Characterization of a novel endo-levanase from Azotobacter chroococcum DSM 2286 and its application for the production of prebiotic fructooligosaccharides.

Prebiotics are known for their ability to modulate the composition of the human microbiome and mediate health-promoting benefits. Endo-levanases, which hydrolyze levan into short-chain FOS, could be used for the production of levan-based prebiotics. The novel endo-levanase (LevB) from Azotobacter chroococcum DSM 2286, combines an exceptionally high specific activity with advantageous hydrolytic properties. Starting from levan isolated from Timothy grass, LevB produced FOS ranging from DP 2 - 8. In contrast to endo-levanases described in the literature, LevB formed minor amounts of fructose and levanbiose, even with greatly extended incubation. The combined activity of LevB and the levansucrase LevS from Gluconobacter japonicus LMG 1417 led to a one-step synthesis of levan-type FOS from sucrose. 387.4 ± 17.3 g L FOS were produced within 48 h by the production strategy based on crude cell extract of recombinant Escherichia coli expressing levS1417 and levB2286 simultaneously.