Evaluation on prebiotic properties of β-glucan and oligo-β-glucan from mushrooms by human fecal microbiota in fecal batch culture

Abstract

Background: β-glucan is dietary fiber, a structural polysaccharide, β-linked linear chains of D-glucose polymers with variable frequency of branches. β-glucan is isolated from different sources such as cell walls of baker’s yeast (Saccharomyces cerevisiae), cereals (oat and barley) and various species of mushrooms. Among 8 mushrooms in the study, Schizophylum commune Fr and Auricularia auricula Judae had the highest in β-glucan contents and the cheapest cost of mushroom per content of β-glucan, respectively. Even the function of β-glucan on immune modulation has been known however no report on interaction between β-glucan and human gut microbiota. Gut microbiota is thought to have health effects by interaction with non-digestible component particular fermentable dietary fiber. It is important to correlate the specific groups of the microbial communities associated with β-glucan fermentation and the consequential SCFA profiles. β-glucan from mushroom may has potential prebiotic function similar to those from commercial yeast (Saccharomyces cerevisiae) β-glucan. Objective: To evaluate on prebiotic properties of soluble β-glucans and oligo-β-glucans from Schizophylum commune Fr and Auricularia auricula Judae by fecal fermentation in batch culture. Methods: In vitro fecal fermentation in anaerobic batch cultures under simulated conditions similar to human colon with human faecal samples from three donors were performed. Comparison on 3 β-glucans and 2 oligo-β-glucans have been studied. Sample was taken at 0 h, 24 h and 48 h to analyze the numbers of bacterial changes by fluorescent in situ hybridization (FISH) technique. Short chain fatty acids (SCFA) were analyzed by HPLC. The prebiotic index (PI) was calculated according to the change of 5 specific bacterial genus within 48 h fermentation. Results: Soluble β-glucan from Auricularia auricula Judae increased numbers of bifidobacteria and lactobacillus significantly (P<0.05). The PI of soluble β-glucan and oligo-β-glucan from Schizophylum commune Fr were 0.01 and -0.01, respectively. β-glucan and oligo-β-glucan from Auricularia auricula Judae were 0.11 and -0.07, respectively. Whereas PI of β-glucan from commercial yeast (Saccharomyces cerevisiae) was 0.03. Acetate was the most prevalent SCFA found in all treatments followed by propionate, butyrate and lactate, respectively. Conclusion: The study confirmed that β-glucan from Schizophylum commune Fr and Auricularia auricula Judae are candidate prebiotics. Keywords: β-glucan, oligo-β-glucan, prebiotic, mushroom, fecal batch culture