A Human Gut Commensal Ferments Cranberry Carbohydrates To Produce Formate

• Published in: Applied and environmental microbiology Vol. 83; no. 17
• Main Authors: Özcan, Ezgi, Sun, Jiadong, Rowley, David C, Sela, David A
• Format: Journal Article
• Language: English
• Published: United States American Society for Microbiology 01.09.2017
• Subjects: ABC transporter; Acetic acid; Arabinofuranosidase; Bacteria; Berries; Bifidobacterium longum; Biodegradation; Carbohydrates; Digestive system; Fermentation; Food Microbiology; Gastrointestinal tract; Hexose; L-Arabinofuranosidase; Lactic acid; Membrane proteins; Metabolism; Organic chemicals; Polysaccharides; Protein folding; Protein transport; Proteins; Spotlight; Xyloglucan; Xylosidase; prebiotics; food microbiology; bifidobacteria
• ISSN: 0099-2240; 1098-5336
• DOI: 10.1128/aem.01097-17

Commensal bifidobacteria colonize the human gastrointestinal tract and catabolize glycans that are impervious to host digestion. Accordingly, typically secretes acetate and lactate as fermentative end products. This study tested the hypothesis that utilizes cranberry-derived xyloglucans in a strain-dependent manner. Interestingly, the strain that efficiently utilizes cranberry xyloglucans secretes 2.0 to 2.5 mol of acetate-lactate. The 1.5 acetate:lactate ratio theoretical yield obtained in hexose fermentations shifts during xyloglucan metabolism. Accordingly, this metabolic shift is characterized by increased acetate and formate production at the expense of lactate. α-l-Arabinofuranosidase, an arabinan endo-1,5-α-l-arabinosidase, and a β-xylosidase with a carbohydrate substrate-binding protein and carbohydrate ABC transporter membrane proteins are upregulated (>2-fold change), which suggests carbon flux through this catabolic pathway. Finally, syntrophic interactions occurred with strains that utilize carbohydrate products derived from initial degradation from heterologous bacteria. This was a study of bacterial metabolism of complex cranberry carbohydrates termed xyloglucans that are likely not digested prior to reaching the colon. This is significant, as bifidobacteria interact with this dietary compound to potentially impact human host health through energy and metabolite production by utilizing these substrates. Specific bacterial strains utilize cranberry xyloglucans as a nutritive source, indicating unknown mechanisms that are not universal in bifidobacteria. In addition, xyloglucan metabolism proceeds by using an alternative pathway that could lead to further research to investigate mechanisms underlying this interaction. Finally, we observed cross-feeding between bacteria in which one strain degrades the cranberry xyloglucan to make it available to a second strain. Similar nutritive strategies are known to occur within the gut. In aggregate, this study may lead to novel foods or supplements used to impact human health through rational manipulation of the human microbiome.