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Lignin is the most abundant natural aromatic macromolecule in the nature, but its high value-added utilization has been seriously hindered by the highly random and branched structures and the high difficulty in separation and purification. A microwave-assisted ternary deep eutectic solvent (DES) composed by formic acid, lactic acid and choline chloride was developed for lignin pretreatment. The effects of three types of DES on main characteristics of lignin were investigated, and the corresponding dissolution mechanism was proposed. The results showed that, the microwave-assisted ternary DES pretreatment showed an obvious improvement on main characteristics of regenerated lignin, e.g., a higher purity, lower molecular weight with reduced dispersity, improved thermal stability, higher phenolic hydroxyl content, and increased antioxidative activity in comparison with control. It is expected that the lignin macromolecular can be facile regulated and upgraded by the proposed ternary DES., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

An integration of different pretreatments is important to overcome recalcitrance and realize efficient bioconversion of lignocellulosic biomass. This study aims at the effects of combination of hydrothermal pretreatment and different chemi-mechanical pretreatments on enzymatic hydrolysis, and understanding the enzymes adsorption mechanism. The combination of hydrothermal and chemi-mechanical pretreatments effectively improved the enzymatic hydrolysis of poplar substrates, in which the enzymatic hydrolysis of substrates pretreated by hydrothermal pretreatment + Fenton pretreatment + mechanical refining (HFM) was the highest (92.39% of glucose conversion yield, and 20.88 g/L of glucose concentration). The substrates' main characteristics were obviously changed after combined pretreatments, such as swelling ability and specific surface area of substrates were increased. The Langmuir adsorption model (R 2  > 0.98) and pseudo second-order adsorption kinetic model (R 2 ≈1) were well suitable to describe the adsorption of enzymes on substrates, meanwhile the adsorption mechanism was summarized., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Understanding the adsorption behavior and the interaction between substrates and enzymes are critical to improving enzymatic hydrolysis efficiency and reducing bioconversion cost. Herein, the adsorption of cellulase on wet ground corncob residues was studied, and the effects of main characteristics of wet ground corncob residues on adsorption capacity were quantitatively analyzed with the combination of principal component analysis and multiple linear regression models. The results showed that the adsorption of cellulase on wet ground corncob residues was fitted well with Langmuir isotherm adsorption and pseudo second-order kinetics model, the adsorption rate and adsorption capacity were greatly enhanced with increasing grinding time; the multiple linear regression models describing the relationship between main characteristics of corncob residues and adsorption capacity to cellulase were established; the significance of these characteristics were in the following order: average particle size, crystallinity index, specific surface area, surface lignin concentration, water retention value, and surface charge density., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

The combination of different pretreatment methods can effectively overcome recalcitrance of lignocellulosic biomass to ensure its highly efficient conversion into bio-based products. In this study, the combined pretreatments of chemical methods (hydrothermal treatment and Fenton treatment) with mechanical refining were used to improve the enzymatic hydrolysis efficiency of poplar branches. The results indicated that hydrothermal pretreatment and Fenton pretreatment can effectively improve the enzymatic hydrolysis of poplar substrates, e.g., the maximum glucose conversion yield and glucose concentration reached 92.4% and 20.8 g/L, respectively. The pre-hydrolysates contained some valuable components such as monosaccharides, oligosaccharides, acetic acid, furfural, and hydroxymethylfurfural. The main characteristics (specific surface area, water retention value, fines content, and surface lignin concentration) of poplar substrates were obviously changed by the combined pretreatment, which benefit the enzymatic hydrolysis., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Under the situation of increasingly severe challenge of energy consumption, it is of great importance to make full use of bioresources such as forestry and agricultural residues. Herein, the corncob residues generated after processing corncob were enzymatically hydrolyzed to yield fermentable sugars. To overcome the recalcitrance of corncob residues, three kinds of pretreatment methods, i.e., sulfonation, PFI refining, and wet grinding, were applied; their effects on enzymatic hydrolysis and main characteristics of corncob residues substrate were investigated. The results showed that the enzymatic digestibility of the substrate was greatly enhanced by employing each method. The wet grinding exhibited obvious advantages, e.g., the conversion yield of cellulose to glucose and glucose concentration reached 96.7% and 32.2 g/L after 59 h of enzymatic hydrolysis, respectively. The improvement in enzymatic hydrolysis was mainly attributed to the altered characteristics of the substrate such as swelling ability, specific surface area, and particle size and distribution., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Chemi-mechanical pulping, a typical high-yield pulping method, combined with autohydrolysis pretreatment prior to pulping is an efficient and value-added utilization method for biomass in pulp and paper industry. This study investigated the surface lignin changes of poplar sapwood chips in autohydrolysis pretreatment and their effect on the subsequent alkali impregnation for chemi-mechanical pulping. The results showed that the surface lignin content went up with the increase of autohydrolysis intensity, and that the existence of the surface lignin had nearly no impact on the subsequent alkali impregnation in making chemi-mechanical pulps (CMPs) compared to the volume porosity, which was validated by using the stepwise regression analysis. It can be further concluded that autohydrolysis can facilitate the subsequent alkali impregnation of the autohydrolyzed sapwood chips in making CMP, which would be of significance for the combination of biomass refinery and pulp and paper industry., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

This work investigated the changes in the physical structure of autohydrolyzed poplar sapwood chips and the effect on the subsequent alkali liquor diffusion properties for chemi-mechanical pulping (CMP). An alkali impregnation process was conducted by using the autohydrolyzed poplar sapwood with different levels of autohydrolysis intensity. The results showed that the volume porosity, water constraint capacity, and saturated water absorption of the autohydrolyzed poplar sapwood chips increased. Also, the effective capillary cross-sectional area (ECCSA) in the radial direction and the diffusion coefficients of NaOH solution in both the radial and axial directions all increased. Autohydrolysis pretreatment enhanced the alkali liquor diffusion properties in poplar sapwood chips, and the diffusion coefficient was increased more greatly in the radial direction than that in the axial direction., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Dilute acid pre-extraction enhanced the mechanically refined poplar pulp substrates' enzymatic hydrolysis efficiency obviously. The results showed that the surface lignin distribution was changed significantly in residual wood chips and pulp substrates, and the surface lignin distribution showed important impact on the following enzymatic hydrolysis. Acid pre-extraction can lead to a redistribution of lignin in fiber cell walls, i.e., the lignin was degraded and migrated to fiber surface in the form of re-deposited lignin and pseudo-lignin. However, higher pre-extraction intensity was not desired due to the formation of redeposited lignin and pseudo-lignin. This study will help to reach a deeper understanding on the lignin distribution in the view of molecular and ultrastructure, and promote the development of a cost-efficient pretreatment strategy for biomass processing., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

This work is aimed at investigating the influence of changes in the content of hemicelluloses of the autohydrolyzed poplar sapwood on the subsequent alkali impregnation for chemi-mechanical pulping (CMP). An alkali impregnation process was conducted using the autohydrolyzed poplar sapwood with different content of hemicelluloses as raw materials. The results showed that both the amount of NaOH consumption and swelling degree of poplar sapwood increased with the removal of hemicelluloses, thus enhancing the alkali impregnation effectiveness. The hemicelluloses removal can also shorten the alkali impregnation time for the autohydrolyzed poplar sapwood to achieve the similar impregnation effectiveness of unautohydrolyzed poplar sapwood. All of these can be attributed to the fact that the hemicelluloses removal would result in the exposure of more free hydroxyl groups on the cellulose and an increase in the porosity of the fiber cell walls., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Autohydrolysis with different severity factors was performed on poplar wood chips prior to pulping, and the wettability, absorbility and the following impregnation of NaOH solution for the poplar wood chips were then investigated. The results showed that after autohydrolysis pretreatment the porosity, shrinkage and fiber saturation point (FSP) of the poplar wood chips were increased, while the surface contact angle decreased as the severity factor was increased. The autohydrolyzed chips absorbed more NaOH in impregnation that resulted in a low NaOH concentration in the bulk impregnation liquor (i.e., the impregnation liquor outside wood chips), while the concentration in the entrapped liquor (i.e., the impregnation liquor inside wood chips) was increased. Autohydrolysis substantially improved the effectiveness of alkali impregnation., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

The hardwood bleached kraft pulp (HBKP) fibers were pretreated by PFI mill to obtain the substrates, the effects of fibrillation on HBKP fibers' enzymatic hydrolysis was studied. The results showed that the enzymatic hydrolysis efficiency was enhanced obviously by mechanical refining. The mechanical refining alterated the fibers' characteristics such as fibrillation degree, specific surface area, swelling ability, crystallinity, fiber length and fines content. All these factors correlating to the enzymatic hydrolysis were evaluated through mathematical analysis. Among these factors, the fibrillation degree has the profoundest impact on the enzymatic hydrolysis of wood fibers. Consequently, the mechanical refining aiming for a high fibrillation degree was feasible to enhance the enzymatic hydrolysis of lignocellulosic biomass., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Autohydrolysis pretreatment with different severity factors was performed on poplar chips prior to chemi-thermomechanical pulping (CTMP) in order to investigate the change in pH value and its effect on the autohydrolysis pretreatment. The results showed that the dissolution amount of acetic acid increased with raising the severity factor of the pretreatment and declining the size of poplar chips, respectively. Besides, a logarithmic relationship between the amount of acetic acid released in the autohydrolysis liquor (AHL) and pH value of the AHL was observed. The amounts of glucose and xylose (including those in the form of monomers, oligomers, and polysaccharides) as well as furfural and hydroxymethylfurfural (HMF) also depended on the pH value of the AHL to some extent., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Three different pre-extraction methods (i.e., acetic acid, sulfuric acid and sodium hydroxide) were used for the pretreatment followed by chemi-thermomechanical treatments and then enzymatic hydrolysis of wheat straw to produce fermentable sugars. The performance of enzymatic hydrolysis by the synergistic effect of pre-extractions and chemi-thermomechanical treatments was remarkable. Results showed that the pre-extraction combining with the chemi-thermomechanical treatments shorten the enzymatic hydrolysis time and improved the glucose yield at the same enzyme loadings. The chemical components, swelling ability, and crystallinity, as well as the surface morphology of the substrates were changed obviously. All of these changes can affect the accessibility of enzymes to cellulose in the substrates to a certain extent., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

This study investigated the autohydrolysis pre-treatment prior to chemi-thermomechanical pulping (CTMP) process including the effects of autohydrolysis pretreatment with a lower severity on characteristics of the autohydrolysis liquor and hydrolyzed chips. The intensity of autohydrolysis, characterized by the severity factor, increased from 1.76 to 3.54, the hydrolyzed chips yield decreased from 99.0% to 86.7% and the xylose extraction yield increased from 0.8% to 44.0%. The content of holocellulose, pentosan and acid soluble lignin remained in the hydrolyzed chips decreased dramatically with increasing the treatment severity. After the autohydrolysis pretreatment, the resultant poplar chemi-thermomechanical pulp with a severity factor of 2.37 could obtain a 15.3 Nm/g tensile index, 58.6% ISO brightness and a 2.39 cm(3)/g bulk., (Copyright © 2014 Elsevier Ltd. All rights reserved.)