Cultivation of Arabidopsis cell cultures in a stirred bioreactor at variable oxygen levels: influence on tocopherol production

In plants, an increased production of toxic oxygen species is commonly observed under low oxygen stress, but cellular responses still have to be fully investigated. Plant cell cultures can be a valuable tool to study plant metabolic responses to various environmental stresses including low oxygen condition. Arabidopsis suspension cultures growing in shake flasks were subjected to hypoxia by stopping shaking for different intervals, showing an increase of the antioxidant metabolite a-tocopherol. In order to obtain a more controlled condition, cultivation of Arabidopsis suspension cultures was established in a 5-L stirred bioreactor. A constant aeration of 20 % dissolved oxygen was found to be the most suitable for cell growth. A 4-hour anoxic shock was induced by suspending the aeration and flushing into the vessel with nitrogen. During the anoxic stress, tocopherol levels resulted increased at the end of the treatment, indicating that the complete oxygen deprivation indeed induced a defence response involving antioxidant metabolism. The presence of an oxidative stress as a consequence of anoxic condition was also confirmed by the increased levels of H2O2. Overall, these results indicate that Arabidopsis suspension cultures grown in a stirred bioreactor can be a useful in vitro system for investigating low oxygen stress.