Fermentation of the endosperm cell walls of monocotyledon and dicotyledon plant species by faecal microbes from pigs: The relationship between cell wall characteristics and fermentability

Cell walls from the endosperm of four monocotyledons (maize, wheat, rye, and rice) and four dicotyledons (soya bean, lupin, faba bean, and pea) seeds were studied to relate cell wall composition and structure with fermentation characteristics. Cell wall material was isolated from the endosperm of the mono- and dicotyledons. The fermentation characteristics of isolated cell walls from mono- and dicotyledons were analysed in two separate in vitro gas production experiments. At 0, 12, 24, 36, 48, and 144 h of fermentation, fermentation was stopped in selected bottles to analyse VFA production (144 h only) and sugar degradation patterns. The relationship between cell wall characteristics (composition, particle size) and fermentation characteristics (half-time of gas production and maximal rate of substrate degradation) was analysed using linear regression. For the monocotyledon cell walls, the rate of substrate degradation was decreased by increasing particle size of the cell walls, a clear effect of cell wall composition on fermentation characteristics could not be determined, though this might have been obscured by the differences in particle size. During fermentation of the monocotyledon cell wall, arabinoxylans (arabinose and xylose) and cellulose (glucose) appeared to be degraded simultaneously. For the dicotyledon cell walls, an increase in total sugar content decreased the half-time of gas production, though total sugar content was probably confounded with the crude protein content. During fermentation of the dicotyledon cell wall, pectins or pectin-related sugars (galactose, arabinose, uronic acids) appeared to be degraded faster than cellulose, whereas for the monocotyledon cell walls, arabinoxylans and cellulose were degraded simultaneously. The differences in cell wall fermentation and sugar degradation pattern between monocotyledon and dicotyledon cell walls are discussed in relation to differences in cell wall architecture.