Biosynthesis of superoxide dismutase and catalase in chemostat culture of Saccharomyces cerevisiae

Abstract

The effects of oxygen (100%), paraquat (0.5 mM), and copper (0.1 mM) on the growth and the biosynthesis of the antioxidant enzymes, superoxide dismutase (SOD) and catalase, were studied in Saccharomyces cerevisiae grown in glucose-limited chemostat cultures. The effect of dilution rates (D, h−1) on cell mass, glucose consumption, ethanol production, oxygen uptake, and specific activities of SOD and catalase were also investigated at each steady state. SOD was optimally produced at D-values between 0.22 and 0.26 h−1 in the presence of oxygen or paraquat, and at D-values greater than 0.17 h−1 when copper was used. On the other hand, catalase activity decreased with increasing D-values. However, the presence of copper or 100% oxygen repressed catalase activity at low D-values (D 0.22 h−1). We also studied the effect of oxygen concentration on the biosynthesis of SOD and catalase at D=0.1 h−1. The data clearly show that synthesis of SOD and catalase, though correlated with changes in oxygen tension, are independent of one another.