Effect of osmotic stress on glucose oxidase production and secretion by Aspergillus niger

A mycelium of Aspergillus niger was cultured under various osmotic stresses. When fungus was cultured under osmotic stress, total catalase activity increased with increasing concentration of NaCl, up 0.4 M, but glucose oxidase under this condition significantly decreased. Mycelial growth was repressed with increased media osmolarity. To release periplasmic glucose oxidase 72-h old mycelium was suspended on a concentrated solution of NaCl (0.4-2.8 M/l). The highest yield of GOD activity was obtained at a NaCl concentration of 1.2 M at pH 6.0, which improved the activity of this enzyme by about 2.1-fold in comparison with the control medium without this depressor.