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Kinetics of SO 2 –ethanol–water (AVAP®) fractionation was determined for sugarcane (SC) straw in terms of pulp composition (non-carbohydrate components, cellulose, hemicelluloses) and properties (kappa number, pulp intrinsic viscosity in CED and cellulose degree of polymerization). Effect of temperature (135–165 °C) and time (18–118 min) was studied at fixed liquor composition (SO 2 /ethanol/water = 12:22.5:65.5, w/w) and a liquor-to-solid ratio (4 L kg −1 ). Interpretation is given in terms of major fractionation reactions, removal of non-carbohydrate components and xylan, as well as acid hydrolysis of cellulose, and is compared to other lignocellulosic substrates (beech, spruce and wheat straw). Overall, SO 2 –ethanol–water process efficiently fractionates SC straw by separating cellulose from both non-carbohydrate components and xylan while reducing cellulose DP. [ABSTRACT FROM AUTHOR]

Lignin and ash material balances of SO 2 -ethanol–water (AVAP®) fractionation of sugarcane (SC) straw were thoroughly studied at various conditions. Most of straw lignin and ash dissolve in the liquor and 40–80% of lignin is precipitated after ethanol removal as a pure (∼99%) and sulfur-lean (<2%) fraction. Most of the acid-soluble ash and its elements (Na, K, Fe, Al) as well as large portion of silica are removed from the fiber phase. Straw lignin behavior exhibited differences compared to wood lignin including high apparent content in fiber, higher degree of sulfonation of dissolved lignin, and dense char-like precipitate formation upon ethanol removal. Variation in fractionation conditions did not have significant effect on lignin properties, while post-sulfonation was capable of changing its form from char-like to colloidal precipitate. [ABSTRACT FROM AUTHOR]

The sulfur balance of SO 2 -ethanol-water (AVAP®) fractionation of sugarcane (SC) straw was investigated. Hydrogen sulfite and sulfite anions are nearly absent in the liquors, despite cations present in straw, whose effect is thus limited to neutralization of lignosulfonic acids decreasing the acidity. Higher degree of sulfonation was observed for dissolved straw lignin compared to wood lignin (0.8–0.9 vs. 0.25 S/C9). Sulfur dioxide amounts of 0.9–1.2, 4.1–4.3 and 44–49 g per o.d. kg straw were bound to pulp, precipitated lignin and lignosulfonic acid, respectively, while the rest of SO 2 was recovered by distillation from the spent fractionation suspensions. [ABSTRACT FROM AUTHOR]

Highlights: [•] Softwood and hardwood biomass is fractionated by SO2–ethanol–water technology. [•] Hemicellulose dissolution rate is similar for softwood and hardwood. [•] Biomass (branches etc.) fractionation is compared with stem wood fractionation. [•] Softwood biomass delignification is inferior likely due to high amount of bark. [ABSTRACT FROM AUTHOR]

The enzymatic hydrolysis of hardwood and softwood harvest residues treated by SO2-ethanol-water (SEW) fractionation was studied. The target was to convert these fibers with high yield into glucose monomers which could be further converted into biofuel by a subsequent fermentation stage. Hardwood biomass residues were efficiently digested at low enzyme dosage (5 FPU/g cellulose) whereas the softwood residues required notably higher enzyme dosage (20 FPU) for sufficient conversion. However, cellulase dosage of softwood could be reduced mannanase supplementation. Especially the high lignin content of softwood biomass pulps impairs the digestibility and thereby, improved delignification could notably enhance the hydrolysis yields. It was shown that inferior delignification of SW biomass is due to persistent polyphenolic acids present in coniferous bark, whereas no evidence of the negative effect of inorganics and acetone extractives was observed. Additionally, SW hydrolyzate was successfully converted into a mixture of butanol, acetone and ethanol through ABE fermentation. [ABSTRACT FROM AUTHOR]

The focus of this study was to find out the effect of bark on SO2–ethanol–water (SEW) fractionation and enzymatic hydrolysis of forest biomass. Softwood bark was found to be more harmful than hardwood bark in both processes. For softwood, the amount of undigested wood in SEW fractionation increased with the increasing bark content, whereas the hardwood bark did not impair the fractionation of wood. The higher the softwood bark content was the lower were the yields in enzymatic hydrolysis likely due to the unproductive binding of enzymes on lignin and other compounds. Addition of surfactant Tween 20 (2% w/w on substrate) prior to enzyme more than doubled the sugar yield of bark-rich softwood pulp. Hardwood bark impaired enzymatic hydrolysis when its share was over 28%. According to a preliminary study, lignosulfonates from the carry-over liquor seem to improve the sugar yield in the enzymatic hydrolysis by acting as a surfactant. [ABSTRACT FROM AUTHOR]

Highlights: [•] Nanofibrils (LCNF) were produced from softwood after SEW fractionation. [•] The effect of lignin and hemicelluloses on LCNF bioconversion was elucidated. [•] Enzyme binding and activity on LCNF was monitored in situ by QCM-D. [•] Hydrolysis of SEW LCNF produce sugar yields higher than those of fibers. [•] SEW-based biorefinery may integrate nanomaterial and biofuel production. [Copyright &y& Elsevier]

Highlights: [•] Oil palm empty fruit bunches (OPEFB) are fractionated by SO2–ethanol–water mixture. [•] Fractionation of OPEFB feedstock produces cellulosic fibers and spent liquor. [•] Spent liquor contains dissolved hemicellulose sugars (mostly monomers) and lignin. [•] Fractionation and sugar hydrolysis is hindered by the high cation content of OPEFB. [•] Acidic leaching of OPEFB only partly removes cations; more intense deashing needed. [Copyright &y& Elsevier]

Abstract: SO2–ethanol–water (SEW) spent liquor from spruce chips was successfully used for batch and continuous production of acetone, butanol and ethanol (ABE). Initially, batch experiments were performed using spent liquor to check the suitability for production of ABE. Maximum concentration of total ABE was found to be 8.79g/l using 4-fold diluted SEW liquor supplemented with 35g/l of glucose. The effect of dilution rate on solvent production, productivity and yield was studied in column reactor consisting of immobilized Clostridium acetobutylicum DSM 792 on wood pulp. Total solvent concentration of 12g/l was obtained at a dilution rate of 0.21h−1. The maximum solvent productivity (4.86g/lh) with yield of 0.27g/g was obtained at dilution rate of 0.64h−1. Further, to increase the solvent yield, the unutilized sugars were subjected to batch fermentation. [Copyright &y& Elsevier]