Endo-beta-1,4-D-mannanase is efficiently produced by Sclerotium (Athelia) rolfsii under derepressed conditions

A number of wild-type isolates of Sclerotium (Athelia) rolfsii and S. coffe icola were studied for their ability to produce endo-beta-1,4-mannanase, en do-beta-1,4-xylanase, and endo-beta-1,4-glucanase activity when grown on ce llulose- or glucose-based media. Whereas the presence of the inducer cellul ose was strictly necessary for increased xylanase and endoglucanase product ion by both S. rolfsii (208 and 599 U ml(-1), respectively) and S. coffeico la (102 and 330 U ml(-1), respectively), elevated activities of mannanase ( up to 96.6 U ml(-1)) were formed even when employing glucose as the only ca rbohydrate substrate. Significant production of mannanases as well as of au xiliary mannan-degrading enzymes (beta-mannosidase, beta-glucosidase, alpha -galactosidase, acetyl esterase) was only observed, however, under derepres sed conditions, i.e. after glucose had been consumed from the medium. By ap plying a fed-batch strategy, in which a glucose solution was continuously f ed to a cultivation of S. rolfsii CBS 191.62 so that the glucose concentrat ion in the medium never exceeded a certain low, critical value, production of mannanase could be almost doubled as compared to a batch cultivation on glucose (462 versus 240 U ml(-1)). Mannanase preparations produced by sever al S. rolfsii and S. coffeicola strains under inductive and noninductive co nditions (i.e. using cellulose or glucose as the substrates, respectively) were further analyzed with respect to the patterns of isoformic mannanases formed under these different growth conditions. Multiple mannanases were se creted by all isolates investigated. Certain mannanase isoenzymes were only formed by S. rolfsii in the presence of the inducer cellulose, indicating a complex and separated regulation of the synthesis of mannanase isoenzymes in this strain. (C) 1999 Elsevier Science B.V. All rights reserved.