Polyaniline-assisted silver nanoparticles: a novel support for the immobilization of α-amylase.

The size distribution of nanomaterials and their similarity in size with enzyme molecules together with other advantageous properties such as thermal stability, high surface-to-volume ratio, and irradiation resistance have revolutionized nanobiocatalytic approaches in various areas of enzyme technology. In the present study, polyaniline-assisted Ag nanocomposites were synthesized using ammonium peroxydisulfate as oxidant. These nanocomposites were used as a support for the covalent conjugation of α-amylase, one of the important industrial enzymes. X-ray diffraction study showed that the crystalline nature of nanocomposites was increased in the presence of Ag nanoparticles. Thermogravimetric and differential thermal analysis revealed that the synthesized nanocomposites retained significantly very high thermal stability. Scanning electron micrograph showed that Ag nanoparticles were homogeneously dispersed in polyaniline film providing large surface area and microenvironment for enzyme loading. Fourier transform infrared spectroscopy confirmed the conjugation of α-amylase to the functionalized nanocomposites. The conjugated α-amylase exhibited better tolerance to variations in the medium pH and temperature compared with the native enzyme. Immobilized α-amylase hydrolyzes starch more efficiently as compared to the free enzyme in batch process.