For aerobic fermentation process, oxygen supply is of great importance because it is often the critical factor to obtain the appropriate KLa value that correlates with productivity in fermentation media [18] and [19]. In this study, KLa had apparent effect on the cell growth and DHA production of Schizochytrium sp. in fed-batch fermentation process. Our previous study [14] also had the similar results as this study. These results might be explained by the fact that oxygen transfer into microbial cells intensively affects product formation by impacting metabolic pathways and altering metabolic fluxes [20].