(1 → 3),(1 → 6) and (1 → 3)-β-D-glucan physico-chemical features drive their fermentation profile by the human gut...

Area of Science:

• Microbiology
• Biochemistry
• Nutrition Science

Background:

• Mushroom polysaccharides, specifically beta-glucans, reach the human gut intact.
• These polysaccharides can be fermented by gut bacteria, potentially benefiting host health.
• The structural characteristics of beta-glucans influence their fermentation and impact on the gut microbiota.

Purpose of the Study:

• To isolate and characterize beta-glucans from Pholiota nameko and Pleurotus pulmonarius.
• To evaluate the in vitro fermentation profiles of these beta-glucans by human gut microbiota.
• To determine the relationship between beta-glucan structure (solubility, branching) and fermentation outcomes.

Main Methods:

• Extraction and isolation of four (1→3),(1→6)-β-D-glucans from two mushroom species.
• Controlled Smith degradation to obtain linear (1→3)-β-D-glucans.
• In vitro fermentation assays with human gut microbiota to measure short-chain fatty acid (SCFA) production and bacterial population changes.

Main Results:

• The four β-D-glucans varied in water solubility and molar mass (2.2 × 10^5 to 1.9 × 10^6 g.mol⁻¹).
• Fermentation resulted in diverse SCFA production (52.0–97.0 mM/50 mg carbohydrates), with consistent high propionate levels (28.5–30.3%).
• All glucans promoted Bacteroides uniformis; Anaerostipes sp. and Bacteroides ovatus growth depended on glucan solubility and branching.

Conclusions:

• The structural features of mushroom β-D-glucans significantly dictate their fermentation by human gut microbiota.
• Specific glucan structures influence the production of short-chain fatty acids and the abundance of key gut bacteria.
• Understanding these structure-function relationships is crucial for harnessing the prebiotic potential of mushroom polysaccharides for gut health.