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Fermentation of a bacterial cellulose/xylan composite by mixed ruminal microflora: implications for the role of
P J Weimer1, J M Hackney, H J Jung
1U.S. Dairy Forage Research Center, Agricultural Research Service, U. S. Department of Agriculture, Madison, Wisconsin 53706, USA. pjweimer@facstaff.wisc.edu
Abstract:
Growth of the cellulose-synthesizing bacterium Acetobacter xylinum ATCC 53524 in media supplemented with 5% (w/v) glucose and 0.2% (w/v) of a water-soluble, nearly linear xylan from tobacco stalks resulted in the synthesis of a highly crystalline composite having a xylose/glucose ratio ranging from 0.06 to 0.24. The digestion of one composite (88% cellulose/12% xylan) by mixed ruminal microflora displayed kinetics of gas production similar to those of an unassociated mixture of the two components added in a xylan/cellulose ratio similar to that of the composite. The data suggest that intimate association of xylan and cellulose, as is typically found in secondary plant cell walls, does not inhibit the rate of digestion of the component polysaccharides.