An integrated olive stone biorefinery based on a two-step fractionation strategy

Olive stones (OS) constitute a waste lignocellulosic material produced by the olive oil industry in great amounts, that currently is only used as low-value energy source for industrial or domestic boilers. Having view its full valorization, this work proposes and validates an integrated strategy aiming to obtain three different streams of sugars / lignin-derived compounds. Dilute acid hydrolysis was xylose-rich hydroysate chemically converted into furfural with 48.7 % yield. The resulting acid-pretreated solid biomass consisted mainly lignin cellulose, subjected catalyzed ethanol-based organosolv delignification. Temperature, time, sulphuric concentration were optimized order recover added-value products digestible cellulose. At optimal conditions (190 ?C 30 min), 50 delignification reached, together highest enzymatic yields g glucose/kg OS). Phenolic compounds content liquors reached 41.6 mg GAE/g OS. This extract presented antioxidant capacity up 10.9 TE/g pretreated fraction substrate ethanol production pre-saccharification simultaneous saccharification fermentation process, enabling 47 g/L, yield 61.4 theoretical maximum. Globally, from 100 kg OS processed according experimental scheme, 6.9 furfural, 6.2 ethanol, 7.4 lignin, 4.2 phenolics can be obtained main products, thus constituting way valorization renewable multiproduct biorefinery strategy.