Cellobiose dehydrogenase influences the production of S. microspora β-glucosidase

BglG, a Stachybotrys microspora β-glucosidase produced in the presence of glucose and cellobiose, was used individually as sole carbon source. The time course synthesis of BglG showed two aspects: (1) an exponential curve, observed in glucose Mandels medium, and (2) a cloche curve, observed in cellobiose containing cultures. A decrease was observed in bglG production at the 6th, 8th and 10th days during mycelium growth in cellobiose Mandels medium, which allowed for the assumption that the anabolism of a bglG inhibitor factor was produced with cellobiose but not with glucose. Cellobiose dehydrogenases (CDH) activity was, on another hand detected in cellobiose grown cultures but not in glucose containing ones. The aliquots, withdrawn at the time course of bglG production in the presence of cellobiose, gave rise to an inhibitory effect on bglG activity. This result was obtained with and without the heat treatment (5 min at 100°C) of the aliquots, which supported the non-proteinaceous nature of the inhibitor factor. Furthermore, sugar chromatographic analyses revealed the appearance of a secondary metabolite in the cellobiose Mandels medium and indicated that the factor behind the bglG activity cloche curve was a δ-gluconolactone. Seeing that the latter follows a strong inhibitory effect on bglG activity, it is speculated that the decrease in bglG activity during the time course of bglG synthesis in cellobiose Mandels medium is assigned to the release of δ-gluconolactone. This paper presents and validates an explanatory model for this hypothesis.