A transformed bryophyte cell that comprises six heterologous nucleotide sequences each operably linked to an exogenous promoter that drives expression in the bryophyte cell wherein said six nucleotide sequences encode six functional proteins that are expressed in the bryophyte cell, wherein said six functional proteins are a mammalian UDP-N-acetylglucosamine-2-epimerase/N-acetylmannosamine-6-kinase, a mammalian N-acetylneuraminic acid phosphate synthase (sialic acid synthase), a mammalian CMP-N-acetylneuraminic acid synthase, a mammalian CMP-sialic acid transporter, a galactosyltransferase, and a mammalian sialyltransferase.