Production of glycoproteins with low N-glycolylneuraminic acid (NEU5GC) content

A method for producing a glycoprotein, the method comprising the steps of (a) cultivating eukaryotic cells in a medium comprising as (an) additive(s) dimethyl sulfoxide (DMSO), N-acetylmannosamine (NAcMan), N-acetylglucosamine (NAcGlc), or any combination of two or more of these additives, including the combination of NAcMan and NAcGlc and (b) recovering from that medium, or from said cells, the glycoprotein, wherein the glycoprotein exhibits (i) a degree of sialylation that is identical to or higher than the degree of sialylation of the same glycoprotein when produced in the same medium but without the additive(s);

• and (ii) a content of N-glycolylneuraminic acid (Neu5Gc) that is lower than the content of Neu5Gc of the same glycoprotein when produced in the same medium but without the additive(s), wherein the medium additionally comprises iron in a concentration range selected from the group consisting of 0.05 to 0.1, 0.070 to 0.09, and 0.075 to 0.08 mM.