NeuNAc, ManNAc and GlcNAc formation was measured using LC-MS (IT-TOF-MS) (Shimadzu, Kyoto, Japan) with a Rezex™ RHM-Monosaccharide H + -column (8%, 300 × 7.8 mm) (Phenomenex, Torrance, USA). The mobile phase consisted of water with 0.1% (v/v) trifluoroacetic acid, the flow was 0.6 mL/min, the column temperature was 80°C, and the injected volume was 10 μL. MS detection was performed in ESI+ mode, covering a scan range of 60-600 amu. The retention times were determined using pure standard substances. The identity of NeuNAc was confirmed by both, chromatographic retention time and mass spectral signal, which are very well matched by authentic standards of NeuNAc. The better the mass accuracy obtained from exact mass determination by HR-MS, the lower is the number of possible isobaric candidates (e.g. [35] ). In this case the mass accuracy is better than 2 ppm, leading to the number of candidates reduced to less than 10, with an even further reduction in the number of potential candidates because the isotopic pattern is also taken into account (what the software of the used IT-TOF-MS instrument does automatically).