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Highlights: [•] Redistribution of chemical compositions occurs during the process of size classification. [•] Glucan conversion is affected synthetically by the augment of surface area, lignin enrichment, and cellulose decrystallization that accompany with the process of size reduction. [•] Diversity of woody recalcitrance in bioconversion is reflected by the distinguishing responses of enzymatic digestibility to size reduction. [Copyright &y& Elsevier]

Bamboo chips were efficiently fractionated using an integrated process of autohydrolysis and formic acid to induce rapid delignification. Autohydrolysis pretreatment facilitated oligosaccharide production, while the subsequent rapid-delignification using formic acid at a low liquid/solid ratio with a relatively short reaction time allowed obtaining cellulose fibers and lignin. The major inter-unit linkages of side-chain in lignin were cleaved during the combined fractionation process. The lignin fraction exhibited higher purity, more phenolic OH groups, less condensed phenolic OH groups, and higher syringyl/guaiacyl ratio (S/G) as compared to MWL and formic acid lignin from the direct formic acid delignification. These results indicate that the combined fractionation process presents a promising approach to the commercial utilization in the biorefinery industry. [ABSTRACT FROM AUTHOR]

Bamboo was fractionated using formic acid based on a one-step organosolv process under high pressure (at 145 °C for 45 min, 0.3 MPa) and at atmospheric pressure (at 101 °C for 120 min), respectively. High-pressure formic acid lignin, atmospheric formic acid lignin and milled wood lignin of bamboo were subjected to comprehensive structural characterization using gel permeation chromatography (GPC), Fourier transform infrared (FTIR) and solution-state NMR techniques ( 1 H, 13 C, 2D-HSQC, and 31 P-NMR spectroscopies). The results indicated that the formic acid fractionation under high pressure presents a quick and efficient delignification method by enhancing the cleavage of interunitary bonds in lignin (β-O-4′, β-β and β-5′), and dissolved lignin also occurred condensation reaction. As compared to atmospheric formic acid lignin, high-pressure formic acid lignin obtained showed higher purity and yield, and had relatively higher contents of phenolic and carboxylic groups. [ABSTRACT FROM AUTHOR]

In analogue to the biorefinery concept, the separation process of lignocellulosic biomass is the most critical step to obtain its main components, namely cellulose, hemicelluloses and lignin. Moreover, the applied fractionation approach has a decisive impact on the characteristics and subsequent valorization strategies of the distinguished fractions. This review presents the state of art of novel biomass fractionation processes that are recently developed and focusing on autohydrolysis, organosolv fractionation, ionic liquid and deep eutectic solvent (DES) treatment. Moreover, the facing challenges, perspectives and future development direction in the field of fractionation of lignocellulosic biomass are discussed. The purpose of this review is to provide inspiration and guidance for fractionating biomass with environmentally friendly and efficient pathways, thus to push forward their further industrialization based on the integrated biorefinery concept. [Display omitted] • Green fractionation of biomass is a necessary process for biorefinery. • The recent advance of the leading fractionation technologies were reviewed. • The critical technical challenges for the discussed fractionation approaches were proposed. • The perspectives and future development direction of biomass fractionation were presented. • Fractionation processes should be upgraded to meet the industrialization requirements. [ABSTRACT FROM AUTHOR]

Ethanol extraction of lignocellulosic biomass under mild conditions has re-attracted considerable attention since a light-colored lignin with low molecular weight can be obtained. Unfortunately, the yield of isolated lignin for the ethanol extraction process is very limited. To enhance the extraction efficiency of lignin from poplar, ultrasound was used to assist the ethanol extraction and the isolated lignin was analyzed in terms of structure features and functional properties. As expected, increasing the ultrasonic power and ultrasonic time led to higher lignin yields during the ultrasound-assisted ethanol extraction (UAEE) process. The chemical structure of the isolated lignin (UAE-L) was almost completely retained, the C-O (mainly β-O-4) linkages in the lignin only exhibited a slight decrease, while the C-C (β-β, β-5, and β-1) linkages were nearly unchanged. The UAE-L was light in color and had more phenolic hydroxyl groups, less carbohydrate impurities, lower molecular weight and narrower polydispersity as compared to the poplar MWL. The UAE-L could scavenge more 2,2-diphenyl-1-picrylhydrazyl radicals (DPPH·), displaying a stronger antioxidant activity. Moreover, the UAE-L showed good UV-absorbing properties in both UVA and UVB regions. These results indicated that the UAE-L has great potential for replacing the commercial synthesized antioxidant and anti-UV ingredients. The overall scheme of the isolation process of lignin from poplar by ultrasonic-assisted ethanol extraction (UAEE). [Display omitted] • Ultrasound was employed to enhance ethanol extract of lignin. • Light-colored lignin with abundant phenolic -OH and low molecular weight was obtained. • Lignin unit with less ortho- methoxy substitutions was preferentially released. • UAE-L showed good antioxidant activity and broad-spectrum UV-absorption capacity. [ABSTRACT FROM AUTHOR]

[Display omitted] • Lignin recovery from PHL and adsorbent preparation was achieved in one step. • The lignin was modified and recovered from PHL via HRP treatment. • Lignin recovered from PHL by HRP treatment was a good adsorbent for MB removal. • The maximum MB adsorption capacity of EML was 241.1 mg/g at 308 K. The lignin in PHL could be modified and recovered from pre-hydrolysis liquor (PHL) by horseradish peroxidase (HRP) treatment. The enzyme-modified lignin (EML) separated from PHL was used to adsorb and remove methylene blue (MB) from a model dye effluent; the adsorption performance of EML was studied. The results indicated the carboxyl content of the lignin in PHL increased by HRP treatment, and the EML removed from PHL had a carboxyl content of 0.69 mmol/g and a BET surface area of 25.6 m2/g. With the increase of pH, the adsorption capacity of EML obviously increased. The maximum MB adsorption capacity of EML was 210.2 mg/g and 241.1 mg/g at 298 K and 308 K, respectively. The fitting results revealed that the equilibrium adsorption isotherms and adsorption kinetics followed the Langmuir model and pseudo-second-order model, respectively. [ABSTRACT FROM AUTHOR]