Differential antioxidant activity of glucuronooligosaccharides (UXOS) and arabinoxylooligosaccharides (AXOS) produced by two novel xylanases.

XOS are particular interesting bioactive molecules. Bacillus safensis CBLMA18, a xylanolytic bacterium has been isolated and two of their xylanases have been identified and fully characterized. Xyn11A is an extracellular 22.5-kDa GH11 xylanase while a second xylanase, Xyn10B, corresponds to an intracellular 48-kDa GH10 enzyme. Both unimodular xylanases showed activity only on xylanolytic substrates with important differences in their catalytic pattern. Xyn11A displays higher activity on glucuronoxylans, with an optimum at pH 8 and 50 °C, and a V_max of 5281 U/mg on beechwood xylan, meanwhile Xyn10B prefers arabinoxylans, with an optimum of pH 7 and 60 °C, and a V_max of 50.29 U/mg on rye arabinoxylan. The antioxidant activity of xylanase-generated XOS obtained from glucuronoxylans (UXOS) and arabinoxylans (AXOS) was tested with the ABTS (2, 2'-Azino-bis (3-ethylbenzothiazoline-6-sulfonic acid)) method. UXOS showed higher antioxidant activity than AXOS (>80% of antioxidant capacity). Thin layer chromatography and MALDI-TOF MS analysis showed that UXOS comprise neutral and acidic XOS with methylglucuronic acid (MeGlcA) ramifications, while AXOS contain only neutral molecules with arabinose decorations. The MeGlcA ramifications seem to have an important role in the antioxidant capacity of oligosaccharides. Besides, the increase of UXOS size correlates with an increase in their activity.