Strictly anaerobic bacteria in the evolutionary way formed some mechanisms of oxygen tolerance. These changes enable strictly anaerobic bacteria existing in natural environment in which avoiding oxygen is not possible. Clostridium bifermentans is described as a strictly anaerobe species; however, in the literature, there is some information about its oxygen tolerance. Thus, in this work, the level of C. bifermentans aero-tolerance, its mechanisms, and the ability to metabolite production in presence of oxygen in cultivation medium were investigated. It was found out that C. bifermentans is able to survive in the presence of oxygen. Moreover, they are able to utilize oxygen and product metabolites when the level of oxygen is below 10%. In bacteria cells superoxide dismutase was detected.