BACKGROUND: Cytisus scoparius samples were processed with hot, compressed water (autohydrolysis treatments) to obtain both fiber-containing solids (suitable as reinforcements for composites) and a liquid phase containing sugar oligomers derived from hemicelluloses. The solid phase from autohydrolysis, mainly made up of cellulose and lignin, was employed for manufacturing polylactic acid (PLA)-based biodegradable composites. The mechanical properties, water uptake and thermal properties of composites were assessed. RESULTS: The hydrolysis of the major hemicellulose polysaccharide components of Cytisus scoparius was interpreted using kinetic models based on sequential pseudo-homogeneous first-order, irreversible reactions. Operating under non-isothermal conditions, the autohydrolysis experiment carried out at up to 215 degrees C led to the maximum concentration of sugar oligomers (accounting for about 71% of the initial xylan). These compounds can be employed for a variety of purposes, including applications as prebiotics. Composites containing autohydrolyzed fibers presented both improved impact strength and reduced water absorption ability. CONCLUSIONS: Autohydrolysis of Cytisus scoparius led to a liquid phase containing xylooligosacharides with commercial value, and to a solid phase suitable as a reinforcement for PLA-based composites with reduced water retention ability. (C) 2010 Society of Chemical Industry