Forming nanoparticles of α-amylase and embedding them into solid surfaces

In the current work nanoparticles (NPs) of α-amylase were generated in an aqueous solution using high-intensity ultrasound, and were subsequently immobilized on polyethylene (PE) films, or polycarbonate (PC) plates, or on microscope glass slides. The α-amylase NPs coated on the solid surfaces have been characterized by ESEM, TEM, FTIR, XPS and AFM. The substrates immobilized with α-amylase were used for hydrolyzing soluble potato starch to maltose. The amount of enzyme introduced in the substrates, leaching properties, and the catalytic activity of the immobilized enzyme were compared. The catalytic activity of the amylase deposited on the three solid surfaces was compared to that of the same amount of free enzyme at different pHs and temperatures. α-Amylase coated on PE showed the best catalytic activity in all the examined parameters when compared to native amylase, especially at high temperatures. When immobilized on glass, α-amylase showed better activity than the native enzyme over all pH and temperature values studied. However, the immobilization on PC did not improve the enzyme activity at any pH and any temperature compared to the free amylase. The kinetic parameters, Km and Vmax were also calculated. The amylase coated PE showed the most favorable kinetic parameters (Km = 5 g L−1 and Vmax = 5E−07 mol mL−1 min−1). In contrast, the anchored enzyme-PC exhibited unfavorable kinetic parameters (Km = 16 g L−1, Vmax = 4.2E−07 mol mL−1 min−1). The corresponding values for amylase-glass were Km = 7 g L−1, Vmax = 1.8E−07 mol mL−1 min−1, relative to those obtained for the free enzyme (Km = 6.6 g L−1, Vmax = 3.3E−07 mol mL−1 min−1).