Abstract: This work sought to develop a fermentative process for the microbial production of superoxide dismutase (SOD), to overcome extraction from animal tissues. Twenty-eight wild-type yeast strains were screened for SOD productivity. Kluyveromyces marxi- anus L3 showed the highest SOD activity (62 U mg¡1) and was used for process development. Oxidative stress conditions and parameters aVecting oxygen transfer rate were exploited to improve production. The eVects of dilution rate (0.067 vs 0.2 h¡1), aeration pressure (0.3 vs 1.2 bar) and H2O2 (0 vs 50 mM) were studied during chemostat experiments. Low dilution rate, high pressure and H2O2 resulted in an increase in CuZn–SOD up to 475 U mg¡1. When a regulation of oxygen saturation was applied during batch cultures, CuZn–SOD was progressively higher at 60, 80 and 90% dissolved oxygen tension (DOT) (250, 330 and 630 U mg¡1, respectively). Furthermore, the highest growth rate and biomass yield were achieved at 90% DOT, this being therefore the best DOT condition for high overall productivity. Growth and productivity on diVerent carbon sources were compared. SpeciWc activ- ity was higher on glycerol than on lactose or glucose (496, 454 and 341 U mg¡1, respectively). The highest biomass yield was achieved on lactose. It may be there- fore the best substrate for SOD production.
