(P09-004-24) Microbial Xylanase Promotes Dietary Xylan Hydrolysis Under Simulated Gastrointestinal Conditions In Vitro: Beyond Galactan- and Fructan-Type FODMAPs

Objectives: Gastrointestinal (GI) sensitivity to fructan- and galactan-type fermentable oligo-, di-, monosaccharides and polyols (FODMAPs) has been described. Less is known about human GI tolerance to plant xylans—polysaccharides comprised of the pentose sugar xylose. Xylans are resistant to human digestive enzymes, yet fermentable by gut microbes. The objective of this study was to test the effects of a food-grade microbial xylanase from Trichoderma longibrachiatum on hydrolyzing xylans from dietary substrates in the INFOGEST static simulation of GI digestion.

Methods: INFOGEST simulations included a 2-min oral phase with porcine amylase, 120-min gastric phase with porcine pepsin, and 120-min intestinal phase with porcine pancreatin. Free xylose concentrations of gastric and intestinal digestas were measured by HPLC to determine xylolytic activity. All simulations were performed in triplicate, and data are reported in mg xylose per g substrate. Substrates included a prebiotic xylooligosaccharide supplement (XOS), cooked brown rice (CBR), and the beechwood xylan (BX) substrate used to determine xylanase activity units (XU) according to an industry-standard assay.

Results: Using BX or XOS in a modified XU assay, xylanase showed activity across a wide pH range and optimally at pH 5.3, suggesting activity in both gastric and intestinal phases. In simulated digestions of XOS, treatment with 8 escalating doses of xylanase (125–16,000 XU) showed significant increases in gastric digesta xylose concentrations starting at 250 XU compared to control (all P < 0.013), up to a 4.7-fold increase at the 16,000 XU dose (31.6 vs. 6.8 mg/g, P < 0.001). Compared to gastric digestas, intestinal digesta xylose concentrations were ~2-fold higher. Simulated digestion of CBR showed significant increases in gastric digesta xylose concentrations at 1,000 XU and above compared to control (all P < 0.012), up to a 62.3% increase at 16,000 XU (26.9 vs. 16.6 mg/g, P < 0.001). Intestinal digesta xylose concentrations following CBR digestion showed significant increases at all doses tested (all P < 0.001), up to an 85.9% increase at 16,000 XU (32.6 vs. 17.6 mg/g,  P < 0.001).

Conclusions: These data demonstrate effective xylolytic activity of microbial xylanase under physiologic GI conditions in vitro and warrant further investigation in the context of FODMAP sensitivity.

Funding Sources: BIO-CAT, Inc