Patent ID: 8507227

Claim:
A method for producing a sialylated oligosaccharide, comprising: a) culturing an Escherichia coli microorganism, comprising heterologous genes encoding a CMP-Neu5Ac synthetase, a sialic acid synthase, a GlcNAc-6-phosphate 2 epimerase and a sialyltransferase, wherein endogenous genes coding for sialic acid aldolase (NanA) and for ManNac kinase (NanK) have been deleted or inactivated, and wherein said microorganism produces internally, activated sialic acid as donor substrate for said sialyltransferase; and b) culturing said microorganism in a culture medium comprising an exogenous precursor selected from the group consisting of lactose, galactose, β-galactoside, and α-galactoside, wherein active uptake into the microorganism of said exogenous precursor occurs and wherein said exogenous precursor is the acceptor substrate for said sialytransferase for producing the sialylated oligosaccharide.