The relationship of oxygen uptake rate and k(L)a with rheological properties in high cell density cultivation of docosahexaenoic acid by Schizochytrium sp. S31.

Three independent cultures by fed batch strategy under different oxygen supply levels were investigated with Schizochytrium sp. S31 on glycerol in 50 L bioreactor. Three cultures all achieved high cell density cultivation (HCDC) with more than 100 g/L biomass density. However, the culture with middle oxygen supply level achieved the highest DHA concentration at 21.26 g/L. Dissolved oxygen (DO) limitation was commonly encountered in the present cultures, which was due to the dramatic decrease of kLa in high oxygen supply culture resulted from significantly increasing apparent viscosity of the broth. The rheological properties of the three cultures all exhibited shear-thinning behavior. The oxygen uptake rate (OUR) predominately influenced by kLa was suggested to replace DO as on-line control parameter for scale-up production of DHA.