The present invention describes methods and processes for the production of proteins, particularly glycoproteins, by animal
cell or
mammalian cell culture, illustratively, but not limited to, fed-batch
cell cultures. The methods comprise feeding the cells with D-
galactose, preferably with feed medium containing D-
galactose, preferably daily, to sustain a sialylation effective level of D-
galactose in the culture for its duration, thus increasing sialylation of the produced proteins. The methods can also comprise at least
two temperature shifts performed during the culturing period, in which the temperature is lower at the end of the culturing period than at the time of
initial cell culture. The
cell culture processes of the invention involving two or more temperature shifts sustain a
high cell viability, and can allow for an extended
protein production phase. The methods can also comprise the delayed addition of polyanionic compound at a time after innoculation. Supplementation of the cultures with D-galactose, preferably in a feed medium, to sustain galactose at sialylation effective levels in the cultures until the end of a culture run reverses a decline in sialylation that accompanies culture scale up, and is advantageous for large scale culturing processes.