Fabrication of a soluble crosslinked corn bran arabinoxylan matrix supports a shift to butyrogenic gut bacteria
Insoluble fermentable cell wall matrix fibers have been shown to support beneficial butyrogenic gut Clostridia, but have restricted use in food products. Here, a soluble fiber matrix was developed that exhibited a similar effect. A low arabinose/xylose ratio corn bran arabinoxylan (CAX) was extracted with two concentrations of sodium hydroxide, 0.25 M and 1.5 M, to give soluble polymers with relatively low (L) and high (H) residual levels of bound ferulic acid (FA) (CAX-LFA and CAX-HFA). After laccase treatment to make diferulate crosslinks, soluble matrices were formed with average 3.5 to 4.5 mer. In vitro human fecal fermentation of CAX-LFA, CAX-HFA, soluble crosslinked ∼3.5 mer CAX-LFA (SCCAX-LFA), and ∼4.5 mer SCCAX-HFA revealed that the SCCAX matrices had somewhat slower fermentation properties by measuring the gas production, total short chain fatty acids, and carbohydrate disappearance, with a higher butyrate proportion in SCCAX-HFA. 16S rRNA gene sequencing showed that SCCAX-HFA promoted OTUs associated with butyrate production including unassigned Ruminococcaceae, unassigned Blautia, Fecalibacterium prausnitzii, and unassigned Clostridium. Thus, when the physical form of an individual soluble polysaccharide was changed to a soluble crosslinked matrix, in vitro fermentation was shifted to Clostridial butyrate producers. This study shows that the physical form of the fiber influences the competition for substrate among the gut bacteria. Crosslinking of soluble fibers may be a strategy for developing soluble matrices with good physical functionalities for beverages and other foods to improve gut health.