Effect of cultural conditions on the synthesis of superoxide dismutase by Humicola lutea 110

Superoxide dismutase (SOD) was produced by the fungal strain Humicola lutea 110. Some of the factors influencing both enzyme and biomass production were studied in shake-flask cultures: glucose and nitrogen concentration, inoculum quantily, and temperature. The best results were obtained for a fermentation performed with 4% glucose, 0.152% nitrogen source, and 8% inoculum at 30°C. The time course of SOD biosynthesis showed two maxima (84.1 and 120.8 U/mg protein SOD activity respectively), which correspond to the maxima of the biomass. The dramatic increase in SOD activity during the late stationary stage indicated that the processes of O2− generation were intensified in the cells. Mn-SOD was responsible for the modulation of total SOD activity at both maxima.