Immobilisation of α-amylase from Aspergillus niger onto polyaniline

α-Amylase from Aspergillus niger culture medium was immobilised on glutaraldehyde-modified polyaniline (PANIG-AMY) in a yield of 42% activity retention. Compared with the free enzyme, PANIG-AMY was less sensitive to inhibition by Zn2+, Cu2+ and Fe2+. The catalytic efficiencies of hydrolysis of starch (potato, cassava, wheat, maize and rice/maize) were similar for free and PANIG-AMY. Oligosaccharides were formed following the hydrolysis of potato starch by PANIG-AMY whereas the free enzyme produced oligosaccharides and glucose. PANIG-AMY retained 50% of its activity after repeated assay and storage at 5 °C and pH 7.0. The thermal stability of PANIG-AMY was increased by the presence of CaCl2. The repeated batch-wise hydrolysis of potato starch using 5.0 mg of PANIG-AMY (0.8 U α-amylase) produced 1.7 μmol of reducing sugar per cycle, yielding a total of 25.5 μmol of reducing sugar after 15 cycles. The same yield would require 12.5 U of free α-amylase.