Oxygen transfer rates in a mammalian cell culture bioreactor equipped with a cell-lift impeller

Measurements of k(L)a were carried out in 1. 5- and 5-L New Brunswick Scientific CelliGen(R) bioreactors. The measured k(L)a in water were identical for both vessel sizes operated in similar condition. The mass transfer rate increased with temperature, mixing speed, and aeration rate, with this last parameter being the most significant. Surface aeration alone gave k(L)a values of 0. 4 to 1. 6 h(-1). A 25% decrease in k(L)a was observed above an aeration rate of 1. 6 vvm. This was caused by the particular foam breaker of the CelliGen bioreactor. Measurements of k(L)a using a mammalian cell culture medium supplemented with 5% fetal calf serum (FCS) have confirmed the negative effect of the foam breaker on k(L)a The measured value in this medium was 1. 2 h(-1) for all aeration rates, more than 60% of which was attributed to surface aeration.