A method for the production of a polypeptide comprising the following steps - cultivating a cell comprising a nucleic acid encoding the polypeptide in a fed-batch or continuous cultivation with a cultivation vessel comprising a device for adding at least two feed solutions each with a non-physiological pH value to the cell cultivation vessel comprising separate inlets for the feed solutions, a chamber for mixing the feed solutions, and a single outlet for adding the mixed feed solutions to the cell cultivation vessel, whereby the ratio of the volume of the chamber for mixing the feed solutions to the volume of cultivation medium in the cultivation vessel is of from 0.8 ml/l to 1.2 ml/l or an apparatus comprising a) a cell cultivation vessel, b) a gas supply, c) at least two liquid storage units for feed solutions each with a non-physiological pH value, d) at least a sensor for determining the pH value in the cell cultivation vessel, and e) a device for adding at least two feed solutions each with a non-physiological pH value to the cell cultivation vessel comprising separate inlets for the feed solutions, a chamber for mixing the feed solutions, and a single outlet for adding the mixed feed solutions to the cell cultivation vessel, whereby the ratio of the volume of the chamber for mixing the feed solutions to the volume of cultivation medium in the cultivation vessel is of from 0.8 ml/l to 1.2 ml/l, wherein at least two feed solutions each with a non-physiological pH value are added to the cultivation medium, and - recovering the polypeptide from the cultivation medium or the cells. - cultivating a cell comprising a nucleic acid encoding the polypeptide in a fed-batch or continuous cultivation with a cultivation vessel comprising a device for adding at least two feed solutions each with a non-physiological pH value to the cell cultivation vessel comprising separate inlets for the feed solutions, a chamber for mixing the feed solutions, and a single outlet for adding the mixed feed solutions to the cell cultivation vessel, whereby the ratio of the volume of the chamber for mixing the feed solutions to the volume of cultivation medium in the cultivation vessel is of from 0.8 ml/l to 1.2 ml/l or an apparatus comprising a) a cell cultivation vessel, b) a gas supply, c) at least two liquid storage units for feed solutions each with a non-physiological pH value, d) at least a sensor for determining the pH value in the cell cultivation vessel, and e) a device for adding at least two feed solutions each with a non-physiological pH value to the cell cultivation vessel comprising separate inlets for the feed solutions, a chamber for mixing the feed solutions, and a single outlet for adding the mixed feed solutions to the cell cultivation vessel, whereby the ratio of the volume of the chamber for mixing the feed solutions to the volume of cultivation medium in the cultivation vessel is of from 0.8 ml/l to 1.2 ml/l, wherein at least two feed solutions each with a non-physiological pH value are added to the cultivation medium, and a) a cell cultivation vessel, b) a gas supply, c) at least two liquid storage units for feed solutions each with a non-physiological pH value, d) at least a sensor for determining the pH value in the cell cultivation vessel, and e) a device for adding at least two feed solutions each with a non-physiological pH value to the cell cultivation vessel comprising separate inlets for the feed solutions, a chamber for mixing the feed solutions, and a single outlet for adding the mixed feed solutions to the cell cultivation vessel, whereby the ratio of the volume of the chamber for mixing the feed solutions to the volume of cultivation medium in the cultivation vessel is of from 0.8 ml/l to 1.2 ml/l, - recovering the polypeptide from the cultivation medium or the cells.