Hemicellulose extract from Cynara cardunculus: a source of value-added biomolecules produced by xylanolytic thermozymes

Cynara cardunculus hemicellulose fraction was recovered from its stems and leaves biomass and converted in valuable molecules by exploiting the extracellular xylanase and ?-xylosidase activities produced by the thermophilic bacterium Geobacillus thermantarcticus. Several degradation procedures of the arabinoglucuronoxylan extract were proposed by using efficient and different enzymatic preparations, containing both or only one xylanolytic activity of G. thermantarcticus. In particular, when the xylanase and ?-xylosidase activities were used separately into hydrolysis reactions, xyloglucurono-oligosaccharides or xylose were obtained with a yield of 32% and 62.6 % respectively, with reference to hemicellulosic extract. Furthermore, the synergic action of beta-xylosidase/xylanase activities were exploited in transglycosyaltion processes for the production of xylo-conjugated; xylosides of primary alcohols with increasing carbon chains and aromatic alcohols were produced starting from the C. cardunculus hemicellulose, which was selected as cheap donor. When 2-phenoxyethanol was selected as acceptor, 2-phenoxyethyl beta-xyloside, xylobioside and xylotrioside were prepared with a yield of 38.5 % with respect to hemicellulosic extract and spectroscopically characterized.