Acidic xylooligosaccharides (XOS), also called aldouronics, are hetero-oligomers of xylose randomly branched with 4-O-methyl-D-glucuronic acid residues linked by α(1 → 2) bonds, which display bioactive properties. We have developed a simple and integrated method for the production of acidic XOS by enzymatic hydrolysis of a glucurono-xylan from beechwood. The acidic fraction contained a major product, characterized by matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF) mass spectrometry and mono- and two-dimensional nuclear magnetic resonance spectroscopy (NMR) as 2′-O-α-(4-O-methyl-α-D-glucuronosyl)-xylobiose (X2_MeGlcA). Starting from 2 g of beechwood xylan, 1.5 g of total XOS were obtained, from which 225 mg (11% yield) corresponded to the aldouronic X2_MeGlcA. The acidic XOS exhibited higher antioxidant activity (measured by the ABTS·+ discoloration assay) than xylan, whilst neutral XOS displayed no antioxidant activity. This work demonstrates that it is possible to obtain a safe and natural antioxidant by enzymatic biotransformation of hardwood hemicellulose.
“Enzymatic bioconversion of beechwood xylan into the antioxidant 2’-O-α-(4-O-methyl-D-glucuronosyl)-xylobiose”. N. Miguez, D. Fernández-Polo, P. Santos-Moriano, B. Rodríguez-Colinas, A. Poveda, J. Jiménez-Barbero, A.O. Ballesteros, F.J. Plou. Biomass Conversion and Biorefinery, published online in September 7th 2022 https://doi.org/10.1007/s13399-022-03240-3.