In vitro prebiotic activities of oligosaccharides from the by-products in Ganoderma lucidum spore polysaccharide extraction

Abstract

Until recently, a variety of oligosaccharides from fruits, vegetables and mushrooms have demonstrated positive prebiotic effects. Ganoderma lucidum, a well-known traditional medicine and tonic in East Asia, has been utilized in the prevention and treatment of a broad range of illnesses. In this study, each of three oligosaccharides was obtained from the polysaccharide extraction by-products of sporoderm: the unbroken and broken spores of Ganoderma lucidum (UB-GLS, B-GLS). Their molecular weight distribution, monosaccharide composition and preliminary structures were analyzed using gel permeation chromatography (GPC), GC-MS, UV and FTIR, respectively. All of the oligosaccharides were found to exhibit prebiotic activities, evaluated by detecting growth stimulation on Lactobacillus in vitro. Among these, UB-O80 and B-O80 displayed the most significant effects (p < 0.05) in these groups, and UB-O80 showed higher resistance to hydrolysis by artificial human gastric juice compared with inulin, giving a maximum hydrolysis rate of 1.65%. Compared with inulin media, Lactobacillus also revealed high tolerance to lower pH levels and simulated gastric juices in UB-O80 and B-O80 media. Compared with a control in gut microbiota fermentation, the abundance of some beneficial bacteria increased and some harmful bacteria declined in the groups of UB-O80 and B-O80. In conclusion, the results suggest that GLS oligosaccharides could be exploited as promising prebiotics for the enhancement of human health.

Fig. 1. Molecular weight distributions of different GLS oligosaccharides in GPC profiles: (a) UB-GLS oligosaccharides; (b) B-GLS oligosaccharides.

Fig. 2. FTIR and UV spectra of different GLS oligosaccharides: (a) FTIR spectra of UB-GLS oligosaccharides; (b) FTIR spectra of B-GLS oligosaccharides; (c) UV spectra of UB-GLS and B-GLS oligosaccharides.

Fig. 3. Growth of Lactobacillus (a and b) and changes in sugar concentration (c and d) over fermentation time as supplemented with different carbon sources.

Fig. 4. Resistance of UB-O80 and inulin to various artificial gastric juices: incubation for 6 h at 37 °C.

Fig. 5. Tolerance of Lactobacillus in different carbon sources media containing simulated gastric juice.

Fig. 6. Gut microbiologic community bar chart on family level influenced by GLS oligosaccharides.