obtained at 546.9 g/L concentration from 600 g/L of inulin solution with 91.15% conversion rate. As a result, it can be said that the immobilized enzyme obtained in this study can be used industrially in the production of FOS from inulin.