Gut microbial utilization of xylan and its implication in gut homeostasis and metabolic response

Xylan as the second most abundant indigestible carbohydrate found in nature attracts great interests of researchers, nutritionist and consumers due to its various health benefits. However, accumulated studies indicate the interactions with gut microbiota greatly affect these benefits, and significant progress has been made over the past few years to understand how microbes utilize xylan at gene level. In this review, we focused on gut xylanolytic microbes and xylan's physico-chemical features, summarized the xylanases needed for complete xylan decomposition, their substrate specificity and the presence in gut microbes, as well as microbial degradation of xylan in single strain mode and cooperation mode. Xylan utilization system were discussed with different phyla. Furthermore, the implications on intestinal homeostasis and metabolic response were reviewed with clinical effects emphasized, and highlight is placed on specific gut microbes and the complexity of xylan structure to provide a clue for the inconsistent results in human studies. CHEMICAL COMPOUNDS: xylan; arabinoxylan, glucuronoxylans; glucuronoarabinoxylans; xylo-oligosaccharides; arabinoxylo-oligosaccharides.