INDUCTION OF MANNANASE, XYLANASE, AND ENDOGLUCANASE ACTIVITIES IN SCLEROTIUM-ROLFSII

Induction of mannanase, xylanase, and cellulase (endoglucanase) synthe sis in the plant-pathogenic basid iomycete Sclerotium rolfsii was stud ied by incubating noninduced, resting mycelia with a number of mono-, oligo-, and polysaccharides. The simultaneous formation of these three endoglycanases could be provoked by several polysaccharides structura lly resembling the carbohydrate constituents of lignocellulose (e.g., mannan and cellulose), by various disaccharide catabolites of these li gnocellulose constituents (e.g., cellobiose, mannobiose, and xylobiose ), or by structurally related disaccharides (e.g., lactose, sophorose, and galactosyl-beta- 1,4-mannose), as well as by L-sorbose. Synthesis of mannanase, xylanase, and endoglucanase always occurred concomitant ly and could not be separated by selecting an appropriate inducer. Var ious structurally different inducing carbohydrates promoted the excret ion of the same multiple isoforms of endoglycanases, as judged from th e similar banding patterns obtained in zymogram analyses of enzyme pre parations obtained in response to these different inducers and resolve d by analytical isoelectric focusing. Whereas enhanced xylanase and en doglucanase formation is strictly dependent on the presence of suitabl e inducers, increased levels of mannanase are excreted by S. rolfsii e ven under noninducing, derepressed conditions, as shown in growth expe riments with glucose as the substrate. Significant mannanase formation commenced only when glucose was exhausted from the medium, Under thes e conditions, only very low, presumably constitutive levels of xylanas e and endoglucanase were formed. Although the induction of the three e ndoglycanases is very closely related in S. rolfsii, it was concluded that there is no common, coordinated regulatory mechanism that control s the synthesis of mannanase, xylanase, and endoglucanase.