Effect of Bacillus sp. DU-106 fermentation on Dendrobium officinale polysaccharide: Structure and immunoregulatory activities

Abstract

In this study, a novel lactic acid probiotic named Bacillus sp. DU-106 was introduced to ferment Dendrobium officinale (D. officinale) polysaccharides, and the effects of such process on the structure and immunostimulatory activity of D. officinale polysaccharide were investigated. Three polysaccharides were subsequently purified from unfermented D. officinale stem (UDP-1), fermented D. officinale stem (FDP-1), and polysaccharide in fermented liquid (FLP-1). After fermentation, the average molecular weight (Mw) of FDP-1 increased from 4.92 × 10⁵ Da (UDP-1) to 5.21 × 10⁵ Da. Fermentation increased the proportions of mannose in FDP-1 by 51.38% compared with that in UDP-1. FDP-1 substantially stimulated cell proliferation and nitric oxide and interleukin-1β (IL-1β) production in RAW 264.7 cells. Probiotic fermentation by Bacillus sp. DU-106 could alter monosaccharide composition and Mw and promote immunostimulatory activities of D. officinale polysaccharide, implying the possible application of Bacillus sp. DU-106-fermented D. officinale polysaccharides as auxiliary functional material in immunotherapy.

Keywords: Chemical structure; Dendrobium officinale; Immunostimulatory activity; Lactic-acid producing Bacillus sp. DU-106; Polysaccharides.