GO:0003835:   beta-galactoside alpha-2,6-sialyltransferase activity
Catalysis of the reaction: CMP-N-acetylneuraminate + beta-D-galactosyl-(1->4)-acetyl-beta-D-glucosamine = CMP + alpha-N-acetylneuraminyl-(2->6)-beta-D-galactosyl-(1->4)-N-acetyl-beta-D-glucosamine.