Cell wall architecture as well as chemical composition determines fermentation of wheat cell walls by a faecal inoculum

Grain cell walls are a common component of the human diet, and an important source of dietary fibre. They primarily consist of a cellulose matrix incorporating arabinoxylan (AX) and mixed linkage (1, 3)(1, 4)-beta-glucan (MLG). In this study, cell walls isolated from wheat flour (WCW) were compared with a physical mixture (Mix) of the major WCW polysaccharides (AX, MLG and cellulose) in the proportions found in WCW. WCW, Mix and the individual polysaccharides were subjected to in vitro fermentation for 48 h with a porcine fecal inoculum. Each constituent in Mix was fermented to a similar extent as single-component substrates, indicated by the total amount of gas and short chain fatty acid (SCFA) produced. However, WCW showed a slower production of gas and SCFA and slower degradation of its non-cellulosic polysaccharides. This suggests that the architecture of WCW plays a critical role in determining the rate of fecal microbial fermentation.