Production of sulfated oligosaccharides from the seaweed Ulva sp. using a new ulvan-degrading enzymatic bacterial crude extract

•The polysaccharide ulvan was successfully extracted from the green alga Ulva ohnoi.•A new ulvan degrading bacterium, belonging to the genus Alteromonas, was isolated.•The enzymes responsible for the degradation of ulvan have been isolated.•Small sulfated oligosaccharides were purified and separated by HPTLC.•1H NMR of oligosaccharides shows the presence of a potentially new ulvan-lyase.

Green macroalgae of the genus Ulva have complex and hardly degradable polysaccharidic extracellular matrix. One of its main components, the ulvan, is a 3-sulfated rhamnoglucuronan that has a wide range of properties and is a source of rare sugars. The production of mono- and oligo-saccharides from this polysaccharide could motivate its use to an industrial scale. Enzymatic tools to realize this process are still scarce. Here we describe the activity of an enzyme crude extract proceeding from a new Alteromonas species isolated from the gut of Gammarus insensibilis, an amphipod from southern Spanish salt marshes. HPTLC separation and NMR spectrometry allowed describing the formation of low molecular weight oligosaccharides formed principally of unsaturated 3-sulfated rhamnose and uronic acids. The control of hydrolysis kinetics allowed preparing different molecular weight fractions down to a 5 kDa oligosaccharides mix. These results highlight the presence of a potentially new β-lyase produced by these hitherto undescribed bacteria. This work identifies a new source of enzymes with potential application for the production of high added value compounds from Ulva sp.