Optimal conditions for levan biopolymer production and its use in the synthesis of bactericidal levan-ZnO nanocomposite

With the ever-increasing resistance of pathogens to various antibiotics, it has become critically important to find novel biocompatible antibacterial agents. This research focuses on the optimization of the biological synthesis of levan biopolymer using the Taguchi method in order to produce levan-ZnO nanocomposite. Attempts have been made to synthesize this nanocomposite to improve the antibacterial activity of ZnO nanoparticles. Optimization of growth conditions led to the improved levan-producing capabilities of the Zymomonas mobilis PTCC 1718 strain (57 g/l). Molten salt and in situ methods were applied for the synthesis of ZnO nanoparticles and levan-ZnO nanocomposite, respectively. Ultraviolet-visible (UV-vis) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, and scanning electron microscopy (SEM) confirmed the formation of levan biopolymer, ZnO nanoparticles, and levan-ZnO nanocomposite. Antibacterial analysis showed that the formation of nanocomposite improved the antibacterial activity of ZnO nanoparticles. The present study has demonstrated that levan-ZnO nanocomposite characterized by the capability to destroy Gram-positive and Gram-negative microorganisms might be utilized as an antibacterial agent in the medical, pharmaceutical, dentistry, and food industries.