Abstract
The biopolymer levan has sparked a lot of interest in commercial production and various industrial applications. In this study, a bacterial isolate with promising levan-producing ability was isolated from a soil sample obtained from Princess Nourah bint Abdulrahman University in Saudi Arabia. The isolate has been identified and submitted to GenBank as Bacillus subtilis MZ292983.1. The bacterial levan polymer was extracted using ethyl alcohol (75%) and CaCl2 (1%) and then characterized using several approaches, such as Fourier transform infrared spectrometry and nuclear magnetic resonance. The IR spectrum of the levan polymer showed characteristic peaks confirming characteristics of polysaccharides, including a broad stretching peak of OH around 3417 cm(-1) and aliphatic CH stretching was observed as two peaks at 2943, and 2885 cm(-1). In addition, the FTIR spectrum featured an absorption at 2121 cm(-1), indicating the fingerprint of the beta-glycosidic bond. Based on H-1 and C-13 NMR spectroscopy analysis, six unexchanged proton signals related to fructose as a forming monomer of levan were observed. Evaluation of levan's antibacterial effect against two pathogenic bacteria, S. aureus (ATCC 33592) and E. coli (ATCC 25922), showed inhibition zones of 1 cm and 0.8 cm in diameter, respectively, with MICs of more than 256 mu g mL(-1) for both strains. Moreover, the antibiofilm property of the levan polymer was assessed and the results showed that the inhibition rate was positively proportional to the levan concentration, as the inhibition percentages were 50%, 29.4%, 29.4%, 26.5%, and 14.7% at concentrations of 2, 1, 0.5, 0.25, and 0.125 mg mL(-1), respectively. Levan showed a significant role in burn healing properties since it accelerated the process of healing burn-induced areas in rats when compared with those either treated with normal saline or treated with the cream base only.