The Effect of Bioreactor pH and Temperature on Protein Glycosylation in Perfusion Cultures of Mammalian Cells

Abstract

Bioreactor pH, ranging from 6.7 to 7.2, was evaluated in several 2L perfusion bioreactors. Prolonged exposure to pH between 6.7 and 6.9 has no impact on alpha (1–3)-galactose levels for a rBHK cell line. However, prolonged exposure to high pH (pH > 7.0) significantly increased the alpha-gal level. Interestingly, the recombinant protein alpha-gal level correlated qualitatively with the cell surface alpha-gal levels measured by FACS and the gene expression of alpha-1,3- galactosyltransferase measured by RT-PCR. This indicates that the effects of bioreactor culture pH on alpha-gal levels are not specific to the recombinant protein. Furthermore lowering the cultivation temperatures from 35.5^°C (std. conditions) to 34.0^°C significantly reduced the terminal sialic acid content by about 10%, while the overall glycosylation profile was unchanged.