Sialyltransferases and their use in producing sialylated oligosaccharides

A method for producing one or more sialylated oligosaccharides by whole cell fermentation, the method comprising:

• a) providing at least one genetically engineered cell which comprises a heterologous sialyltransferase, wherein said heterologous sialyltransferase possesses an α-2,3-sialyltransferase activity and/or an α-2,6-sialyltransferase activity for transferring a sialic acid residue from a nucleotide-activated form as donor substrate to an acceptor molecule,
• wherein the acceptor molecule is lacto-N-tetraose, and
• wherein the heterologous sialyltransferase is selected from
• i) polypeptides comprising an amino acid sequence of any one of SEQ ID NOs:
• 34, 36, 62 and 63;
• and
• ii) fragments of polypeptides comprising an amino acid sequence of any one of SEQ ID NOs:
• 34, 36, 62 and 63;
• and
• b) cultivating the at least one cell in a fermentation broth and under conditions permissive for the production of said sialylated oligosaccharide during cultivation in the fermentation broth;
• and
• c) recovering said sialylated oligosaccharide from the fermentation broth.