GH11 xylanase increases prebiotic oligosaccharides from wheat bran favouring butyrate-producing bacteria in vitro

Abstract

Alternative solutions to optimise intestinal health in monogastric animals have become essential since the ban of antimicrobials in animal feed. In this study, the prebiotic potential of a commercial feed GH11 xylanase was investigated in vitro. Enzymatic degradation of arabinoxylan (AX), the substrate present in wheat bran cell walls, was visualised using immuno-microscopy techniques. The arabinoxylooligosaccharides (AXOS) generated by the enzyme were analysed by non-starch polysaccharide (NSP) analysis, mass spectrometry (MS) and carbohydrate chromatography to investigate how AXOS glycan complexity and enzyme dosage may affect fermentation patterns in a wheat-based diet. Using a 10mg EP/kg dosage of xylanase, AXOS with an average degree of polymerisation (avDP) of 10 were generated, while using a higher enzyme dosage (50mg EP/kg) avDP shifted to 4–8. For both enzyme concentrations, AXOS had an arabinose/xylose ratio of ∼0.4. Wheat bran incubated without or with xylanase was simultaneously fermented by broiler cecal bacteria in vitro and short chain fatty acid production was monitored. A small (but significant) increase in butyrate production by addition of xylanase was shown to be dose-dependent and increased by 2mM (P<0.05) compared to control by adding 50mg EP/kg enzyme dosage. Butyrate-producing bacterial genera Faecalibacterium and Intestinimonas were significantly increased in fermentation reactions of wheat bran with GH11 xylanase addition while Bacteroidetes levels were significantly lowered. Supernatants from fermentation reactions of wheat bran incubated with and without xylanase and cecal microbiota were tested in an intestinal epithelial layer permeability assay using Caco-2 cells stimulated with LPS. The xylanase addition to the bran incubated with cecal content of broilers reversed LPS-induced epithelial layer resistance losses. The GH11 xylanase was able to solubilise and degrade wheat bran AX to yield low avDP AXOS that can be fermented by cecal microbiota, resulting in microbiota shifts and beneficial effects on transepithelial resistance in vitro.