Adsorption of α-amylase and Starch on Porous Zinc Oxide Nanosheet: Biophysical Study

Abstract

Engineered biocatalyst and its desired products using nanotechnology has intensified the research in food industries. Zinc oxide (ZnO) nanosheet is designed and prepared; the characterization studies include surface plasmon resonance peak (364 nm), X-ray diffraction pattern determined crystallite size (25 nm), and transmission electron microscopy confirms the porous surface nature. Atomic force microscopy showed substrate and enzyme adsorbed on ZnO nanosheets. The zeta potential of ZnO nanosheet (−41.9 mV) whereas α-amylase bound with ZnO nanosheets (−32.8 mV), and starch bound with ZnO nanosheets (−28.7 mV) was analyzed using dynamic light scattering. The circular dichroism spectra displayed α-helix in native amylase at optimum concentration 54.70% compared to the adsorbed α-amylase with ZnO nanosheet that showed 37%. Freundlich isotherm model revealed multilayer adsorption behavior of α-amylase onto porous ZnO nanosheet. Enzyme kinetics study presents alteration in Michaelis–Menten constant (Km) and maximum velocity (Vmax), the α-amylase bound with porous ZnO nanosheet showed a reduction in Km and Vmax. The substrate and enzyme adsorbed together on porous ZnO nanosheet exhibited increased Km (27.77 μM), whereas Vmax (2.85 μM) remains unchanged. Moreover, α-amylase once modified at optimum pH (5.8) and temperature (52 °C), produces less maltose than α-amylase adsorbed on ZnO nanosheet, which indicates higher maltose production. In this study, ZnO nanosheet enzyme catalytic system was created, wherein enzymatic reaction shifted to different pH and temperature other than optimum conditions. All these findings suggest that careful attention to the enzyme adsorption profiles can contribute to industrial applications.