Mechanism of Overproduction of Secreted Enzymes in the Mycelial Fungus Penicillium canescens

The fungus Penicillium canescens strain F178 (VKPM) and its niaD ^– mutant exhibited an increased capability of synthesizing extracellular enzymes -galactosidase (50–60 U/ml) and xylanase (100 U/ml). The synthesis was induced by arabinose and its catabolite, arabitol. A deficiency in arabitol dehydrogenase, leading to arabitol accumulation in the cell, was detected in the chain of reactions of arabinose catabolism. The increased synthesis of -galactosidase and xylanase in P. canescens is accounted for by (1) cellular accumulation of the inducer (arabitol) at low concentrations of arabinose in the medium and (2) prevalence of induction over repression.