Fungal β-glucan-facilitated cross-feeding activities between Bacteroides and Bifidobacterium species

The human gut microbiota (HGM) is comprised of a very complex network of microorganisms, which interact with the host thereby impacting on host health and well-being. beta-glucan has been established as a dietary polysaccharide supporting growth of particular gut-associated bacteria, including members of the genera Bacteroides and Bifidobacterium, the latter considered to represent beneficial or probiotic bacteria. However, the exact mechanism underpinning beta-glucan metabolism by gut commensals is not fully understood. We show that mycoprotein represents an excellent source for beta-glucan, which is consumed by certain Bacteroides species as primary degraders, such as Bacteroides cellulosilyticus WH2. The latter bacterium employs two extracellular, endo-acting enzymes, belonging to glycoside hydrolase families 30 and 157, to degrade mycoprotein-derived beta-glucan, thereby releasing oligosaccharides into the growth medium. These released oligosaccharides can in turn be utilized by other gut microbes, such as Bifidobacterium and Lactiplantibacillus, which thus act as secondary degraders. We used a cross-feeding approach to track how both species are able to grow in co-culture. ss-glucans, potential prebiotic fibers derived from mycoprotein, can be degraded by human gut Bacteroides via extracellular glycoside hydrolases; produced oligosaccharides can in turn feed Bifidobacterium species as shown by a cross-feeding approach.

Automated summary

The human gut microbiota (HGM) is a complex network of microorganisms that interact with the host and impact host health. Beta-glucan, a dietary polysaccharide, supports the growth of specific gut bacteria, including Bacteroides and Bifidobacterium. However, the mechanism of beta-glucan metabolism by gut commensals is not fully understood. This study shows that certain Bacteroides species degrade mycoprotein-derived beta-glucan, releasing oligosaccharides that can be utilized by other gut microbes such as Bifidobacterium.