Polysaccharide synthesis by capsular microorganisms in coculture with cellulolytic fungi on straw and stabilization of soil aggregates

Summary Studies using cocultures of a cellulolytic fungus with a capsular organism show that microbial polysaccharides can be synthesized during the degradation of wheat straw. Polysaccharide accounted for up to 1.6% (w/w) of the initial straw weight but the sugar composition and viscosity indicated that a large fraction was low molecular weight material of plant origin. Nevertheless several cocultures produced sufficient microbial polysaccharide effectively to stabilize aggregates of Hamble silt loam. This correlated significantly with increased viscosity and also stabilization of Mount St. Helens volcanic ash. Four cocultures, Sordaria alcina with two strains of Enterobacter cloacae and a Pseudomonas sp. and Trichoderma harzianum with E. cloacae, were significantly more effective than a natural inoculum from straw. Inoculation of straw to produce a compost which can increase the stability of poorly structured soils is suggested.