Enhanced production and immunomodulatory activity of levan from the acetic acid bacterium, Tanticharoenia sakaeratensis

Abstract

Levan is a fructose polymer with β-(2 → 6) glycosidic linkages. It is produced by several microorganisms, and due to its potential biotechnological and industrial applications, various levan-producing bacteria with different levels of production efficiencies have been reported. We investigated the levan-producing ability of the acetic acid bacterium, Tanticharoenia sakaeratensis. The exopolysaccharides produced by the bacterium under a sucrose environment were characterized as levan by FT-IR, and ¹H and ¹³C NMR. The molecular weight of levan thus produced range from 1.0 × 10⁵-6.8 × 10⁵ Da. The maximum yield of levan from T. sakaeratensis is 24.7 g·L^-1 in a liquid medium containing 20% (w/v) sucrose and incubated at 37 °C, 250 RPM for 35 h. The levan produced by T. sakaeratensis can promote nitric oxide production in RAW264.7 macrophage cells in a concentration-dependent manner, suggesting it has immunomodulatory effects. Our study reveals that T. sakaeratensis can be potentially employed as a new source of levan for industrial applications.

Keywords: Acetic acid bacteria; Exopolysaccharides; Levan; Tanticharoenia sakaeratensis.