Insoluble Biopolymer Based Metal Oxide Nanocomposites as Matrix for Enzyme Immobilization

Abstract

Microbial α-amylase obtained as a result of screening of Bacillus subtilis strains can improve the breakdown of heavier biopolymers into simple sugar units. Insoluble chitosan-MnO₂ (CH-MnO_2, S1) and chitosan-NiO (CH-NiO, S2) nanocomposites were synthesised as a matrix for the adsorption of α-amylase and facilitate industrial applications. The physico-chemical characterizations of the synthesised nanocomposites were successfully determined. The optimization of immobilization criteria’s such as pH, temperature, contact time and concentration were noticed using Lowry’s method. The comparison of efficiency of free enzyme with immobilized enzyme were carried out by finding out the activity using DNS method followed by the determination of properties of free enzyme and immobilized enzyme. The rate of activity of free and immobilized enzymes were compared on the basis on activity temperature relationship. The kinetic studies revealed that supports S1 and S2 showed higher K_m and lower V_m values in comparison with free enzyme. The obtained values for K_m and V_m for S1 and S2 are 1.6303 mg/mL, 54 μmolmg^-1min^-1 and 1.2947 mg/mL, 44.8 μmolmg^-1min^-1 respectively. Thermal stability studies showed that S1 and S2 can withstand maximum relative activity upto 65 ^ᵒC respectively. The reusability of the immobilized enzymes S1 and S2 showed maximum retainity in relative activity after 8 cycles. Storage stability of immobilized enzymes S1 and S2 were checked weekly and observed good stability upto 56 % for S1 and 66 % for S2 respectively after 6 weeks. The immobilization efficiency calculated for S1 and S2 were 56 % and 82.5 % respectively. The obtained results arrived at a conclusion of having better immobilization efficiency of support S2 over S1.