Physicochemical and biological properties of longan pulp polysaccharides modified by Lactobacillus fermentum fermentation

Longan polysaccharides are valuable compounds with many biological activities. Lactobacillus fermentum was selected to ferment longan pulp and the polysaccharides from unfermented and fermented longan pulp (denoted as LP and LP-F, respectively) were isolated. Their physicochemical, immunomodulatory and prebiotic activities were investigated. The results revealed that LP-F, the molecular weight of which was lower than that of LP, contained less neutral sugar, uronic acid and glucose but more arabinose, galactose, rhamnose and mannose. Compared with LP, LP-F had better solubility, lower apparent viscosity and particle size. LP-F exhibited stronger stimulation on macrophages secretion of NO and IL-6, as well as better proliferation of Leuconostoc mesenteroides and Lactobacillus casei. In summary, fermentation treatment could change the physicochemical properties and enhance the bioactivity of polysaccharides from longan pulp.