Production and characterization of levans with different molecular weights synthesized by Bacillus licheniformis ZM107.

Levan, a fructan-type polysaccharide with diverse applications in food, pharmaceuticals, and biotechnology, has garnered significant attention for its functional properties, such as prebiotic, immunomodulatory, antioxidant, and antimicrobial activities. In this study, the effects of fermentation temperature, sucrose concentration, and incubation time on the molecular weight of levan produced by Bacillus licheniformis fermentation were investigated. The results showed that as the temperature (37°C-50°C) and sucrose concentration (300-500 g l-1) increased, the molecular weight of levan produced by the strain during fermentation decreased. At the same time, the molecular weight initially increased and then decreased with longer culture times, indicating that levan within a specific size range could be produced by controlling the fermentation conditions. In addition, the properties and characteristics of levan produced by fermentation at two molecular weights (HML and LML) were compared. The results showed that molecular weight significantly affected the micromorphology, thermal behavior, rheological properties, and prebiotic activity of levan. Therefore, this study demonstrated that Bacillus licheniformis SFLV-ZM107 can produce low molecular weight levan, and its molecular weight can be controlled through fermentation conditions. Consequently, the properties and functions of levan can be influenced, allowing the production of levans with the desired characteristics.