Effects of xylan and starch on secretome of the basidiomycete Phanerochaete chrysosporium grown on cellulose.

Lignocellulosic biomass contains cellulose and xylan as major structural components, and starch as a storage polysaccharide. In the present study, we have used comparative secretomic analysis to examine the effects of xylan and starch on the expression level of proteins secreted by the basidiomycete Phanerochaete chrysosporium grown on cellulose,. Forty-seven spots of extracellular proteins expressed by P. chrysosporium separated by two-dimensional electrophoresis were identified by liquid chromatography-tandem mass spectrometry analysis. Addition of starch to the cellulolytic culture did not affect fungal growth significantly, but did decrease the production of total extracellular enzymes, including cellulases and xylanases. In contrast, addition of xylan increased mycelial volume and the production of extracellular proteins. Xylan increased synthesis of several glycoside hydrolase (GH) family 10 putative endoxylanases and a putative glucuronoyl esterase belonging to carbohydrate esterase family 15, for which plant cell wall xylan may be a substrate. Moreover, cellobiose dehydrogenase and GH family 61 proteins, which are known to promote cellulose degradation, were also increased in the presence of xylan. These enzymes may contribute to degradation by the fungus of not only cellulose but also complex carbohydrate components of the plant cell wall.