Production of levansucrase from novel honey Bacillus subtilis isolates capable of producing antiviral levans

Six Bacillus strains were isolated from different honey sources as levansucrase producers. The isolates were identified as Bacillus sp. based on both phenotypic and molecular identification using sequencing of 16S rRNA gene method. To distinguish them on species level other genes such as recA and ytcP genes have been employed. The molecular identification methods revealed that the six strains K, M, A, C, E, and G belong to unique Bacillus subtilis. Levan production by the isolates was dependent mainly on commercial sucrose media, the use of beet molasses glucose, lactose and fructose led to noticeable reduction in levan synthesis. Chemical hydrolysis of levan products showed that the polysaccharide consisted entirely of fructose. Levan produced by isolates K, M, A, C, E, and G had different molecular masses (40.938, 71.887, 43.487, 154.638, 77.753 and 14.200 kDa, respectively). The levan yield using sucrose medium for isolates M, K, A, C, E and G were 11.00, 16.25, 6.60, 1.81, 1.74, and 6.6 g/L, respectively. The biological activity of levan produced by strains K, M and E had antiviral activity against pathogenic avian influenza HPAI, H5N1 while levan produced by strains A and M had antiviral activity against adenovirus type 40.