Biological pretreatment of coffee pulp

Abstract The presence of several antiphysiological factors limit the use of coffee pulp in monogastric and ruminant feeding. Among these the characteristics of its lignocellulosic fraction is important. Twenty-six white rot fungi were grown under solid substrate conditions, using previously ensiled and pressed coffee pulp without adding additional sources of nitrogen; the objective was to quantify the changes of the lignocellulosic polymer matrix and the enzymatic digestibilities. All grew and wholly covered the surface of the substrate. Six of the fungi produced fruiting bodies, which were easy to see since basidiomycetes produce large fuiting bodies. The weight loss interval ranged between 6·7 and 28·0% dry matter before fructification and from 17·0 to 48·7% after fructification. Trametes versicolor was a very fast grower and showed the highest rates of holocellulose and lignin degradation. Hemicellulose was selectively preferred over cellulose by most fungi and at least two degraded more than 80% of the original hemicellulose. Six white rots produced a solid residue with less lignin content than the one found in the original substrate. Two of them, Sporotrichum pulverulentum and Stropharia rugosoannulata , also increased the water-soluble solids and produced a solid residue with the same enzymatic digestibility as the one found for the original coffee pulp.