Method for producing glycoprotein compositions

A method for recombinantly producing a glycoprotein composition comprising at least one glycoprotein in a recombinant host cell which expresses the glycoprotein, comprising the steps of

• (a) providing a bioreactor comprising a pH measuring device positioned in the bioreactor and configured to be in physical contact with a cultivation medium,
• (b) closing and sterilizing the bioreactor,
• (c) filling the cultivation medium into the bioreactor,
• (d) calibrating the pH measuring device,
• (e) inoculating the bioreactor with the recombinant host cell,
• (f) cultivating the recombinant host cell under conditions suitable for producing the glycoprotein composition, and
• (g) thereby producing the glycoprotein composition,
• characterized in that the calibrating of step (d) comprises the steps of
• (i) introducing a gas mixture comprising carbon dioxide gas into the bioreactor,
• (ii) determining the carbon dioxide concentration in the headspace and/or the exhaust,
• (iii) calculating the pH value of the cultivation medium based on a media specific correlation, and
• (iv) adjusting the pH measuring device to the pH value calculated in step (iii).

A method of reducing the variability of the relative content of at least one glycosylated variant between batches of a recombinant glycoprotein, the method comprising:

• (a) providing a bioreactor comprising a pH measuring device positioned in the bioreactor and configured to be in physical contact with a cultivation medium,
• (b) closing and sterilizing the bioreactor,
• (c) filling the cultivation medium into the bioreactor,
• (d) calibrating the pH measuring device,
• (e) inoculating the bioreactor with a recombinant host cell which expresses the glycoprotein, and
• (f) cultivating the recombinant host cell under conditions suitable for producing the glycoprotein, and
• (g) thereby producing the glycoprotein,
• wherein the calibrating of step (d) comprises the steps of
• (i) introducing a gas mixture comprising carbon dioxide gas into the bioreactor,
• (ii) determining the carbon dioxide concentration in the headspace and/or the exhaust gas of the bioreactor,
• (iii) calculating the pH value of the cultivation medium based on a media specific correlation, and
• (iv) adjusting said pH measuring device to the pH value calculated in step (iii), and
• wherein steps (a) to (g) result in a first batch of said recombinant glycoprotein with a defined relative content of the glycosylated variant;
• (h) repeating the steps (a) to (g) resulting in at least one subsequent batch of said glycoprotein, wherein the relative content of the at least one glycosylated variant of said first and at least one subsequent batch has reduced batch-to-batch variability.