Non-starch polysaccharide-degrading enzymes alter the microbial community and the fermentation patterns of barley cultivars and wheat products in an in vitro model of the porcine gastrointestinal tract

An in vitro experiment was carried out to assess how non-starch polysaccharide (NSP)-degrading enzymes influence fermentation of dietary fibre in the pig large intestine. Seven wheat and barley products and cultivars with differing carbohydrate fractions (CHO) were hydrolyzed using pepsin and pancreatin in the presence or not of NSP-degrading enzymes (xylanase and b-glucanase) and the filter retentate fermented with sow fecal bacteria. Dry matter, starch, crude protein and β-glucan digestibilities during hydrolysis were measured. Fermentation kinetics of the hydrolyzed ingredients were modelled. Short-chain fatty acids (SCFA) production and molar ratio were compared after 12, 24 and 72 h. Microbial communities were analyzed after 72 h of fermentation using terminal restriction fragment length polymorphism (TRFLP). The results showed an increase of nutrient digestibility (P<0.001), whereas fermentability and SCFA production decreased (P<0.001) with addition of the enzyme. SCFA and bacterial community profiles indicated also a shift from propionate to acetate and an increase in cellulolytic Ruminoccocus- and xylanolytic Clostridium-like bacteria. This is explained by the increase in slowly fermentable insoluble CHO and the lower proportion of rapidly fermentable β-glucan and starch in the retentate when grains were incubated with NSP-degrading enzymes. Shifts were also different for the 4 barley varieties investigated, showing that the efficiency of the enzymes depends on the structure of the CHO fractions in cereal products and cultivars.