Structure of oligosaccharide F21 derived from exopolysaccharide WL-26 produced by Sphingomonas sp. ATCC 31555

► F21 was isolated and purified from exopolysaccharide WL-26. ► Its structure was determined by sugar analysis, 1H, 13C and 2D NMR spectroscopy. ► It was a homogeneous oligosaccharide and the molecular weight was 1.4 × 103 Da by HPLC.