Fractionation of Hemicelluloses and Lignin from Rice Straw by Combining Autohydrolysis and Optimised Mild Organosolv Delignification

Abstract

An integrated strategy was followed to valorise rice straw, one of the most relevant biomass feedstocks available worldwide, to selectively recover solubilised hemicelluloses and lignin. The pathway encompassed the use of autohydrolysis to hydrolyse the hemicelluloses and an ethanol-based organosolv process to solubilise lignin. Several autohydrolysis conditions were assayed with the best results obtained at 210 ºC (log R0 4.15), which enabled high removal of hemicelluloses, yielding an oligosaccharide-rich hydrolysate and a treated biomass with low content of hemicelluloses and enriched in cellulose and lignin. The effects of ethanol concentration (5 to 75%), and reaction time (0 to 24 h) on lignin removal under mild temperature (30 ºC) were studied. In optimal conditions (60.5% ethanol, 24h) the delignification yield reached 42%, whereas glucan solubilisation was below 17%. Lignin solubilisation yield was not influenced by the organosolv treatment duration while ethanol concentration favored the delignification up to 60.5% ethanol. The organosolv liquors contained economic interesting ligninderived compounds such as vanillin, ferulic, and coumaric acids. The chemical composition and enzymatic digestibility of the treated biomass from autohydrolysis and organosolv delignification were compared, with the latter presenting an almost 10% higher enzymatic digestibility than the former.

Autohydrolysis of Annona cherimola Mill. seeds: Optimization, modeling and products characterization

“…it is significantly higher than the glucose yieldreported for eucalyptus residues (54%), and close to 82% for olive tree pruning, and only slightly lower for straws (88, 90 and 91 %, respectively for rice, corn straw and wheat straw) [37][38][39], what may be explained by the higher lignin content of the cherimola seed cake as compared to straws.Although, it is reported that the highest glucose yield can only be achieved after the complete removal of hemicellulose, the lignin also plays a role on preventing cellulose hydrolysis that must not be neglected [22].…”

Chemical characterization of the bark ofEucalyptus urophyllahybrids in view of their valorization in biorefineries

“…A hydrothermal treatment could be considered for removal of hemicelluloses and could give rise to oligosaccharides (Moniz et al 2013(Moniz et al , 2014. Delignification via solvolysis (Moniz et al 2015) would yield organosolv lignin in solution and a solid fraction of cellulose. A schematic potential valorization design is given in Figure 1 showing potential estimates of maximal yields for the different products.…”

Bark Characterisation of the Brazilian Hardwood Goupia glabra in Terms of Its Valorisation

“…In the case of G. glabra bark, the high content of polar extractives motivates their removal and valorisation as a first step in the conversion process, while the high content of lignin could be of interest for, e.g., biofuel production, and the xylans can be a source of xylo-oligosaccharides and other sugars (Moniz et al 2013(Moniz et al , 2014(Moniz et al , 2015.…”