Molecular structure features and lactic acid fermentation behaviors of water- and alkali-soluble polysaccharides from Dendrobium officinale

One water-soluble polysaccharide (WDOP) and three alkali-soluble polysaccharides (ADOP1, ADOP2 and ADOP3) were successfully obtained from Dendrobium officinale. Molecular structure of the polysaccharides was analyzed, and in vitro lactic acid fermentation of the polysaccharides by lactic acid bacteria (LAB) and bifidobacteria was performed. All the polysaccharides exerted proliferative effect on the LAB and bifidobacteria. ADOP2 was the most effective one, followed by WDOP. This could be attributed to their molecular structure features, such as a high level of total sugar, uronic acid and reducing sugar, an abundance of glucose and mannose, and a low and middle weight-average molecular weight. ADOP2 and WDOP produced more short-chain fatty acids (SCFAs) than ADOP1 and ADOP3 did during lactic acid fermentation. Propionic and acetic acids were the main SCFAs produced. These findings are useful for understanding the structure–activity relationship of D. officinale polysaccharides in lactic acid fermentation, and for developing new functional foods and beverages from D. officinale.