Increased enzyme production under liquid culture conditions in the industrial fungus <i>Aspergillus oryzae</i> by disruption of the genes encoding cell wall α-1,3-glucan synthase

Under liquid culture conditions, the hyphae of filamentous fungi aggregate to form pellets, which reduces cell density and fermentation productivity. Previously, we found that loss of α-1,3-glucan in the cell wall of the fungus <i>Aspergillus nidulans</i> increased hyphal dispersion. Therefore, here we constructed a mutant of the industrial fungus <i>A. oryzae</i> in which the three genes encoding α-1,3-glucan synthase were disrupted (tripleΔ). Although the hyphae of the tripleΔ mutant were not fully dispersed, the mutant strain did form smaller pellets than the wild-type strain. We next examined enzyme productivity under liquid culture conditions by transforming the cutinase-encoding gene <i>cutL1</i> into <i>A. oryzae</i> wild-type and the tripleΔ mutant (i.e. wild-type-cutL1, tripleΔ-cutL1). <i>A. oryzae</i> tripleΔ-cutL1 formed smaller hyphal pellets and showed both greater biomass and increased CutL1 productivity compared with wild-type-cutL1, which might be attributable to a decrease in the number of tripleΔ-cutL1 cells under anaerobic conditions. Summary of the growth characteristic and enzyme productivity in <i>A. oryzae ags</i> tripleΔ strain.