Controlling autohydrolysis conditions to produce xylan-derived fibers that modulate gut microbiota responses and metabolic outputs

Authors: ZHAO, SAINAN - Nanyang Technological University; Dien, Bruce; LINDEMANN, STEPHEN - Purdue University; CHEN, MING-HSU - Nanyang Technological University

Submitted to: Carbohydrate Polymers
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/6/2021
Publication Date: 7/9/2021
Citation: Zhao, S., Dien, B.S., Lindemann, S.R., Chen, M. 2021. Controlling autohydrolysis conditions to produce xylan-derived fibers that modulate gut microbiota responses and metabolic outputs. Carbohydrate Polymers. 271. Article 118418. https://doi.org/10.1016/j.carbpol.2021.118418.
DOI: https://doi.org/10.1016/j.carbpol.2021.118418

Interpretive Summary: The human gut is home to numerous bacteria that aidin the digestion of food fiber and also play an important role in maintaining overall health. Soluble fiber often contains a sugar-based product named xylo-oligosaccharides, which reduces the risk for diabetes, improves cholesterols, and guards against chronic inflammation symptoms. ARS researchers are developing these sugar-based products (also referred to as polysaccharides) as a health-promoting food ingredient. In this study, these polysaccharides were produced using various conditions and the products examined for their size and complexity. Bioassay was used to determine their benefit in maintaining the right type of gut bacteria using a state of the art method. In this method, human fecal samples are used to inoculate cultures containing the different polysaccharides and changes in gut bacteria monitored by DNA sequencing of the entire population. Advanced statistics are used to analyze this complex set of data. Results from this study show that the fed products elicited different responses, some of which had better expected outcomes for gut health. This shows that manufacturing conditions are important for determining product quality; in the past, only product yield was a consideration. This study begins to relate product specifications with quality. This study is of broad interest to those studying gut health and because these polysaccharides are derived from crops, to agriculture processors looking to develop better value-added products. It is also expected to promote the rural economy by taking low-cost fiber and converting it into a much sought after food ingredient.

Technical Abstract: Autohydrolysis, a hydrothermal process, is used as a pretreatment and for producing xylan-derived oligosaccharides from the lignocellulosic materials, which are of interest as probiotics. Although numerous studies report optimized autohydrolysis condition for various plants, currently, there is a scarcity of studies correlating the process parameters and the resulting structural properties to their impact on the intestinal bacteria communities. Thus, to further clarify these relationships, beechwood xylan (BWX)-derived substrates, processed under five conditions, were fermented in vitro with the human gut microbiota. Autohydrolysis reduced the mean molecular size and substitutions of BWX. Distinct fermentation kinetics were observed even though there was no difference in the neutral sugar compositions of the BWX. Feeding different BWX substrates altered species evenness. The relative abundances of Bacteroides, Fusicatenibacter, Blautia, Bifidobacterium, and Megasphaera within the populations varied with substrate. While the total short-chain fatty acid concentrations were the same among the treatments, a substrate effect for propionate or butyrate generation was observed. In conclusion, setting autohydrolysis parameters for xylan-derived fiber production can be used to vary the response of human gut microbiota.