A. Sachslehner et al., INDUCTION OF MANNANASE, XYLANASE, AND ENDOGLUCANASE ACTIVITIES IN SCLEROTIUM-ROLFSII, Applied and environmental microbiology, 64(2), 1998, pp. 594-600
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.