Invasive biomass valorization: environmentally friendly processes for obtaining second generation bioethanol and saccharides from Ulex europæus.
BACKGROUND: Ulex europiæus (UE) is a widespread invasive shrub species causing economic problems and environmental hazards. This work deals with the valorization of UE by hydrothermal processing (to obtain hemicelluloses-derived saccharides) followed by simultaneous saccharification and fermentation of the resulting solids for manufacturing second generation bioethanol. RESULTS: Hydrothermal processing of UE resulted in the solubilization of up to 21.5 wt% of the oven-dry raw material, leading to the formation of hemicelluloses-derived saccharides as major reaction products. Treatments at various severities resulted in processed solids with enhanced susceptibility to enzymatic hydrolysis, allowing cellulose to glucose conversions up to 87%. Simultaneous saccharification and fermentation of solids pretreated under selected conditions, performed at various charges and solid loadings, resulted in bioethanol conversions up to 82% of the stoichiometric amount, with volumetric concentrations higher than 30 g ethanol L-1. CONCLUSION: Hydrothermal processing of UE followed by simultaneous saccharification and fermentation of pretreated solids was suitable for the selective separation of hemicelluloses as soluble saccharides and for the manufacture of second generation bioethanol at high yield from the pretreated solids.