Regulation of the synthesis of xylan- and mannan-degrading enzymes in Sclerotium rolfsi.

Induction of mannanase, xylanase and cellulase (endoglucanase) synthesis in the plant pathogenic basidiomycete Sclerotium rolfsii was studied. The simultaneous formation of these three endoglycanases could be provoked by several polysaccharides structurally resembling the carbohydrate constituents of lignocellulose or by various disaccharide catabolites of these lignocellulose constituents. Synthesis of mannanase, xylanase and endoglucanase always occurred concomitantly and could not be separated by selecting an appropriate inducer. Whereas enhanced xylanase and endoglucanase formation is strictly dependent on the presence of suitable inducers, increased levels of mannanase are excreted by S. rolfsii even under noninducing, derepressed conditions as was shown in growth experiments using glucose as the substrate. Mannanase activity formed under these derepressed conditions could be mainly attributed to one major, acidic mannanase isoenzyme of a pI value of 2.75.