Magnetic immobilization and characterization of α-amylase as nanobiocatalyst for hydrolysis of sweet potato starch

• Fungal α-amylase was effectively immobilized on to magnetic nanoparticles.
• The porous surface of nanocomposite enhanced the catalytic activity of α-amylase.
• The strong primary amine group in magnetic nanobiocomposite confirms the presence of α-amylase.
• The affinity of magnetically immobilized α-amylase toward sweet potato starch was found high.

Magnetic immobilization of enzymes became emerging method for efficient recovery of biocatalyst under magnetic field. Sweet potato (Ipomoea batatas) root starch is abundantly produced in tropical countries. Thus the present work was focused on immobilizing α-amylase on to magnetic nanoparticles and use as biocatalyst for hydrolysis of sweet potato starch into glucose. The hydrolysis of sweet potato starch using immobilized α-amylase was investigated and the maximum glucose yield of 42.89 mg/g was obtained using 3% (w/v) of sweet potato starch concentration with an initial pH 4 at 40 °C in 80 min reaction time. The optimal concentration of immobilized α-amylase for maximum glucose yield was found as 1% (w/v). The kinetics of hydrolysis reaction was studied using Michaelis–Menten equation. The sweet potato starch was found to have more affinity towards magnetically immobilized α-amylase with substrate affinity constant (Km) of 0.16 mg/ml and the maximum reaction rate (Vmax) of 3.63 × 10−3 μmol/ml s. The magnetically immobilized nanocomposite of α-amylase can be easily recovered and reused for maximum utilization.