The Effects of Nano Zinc Oxide Shape on Optical Characteristics of Tapioca Starch Films and In Vitro Escherichia coli Microbial Growth Kinetics

This study aimed to investigate the effects of zinc oxide nanoparticle shape on the optical characteristics of tapioca starch films and the microbial growth kinetics of Escherichia coli. For this purpose, nanorods, nano-spheres, and nanoparticles of ZnO at 0.5, 1.0, and 2.0% levels were incorporated into the tapioca starch film solution by solvent casting method. The results showed that tapioca starch-based films were colorless, and by adding different morphology of ZnO nanoparticles and increasing nanoparticles concentrations, the lightness and transparency of the films decreased, and a*, b* and ΔE increased significantly (p<0.05). The bionanocomposite films containing nano-ZnO represented antibacterial activity against E. coli. Their action was directly related to their concentration. With increasing the nano-ZnO concentration, the antibacterial activity increased, and the microbial growth kinetics tended downward. The morphology of nano-ZnO had a remarkable effect on their antibacterial activity, so the highest activity was related to ZnO nano-spheres.