Microbial levan biopolymer production and its use for the synthesis of an antibacterial iron(II,III) oxide-levan nanocomposite

Levan biopolymer is an exopolysaccharide characterized with biocompatibility and unique properties that is widely used in different industries. In this study, this biopolymer was used to synthesize a nanocomposite containing magnetic nanoparticles of iron with antibacterial effects. The effects of three factors at three levels of sucrose (5, 7, and 9 g), KH2PO4 (0.3, 0.5, and 0.7 g), and soy flour (3, 5, and 7 g) were evaluated to produce levan exopolysaccharide by Bacillus polymyxa PTCC1020. Nine experiments were designed with different environmental conditions via the Taguchi method. The nanoparticles of iron oxide were synthesized with the coprecipitation method. In addition, nanocomposites containing magnetic nanoparticles of iron and levan biopolymer were produced. The highest level of levan extraction was observed with conditions of 5 g of soy flour (second level), 0.7 g of KH2PO4 (third level), and 5 g of sucrose (first level) as 27 g/L. The Fourier transform infrared analysis and ultraviolet-visible spectroscopy showed the formation of nanocomposites containing magnetic particles of iron. The results indicate that the synthesized nanocomposites had antibacterial effects on both Escherichia coli and Staphylococcus aureus. We concluded that levan and Fe3O4 could be used to synthesize antibacterial nanocomposites with high potential for various industrial applications. (C) 2016 Wiley Periodicals, Inc.