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Thermoanaerobacterium aotearoense SCUT27 is a prominent producer of biofuels from lignocellulosic materials. To provide sufficient NAD(P)H for ethanol production, redox-related genes, including lactate dehydrogenase (ldh), redox-sensing transcriptional repressor (rex), and hydrogenase (hfsB), were knocked out. However, the growth of strain PRH (Δldh/Δrex/ΔhfsB) was suppressed due to the intracellular redox state imbalance with the increased NADH concentration. Coincidentally, when the Bcd-EtfAB (BCD) complex was overexpressed, the resulting strain PRH-B3 (Δldh/Δrex/ΔhfsB::BCD) grew rapidly and produced ethanol with a high yield. With lignocellulosic hydrolysates, PRH-BA (Δldh/Δrex/ΔhfsB::BCD::adhE) demonstrated high ethanol productivity and yield, reaching levels of 0.45-0.51 g/L/h and 0.46-0.53 g/g sugars, respectively. The study results shed light on the cofactor balance for cell stability and the high ferredoxin-NAD + reductase activity of the BCD complex under an intracellular low redox state. They also provide an essential reference for developing strains for improved biofuel production., 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 © 2024 Elsevier Ltd. All rights reserved.)

This study reports the cellulo-xylanolytic cocktail production from Hypocrea lixii GGRK4 using multi-objective genetic algorithm-artificial neural network tool, resulting in 8.32 ± 1.07 IU/mL, 51.53 ± 3.78 IU/mL activity of CMCase and xylanase, respectively with more than 85 % residual activity at 60 °C and pH 6.0. Interestingly, metal ions viz. K + and Ca 2+ stimulated the enzyme activity, whereas Fe 2+ and Cu 2+ reduced the activity. Significant amounts of hydrophobic compounds, chromophores, and phenolics were released after wastepapers deinking. The deinking efficiency of 73.60 ± 2.45 % and 38.60 ± 1.34 % was obtained for photocopier paper and newspaper, respectively, whereas brightness of 89.90 ± 2.10 % ISO and 44.90 ± 1.63 % ISO was reported for both types of waste papers. The physical strength of deinked photocopier paper and newspapers, i.e., tensile index (3.10 and 0.50 %), tearing index (7.10 and 4.83 %), and burst factor (8.61) were enhanced whereas double fold property was decreased proving wastepaper reusability. This consortium showed effective and significant enzymatic deinking efficiency for recycled wastepapers., 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 © 2024 Elsevier Ltd. All rights reserved.)

Hardwood kraft lignin from the pulping industry is burned or discarded. Its valorization was conducted by subjecting fractionation, amination with ethylenediamine, diethylenetriamine, and monoethanolamine, and crosslinking with formaldehyde or glyoxal to obtain bio-based wood adhesives. Acetone-soluble and insoluble hardwood kraft lignin were prepared and subjected to amination and then crosslinking. Fourier transform infrared, 13 C NMR, 15 N NMR, and X-ray photoelectron spectroscopy results revealed successful amination with amide, imine, and ether bonds and crosslinking of all samples. Hardwood kraft lignin aminated with diethylenetriamine/ethylenediamine and crosslinked using glyoxal exhibited excellent results in comparison with samples crosslinked using formaldehyde. Acetone-insoluble hardwood kraft lignin aminated and crosslinked using diethylenetriamine and formaldehyde, respectively, exhibited excellent adhesion strength with plywood, satisfying the requirements of the Korean standards. The amination and crosslinking of industrial waste hardwood kraft lignin constitute a beneficial valorization method., 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 © 2024 Elsevier Ltd. All rights reserved.)

The heavy metals, pesticides and dyes in agriculture and industry caused serious water pollution have increased the urgency for the advancement of biomass-based adsorbents due to their merits of low cost, high efficiency, and environmental sustainability. Thus, this review systematically examines the recent progress of lignin-based adsorbents dedicated to wastewater purification. Commencing with a succinct exposition on the intricate structure and prevalent forms of lignin, the review proceeds to expound rational design strategies tailored for lignin-based adsorbents coupled with adsorption mechanisms and regeneration methods. Emphasis is placed on the potential industrial applications of lignin-based adsorbents, accentuating their capacity for recovery and direct utilization post-use. The future challenges and outlooks associated with lignin-based adsorbents are discussed to provide novel perspectives for the development of high-performance and sustainable biosorbents, facilitating the effective removal of pollutants and the value-added utilization of resources in a sustainable manner., 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 © 2024. Published by Elsevier Ltd.)

The rational use of bamboo to make dissolving pulp can offer up new opportunities for cellulose production, alleviating wood scarcity. Bamboo contains a high content of non-fiber cells, which presents technical challenges in dissolving pulp production by the conventional process. In this study, a process concept of separating hemicelluloses is presented by fiber fractionation and purification for cleaner production of bamboo dissolving pulp: bamboo kraft pulp was fractionated into long-fiber and short-fiber fractions. The cellulose-rich long-fiber fraction was converted to dissolving pulp by further purification treatment with acid hydrolysis and cold caustic extraction. The hemicellulose-rich short-fiber fraction was used for papermaking. The laboratory results were confirmed by those from mill trials. The combined pulp yield (dissolving pulp + paper-grade pulp) reached 49 %, which was significantly higher than that of the conventional pre-hydrolysis kraft pulping process. Furthermore, the quality of dissolving pulp was higher due to inherently higher cellulose content of long-fiber fraction., 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 © 2024. Published by Elsevier Ltd.)

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.)

Microalgae present a viable mechanism for purifying aquatic environments through the absorption of organic pollutants. In this paper, Chlorella protothecoides was cultured in a tetracycline environment, and biochar was added during the cultivation process. Compared with conventionally cultured Chlorella protothecoides, the addition of biochar for cultivation under a tetracycline environment increased the biomass of Chlorella protothecoides by 13.26 %. Moreover, the adsorption of tetracycline by biochar alone was not complete, but when mixed with Chlorella protothecoides, tetracycline was completely removed, which proved the biosorption of Chlorella protothecoides for low concentrations of tetracycline. Finally, the cultured Chlorella protothecoides was used further to prepare electrode materials, and it was found that the specific capacitance of the material reached 233.15F/g at a current density of 1 A/g. In this study, the use of biochar and Chlorella protothecoides to jointly adsorb tetracycline is of great significance for environmental protection and microalgae cultivation., 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.)

The electrochemical performances and denitrification efficiency of microbial fuel cells (MFCs) are often limited by chemical oxygen demand/nitrogen (COD/N) of wastewater. To overcome this limitation, single-chamber air cathode MFCs with varying COD/N (16/1, 8/1, and 4/1) were established to investigate their electrochemical performances, denitrification efficiency, and bacterial communities. The optimal COD/N for maximizing electricity generation and denitrification efficiency was 8/1, as supported by the greatest corrected coulomb efficiency (13.6%) and electron transfer rate (2.36 C/h for electricity generation, 39.77 C/h for denitrification). As COD/N decreased, the electrochemically active genus Geobacter was replaced by the denitrifying genera Un._f_Burkholderiaceae, Dechlorosoma, and Petrimonas. These results indicated that the efficiency of electricity generation and denitrification was not solely determined by the abundance of electrochemically active and denitrifying bacteria. The presence of a faster electron transfer pathway, possibly direct interspecies electron transfer, enhanced simultaneous electricity generation and denitrification in MFCs with COD/N of 8/1., 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.)

The failure of hemicellulose valorization in a deep eutectic solvent (DES) pretreatment has become a bottleneck that challenges its further development. To address this issue, this study developed a DES/GVL (γ-valerolactone) biphasic system for effective hemicellulose-furfural conversion, enhanced cellulose saccharification and lignin isolation. The results indicated that the biphasic system could significantly improve the lignin removal (as high as 89.1%), 86.0% higher than the monophasic DES, accompanied by ∼100% hemicellulose degradation. Notably, the GVL in the biphasic solvent restricted the condensation of hemicellulose degradation products, which as a result generated large amount of furfural in the pretreatment liquid with a yield of 68.6%. With the removal of hemicellulose and lignin, cellulose enzymatic hydrolysis yield was boosted and reached near 100%. This study highlighted that the novel DES/GVL is capable of fractionating the biomass and benefiting their individual utilization, which could provide a new biorefinery configuration for a DES pretreatment., 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.)

This work aimed to study an integrated pretreatment technology employing p-toluenesulfonic acid (TsOH)-catalyzed liquid hot water (LHW) and short-time ball milling for the complete conversion of poplar biomass to xylooligosaccharides (XOS), glucose, and native-like lignin. The optimized TsOH-catalyzed LHW pretreatment solubilized 98.5% of hemicellulose at 160 °C for 40 min, releasing 49.8% XOS. Moreover, subsequent ball milling (20 min) maximized the enzymatic hydrolysis of cellulose from 65.8% to 96.5%, owing to the reduced particle sizes and cellulose crystallinity index. The combined pretreatment reduced the crystallinity by 70.9% while enlarging the average pore size and pore volume of the substrate by 29.5% and 52.4%, respectively. The residual lignin after enzymatic hydrolysis was rich in β-O-4 linkages (55.7/100 Ar) with less condensed structures. This lignin exhibited excellent antioxidant activity (RSI of 66.22) and ultraviolet absorbance. Thus, this research suggested a sustainable waste-free biorefinery for the holistic valorization of biomass through two-step biomass fractionation., 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.)

This study reported that surfactants could facilitate the organosolv pretreatment of lignocellulosic biomass (LCB) to produce fermentable sugars and highly active lignin. Under the optimized conditions, the surfactant-assisted glycerol organosolv (saGO) pretreatment achieved 80.7% delignification with a retention of 93.4% cellulose and 83.0% hemicellulose. The saGO pretreated substrate exhibited an excellent enzymatic hydrolyzability, achieving 93% of glucose yield from the enzymatic hydrolysis at 48 h. Structural analysis showed that the saGO lignin contained rich β-O-4 bondings with less repolymerization and lower phenolic hydroxyl groups, thus forming highly reactive lignin fragments. The analysis evidenced that the surfactant graft the lignin by structural modification, which was responsible for the excellent substrate hydrolyzability. The co-production of fermentable sugars and organosolv lignin almost recovered a gross energy (87.2%) from LCB. Overall, the saGO pretreatment holds a lot of promise for launching a novel pathway towards lignocellulosic fractionation and lignin valorization., 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.)

Deep eutectic solvents (DESs) with different acidity and alkalinity were applied for biomass pretreatment, and the conditions were optimized by response surface methodology. The results showed that lactic acid/betaine hydrochloride had the optimal pretreatment efficiency, where the removal rates of hemicellulose and lignin came up to 89% and 73%, and the enzymolysis efficiency was as high as 92%. Furthermore, eight types of chloride salts with different valence states were introduced into the DESs as the third component. The chloride salts could improve the pretreatment efficiency and positively correlated with the metal valence state. Specifically, AlCl 3 was significantly superior in improving the pretreatment efficiency, where the enzymolysis efficiency reached 96% due to the destruction of crystalline region and the esterification of partial cellulose. Therefore, it is proposed that adding highly valent metal salts to acidic DESs has higher pretreatment and enzymatic efficiency., 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.)

Developing an environmentally friendly and efficient pretreatment to utilize wheat straw is essential to a sustainable future. An acid biphasic system with 2-methyltetrahydrofuran (2-MeTHF) organic solvent and dilute p-toluenesulfonic acid (p-TsOH) were employed for the simultaneous fractionation of three components. Results showed that the biphasic system had excellent cellulose protection and high removal of hemicellulose and lignin. In detail, Under the optimal conditions (0.1 M p-TsOH, 2-MeTHF: H 2 O = 1:1 (v:v), 140 °C, 3 h), mostly cellulose retained in the residues (95.69%), 57.18% of lignin was removed and high yield of hemicellulose-based C5 sugars was achieved (77.49%). In the further process of dehydration of pre-hydrolysate dichloromethane (DCM) as an organic phase, the yield of furfural was 80.07% (170 °C-80 min). The saccharification of residue reached 95.82%. p-TsOH/2-MeTHF/H 2 O pretreatment was desirable for high selectivity fractionation. Important chemicals for bioenergy including furfural, monosaccharides and lignin are obtained., 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. Published by Elsevier Ltd.)

Here, a Cu 2+ -doped lignin-based adsorbent (Cu-AL) was fabricated via the amination and Cu 2+ -doping of industrial alkali lignin for massive and selective adsorption of cationic dyes azure B (AB) and saffron T (ST). The Cu-N coordination structures endowed Cu-AL with stronger electronegativity and higher dispersity. Through the electrostatic attraction, π-π interaction, H-bonding, and Cu 2+ coordination, the adsorption capacities of AB and ST reached up to 1168 and 1420 mg g -1 , respectively. The pseudo-second-order model and Langmuir isotherm model were more relevant to the AB and ST adsorption on Cu-AL. Based on the thermodynamic study, the adsorption progresses were endothermic, spontaneous, and feasible. The Cu-AL maintained high removal efficiency to dyes after 4 reuses (>80%). Importantly, the Cu-AL could efficiently remove and separate AB and ST from dye mixtures even in real time. All the above characteristics demonstrated that Cu-AL was an excellent adsorbent for fast wastewater treatment., 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.)

Lignocellulose can be converted into biofuel or functional materials to achieve high value-added utilization. Biomass utilization process is complex and multi-dimensional. This paper focuses on the biomass conversion reaction conditions, the preparation of biomass-based functional materials, the combination of biomass conversion and traditional wet chemistry, molecular simulation and process simulation. This paper analyzes the mechanism, advantages and disadvantages of important machine learning (ML) methods. The application examples of ML in different aspects of high value utilization of lignocellulose are summarized in detail. The challenges and future prospects of ML in this field are analyzed., 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 © 2022. Published by Elsevier Ltd.)

Biodiesel is a typical renewable energy and the previous transesterification processes for biodiesel production mainly focus on thermocatalytic methods. In this paper, the ball-milling process was investigated into the biodiesel production under Kraft lignin activated carbon stabilized K 2 CO 3 . Biodiesel yield increased to 66 % after only 5 min and reached 100 % within 25 min under optimal ball-milling conditions (0.5 g of the catalyst; methanol/oil molar ratio 18:1; 195 g of ball-mill beads; 1400 rpm; 25 °C). The power demand between the thermocatalytic method and the ball-milling method was also compared. Based on the computation, the ball-milling method has lower power demand than the traditional method (38 vs 201 kWh·mol -1 ). Therefore, the ball-milling method is an effective and economical process for biodiesel production., 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 © 2022 Elsevier Ltd. All rights reserved.)

Tandem strategy for lignin utilization with photocatalytic preoxidation and ultrasonic cavitation depolymerization was proposed. Cornstalk residual lignin from industrial bioethanol process was first photocatalytically preoxidized under visible light by g-C 3 N 4 and WO 3 /g-C 3 N 4 /h-BN (WCB) photocatalysts respectively, then obtained lignin samples were characterized to confirm the preoxidation with raw lignin as a blank. During photocatalytic preoxidation, benzyl hydroxyls in lignin was transformed to carbonyls, but a certain degree of lignin degradation and condensation was observed. In comparison, WCB-catalyzed photopreoxidation was more effective. Thereafter, lignin depolymerization was achieved by ultrasonic cavitation-assisted ethanololysis under optimal conditions. Compared with the mere ultrasonic cavitation depolymerization of pristine lignin, WCB-induced photocatalytic preoxidation improved the conversion rate by 14%, the light-oil yield by 26%, and the phenolic monomer yield by 35%. In general, the reported tandem method worked very well for the enhancement of lignin depolymerization and provided a new idea for the development of lignin valorization., 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 © 2022 Elsevier Ltd. All rights reserved.)

The selectivity of alkali treatment (AT) for hemicellulose separation is reduced due to the alkali solubility of lignin. It was improved using freeze-thaw-assisted alkaline treatment (FT/AT). In this study, bamboo hemicellulose was separated via a one-step freeze-thaw-assisted alkali treatment (OFT/AT). The effects of freezing temperature, freezing time, alkali concentration, and treatment time on bamboo components were studied. The separation yield of hemicellulose was 73.26%, compared to 64.00% using conventional FT/AT. The separation of lignin and cellulose was inhibited as alkali concentration decreased from 7.0% to 5.0%. The extraction yield of hemicellulose increased from 46.35% to 56.12%. Structural analysis of extracted hemicellulose revealed the effective inhibition of the breakage of the xylose backbone and arabinose side chain of hemicellulose. This indicated that the molecular structure of extracted hemicellulose was relatively complete. It provides theoretical support for the efficient separation of hemicellulose by AT., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

This study adopted the combination of activated sludge treatment and catalytic ozonation technology to efficiently remove the high concentration of ammonia nitrogen from landfill leachate. Through optimizing the parameters continuously, the COD, NH 4 + -N, UV 254 and colority respectively descended to 417.75 ± 6.72 mg/L, 9.77 mg/L, 1.98 ± 0.04 and 40 times, and 3D fluorescence also reduced significantly within 14 days. Target genes of AOB-amoA, nxrA, napA, nirS and nosZ analysis indicated that ammonia-oxidizing bacteria, nitrated bacteria, and denitrifying bacteria played a key role on nitrogen removal, aerobic denitrifying bacteria was dominated especially. The nitrogen removal process was as follows: catalytic ozonation converted nitrogen-containing organic matter into NH 4 + -N, then NH 4 + -N was converted into NO 2 - -N and NO 3 - -N with the action of ammonia oxidation, nitrification and catalytic ozonation. Finally, the denitrification microorganisms transformed NO 3 - -N or NO 2 - -N to N 2 . Therefore, this coupled process realized the nitrogen removal effectively from landfill leachate., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Microwave technology is utilized to prepare porous carbon from the chili straw pyrolysis residue in this study. As the pyrolysis temperature increases, the thermal stability of biochar is higher. The carbon speciation of the porous carbon PC500 is closest to that of graphite, and its inorganic-C reaches to 51.21%. Notably, the specific surface area of the activated porous carbon increases with increasing pyrolysis temperature, with a maximum value of 2768.52 m 2 /g for PC500. Further testing of the electrochemical properties of the porous carbon, PC500 possesses a high specific capacitance of 352F/g at 1 A/g while that of conventional heating is only 226.1F/g. The porous carbon prepared by microwave heating has better electrical properties compared to conventional heating, and the biochar obtained at higher pyrolysis temperature has a richer pore structure after activation., (Copyright © 2022. Published by Elsevier Ltd.)

A choline chloride-formic acid (ChCl-FA) pretreatment followed by enzymatic hydrolysis and fermentation were developed in this work for co-produce bioethanol, xylose, and lignin from eucalyptus. Results showed that ChCl-FA pretreatment can simultaneously degrade the xylan (∼95.2%) and lignin (∼74.4%) in eucalyptus, and obtained the pretreated eucalyptus having high glucan content and a numbers of cracks and holes, which was conducive to follow-up cellulase attacking. The hydrolysis experiments showed the maximum yield of glucose of 100 g eucalyptus was 35.3 g, which was equivalent to 90.3% of glucan in eucalyptus feedstock. The fermentation of enzymatic hydrolysate finally achieved the ethanol yield of 16.5 g, which corresponded to 74.5% theoretical ethanol yield from initial glucan in eucalyptus. In addition, 12.1 g xylose and 23.9 g lignin also could be obtained in pretreated liquid or/and hydrolysis residue, which represented for 61.4% xylan and 80.7% lignin in eucalyptus feedstock, respectively., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

The complexity of polysaccharide hydrothermal products increases the difficulty of exploring the formation of biochar, limiting the development of biochar. This work clarifies the completive effects of glucan's main hydrolysates on biochar formation from three aspects: experimental, thermodynamic, and kinetic. The products distribution illustrates that 5-HMF, FA, and LA are mainly involved in the formation of biochar. Biochar mainly includes furan ring, ether group, and ester group by the analysis of magic-angle-spinning nuclear magnetic resonance, X-ray photoelectron spectroscopy, and elemental analysis. Combined experiments and density functional theory analysis, the etherification reaction of 5-HMF itself is most likely to occur and is key to form biochar, followed by the esterification of FA with 5-HMF, and then the etherification of 5-HMF and LA. The further verified experiments also manifest these results. This work will develop a foundation for exploring the complex formation mechanism of cellulose-based biochar., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Clostridium tyrobutyricum, a gram-positive anaerobic bacterium, is recognized as the promising butyric acid producer. But, the existence of carbon catabolite repression (CCR) is the major drawback for C. tyrobutyricum to efficiently use the lignocellulosic biomass. In this study, the xylose pathway genes were first identified and verified. Then, the potential regulatory mechanisms of CCR in C. tyrobutyricum were proposed and the predicted engineering targets were experimental validated. Inactivation of hprK blocked the CcpA-mediated CCR and resulted in simultaneous conversion of glucose and xylose, although xylose consumption was severe lagging behind. Deletion of xylR further shortened the lag phase of xylose utilization. When hprK and xylR were inactivated together, the CCR in C. tyrobutyricum was completely eliminated. Consequently, ATCC 25755/ΔhprKΔxylR showed significant increase in butyrate productivity (1.8 times faster than the control) and excellent butyric acid fermentation performance using both mixed sugars (11.0-11.9 g/L) and undetoxified lignocellulosic hydrolysates (12.4-13.4 g/L)., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

In recent years, biomass has been reported to obtain a wide range of value-added products. Biochar can be obtained by heating biomass, which aids in carbon sinks, soil amendments, resource recovery, and water retention. Microwave technology stands out among various biomass heating technologies not only for its effectiveness in biomass pyrolysis for the production of biochar and biofuel but also for its speed, volumetrics, selectivity, and efficiency. The features of microwave-assisted biomass pyrolysis and biochar are briefly reviewed in this paper. An informative comparison has been drawn between microwave-assisted pyrolysis and conventional pyrolysis. It focuses mainly on technological and economic scenario of biochar production and environmental impacts of using biochar. This source of knowledge would aid in the exploration of new possibilities and scope for employing microwave-assisted pyrolysis technology to produce biochar., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

The alkali-halophilic Halomonas alkalicola M2 was isolated and developed for an open unsterile polyhydroxyalkanoate (PHA) fermentation from lignocellulose at pH 10.0 and NaCl 70 g/L. The alkaline pretreatment liquid (APL) was converted into PHA by the strain, which was significantly affected by the cultural conditions, including pH, NaCl concentration, nitrogen source, and APL concentration. The extracted PHA was composed of three monomers and similar in physicochemical properties to conventional short chain-length PHA. A record yield of 2.1 and 5.9 g of PHA was accumulated from 100 g dry bamboo powder (BP) by using APL and APL combined with hydrolysate during a 48-h open unsterile fermentation process, respectively. In summary, the alkali-halophilic H. alkalicola M2 achieved the open unsterile fermentation for lignocellulose efficient bioconversion into PHA under high alkalinity and salinity conditions and would be an ideal producer in the field., (Copyright © 2022. Published by Elsevier Ltd.)

The present study reports the combined enzymatic production efficiency of thermophilic fungus Thermomyces lanuginosus VAPS25 using a combinatory artificial intelligence-based tool, resulting in 2.7 IU/ml, 5.2 IU/ml, and 18.85 U/ml activity of endoglucanase, amylase, and lipase, respectively with good thermostability at 90 °C (pH 8-10). Interestingly, the metal ions viz. Cu 2+ and Mg 2+ increased the endoglucanase activity to 5 folds, i.e.,5.6 IU/ml compared to control. Further, the amylase and lipase activity was also enhanced by Fe 2+ and Co 2+ to 5.4 IU/ml and 19.57 U/ml, respectively. Additionally, the deinking efficiency was improved by 68.9%, 42.7%, and 52.8% by endoglucanase, amylase, and lipase, respectively, while the consortium increased the deinking efficiency to 72.7%. The bio-bleached paper strength parameters such as burst index, breaking length, tear index, and tensile index of sheets were significantly improved by 1.38%, 13.54%, 7.54%, and 20.88%, respectively. These enzymes at an industrial scale would help develop an economical paper recycling process., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Lignocellulose biomass is a natural porous medium with fractal characteristics, which tend to be distinct after certain pretreatment and relational with processing effects. In this work, multi-scale fractal features of corn stalks after steam explosion pretreatment were systematically characterized employing digital image processing and mercury intrusion porosimetry methodologies. The macroscopic surface fractal features (D s : 2.8278 ∼ 2.8523) and microscopic pore fractal features (D p : 2.3003 ∼ 2.8867) presented same variation tendency with pretreatment severity, revealing the self-similarity of processing results of corn stalks with the scale. In association with pretreatment homogeneity and efficacy, the decrease in fractal dimensions corresponded to morphologically homogeneous and structurally complex samples with preferable auto-hydrolysis degree of structural components, which led to high reactivity with enzymes. Quantitatively, there were strongly linear correlation between fractal dimensions and enzymatic digestibility with r 2  > 0.95. Fractal dimension was expected to theoretically guide the rational evaluation, prediction and promotion of the key pretreatment technique in biorefinery., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

The complex structure of lignocellulosic biomass forms the recalcitrance to prevent the embedded holo-cellulosic sugars from undergoing the biodegradation. Therefore, a pretreatment is often required for an efficient enzymatic lignocellulosic hydrolysis. Recently, glycerol organosolv (GO) pretreatment is revealed potent in selective deconstruction of various lignocellulosic biomass and effective improvement of enzymatic hydrolysis. Evidently, the GO pretreatment is capable to modify the structure of dissolved components by glycerolysis, i.e., by trans-glycosylation onto glyceryl glycosides and by hydroxylation grafting onto glyceryl lignin. Such modifications tend to protect these main components against excessive degradation, which can be mainly responsible for the obviously less fermentation inhibitors arising in the GO pretreatment. This pretreatment can provide opportunities for valorization of emerging lignocellulosic biorefinery with production of value-added biochemicals. Recent advances in GO pretreatment of lignocellulosic biomass followed by enzymatic hydrolysis are reviewed, and perspectives are made for addressing remaining challenges., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

In this work, effects of sulfomethylated lignins (SLs) prepared from masson pine (SL M ) and poplar (SL P ) on enzymatic hydrolysis and cellulase-lignin interaction were comparatively investigated. The results showed that both SL M and SL P significantly promoted the substrate enzymatic digestibility. The total sugar yield increased from 38.6% to 74.4% and ∼ 100%, respectively at 10 FPU/g-cellulose of cellulase dosage. The protein content in hydrolysate linearly increased with the addition of SL (0 - 1.6 g/g-substrate lignin), which suggested the competitive adsorption of cellulase may occur to substrate lignin and SLs. Further structural analysis of lignin revealed the high S/(V + H) ratio was directly related to the high enzymatic saccharification efficiency. The strong interaction between SL and cellulase decreased the nonproductive adsorption of cellulase onto substrate lignin and increased the accessibility of cellulase to carbohydrate, which was considered to be the key factor for the improvement of substrate enzymatic digestibility., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

The chemical structure of lignin has an important effect on the lignin pyrolysis product distributions. Therefore, it is of great significance to regulate the selectivity of pyrolysis products by modifying the lignin structure. Herein, deep eutectic solvents (DESs) including choline chloride/ethylene glycol (CE), zinc chloride/ethylene glycol (ZE) and choline chloride/acetic acid, treatment of softwood kraft lignin (SKL) is demonstrated. Systematic characterization indicate that the DESs are not only highly conducive to increasing the hydrogen to carbon efficient ratio, reducing the molecular weight and β-O-4 linkage, but also contributes to the maximum degradation rate and thermal stability of SKL. Noticeably, CE and ZE treatment are significantly improved the amount of H-phenols and C-phenols derived lignin pyrolysis, respectively. In addition, DESs pretreatment are also beneficial to the increment of monomer aromatic hydrocarbons. More importantly, the CE pretreatment contributes to the improvement of bio-oil yield and decrease of char content from lignin pyrolysis., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

A pretreatment method combining ball-milling, ultrasound, and hydrothermal treatment was developed to produce xylooligosaccharides (XOS) and glucose with a high yield from corn stover. Under optimal conditions, the yield of XOS reached 80.40%, and the functional XOS (X2-X4) took up to 26.97%. Small amount of inhibitors were formed during the hydrothermal process. Enzymatic hydrolysis of the hydrothermally pretreated residue gave 92.60% yield of glucose, leaving lignin as the final residue which accounted for 66.82% of native lignin. The correlations between the yield of glucose and the physio-chemical properties of corn stover, such as crystalline index, particle size, and the removal of xylan, were established to understand the recalcitrance removal during the pretreatment process. Results demonstrate that this combined pretreatment method is a green and effective process to selectively separate the hemicellulose fractions and improve both production of XOS and glucose yield., (Copyright © 2021. Published by Elsevier Ltd.)

Microbiota quorum sensing (QS) induced by 3O-C6-HSL (N-(β-ketocaproyl)-DL-homoserine lactone) inhibited the calcification of anaerobic granular sludge (AnGS), and the mechanism of promoting the activity recovery of calcified AnGS was studied in this paper. Through research, it was speculated that 3O-C6-HSL acted on calcified AnGS residual microorganisms to trigger QS. It enriched many functional microorganisms. For example, it promoted the growth of Methanospirillum. The CO 2 could be consumed quickly by Methanospirillum and reduced the calcium carbonate formation. The increase of microbial biomass would promote the activity of sludge. What's more, the pore size and porosity of sludge would increase, so the mass transfer channel will be broadened at same time. All those, could help the calcified AnGS quickly restore the activity and anaerobic system recover normal, which provided a new idea for the emergency rescue of anaerobic system in the future., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

In this work, near-complete conversion of lignocellulosic biomass and high products yields were achieved through catalytic transfer hydrogenolysis (CTH) in isopropanol using a heteropoly acid SiW 12 synergistic with Pd/C catalyst at a relatively mild condition. The performances of various heteropoly acids and catalytic conditions were extensively examined. The results confirmed that SiW 12 exhibited the highest activity on disrupting C-C linkages and C-O linkages than H 2 WO 4 , PW 12 , and PMo 12 . 34.91 wt% and 43.55 wt% monophenols were achieved for hydrogenolysis of bagasse and eucalyptus, respectively, at their optimal temperature for 5 h. Characterization studies on the lignin oil revealed that the notable structural changes were observed including the breaking of the side chain alkyl-aryl ether bonds and glycosidic bonds, while methoxyl groups were retained. Additionally, particle size of feedstock also has significant impact on the distribution and yields of the monophenols., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

The addition of various metallic chlorides in pretreatment of lignocellulose have been widely reported to improve cellulose conversion via cellulolytic processing. However, the interaction mechanism between lignin and metallic cations is not well known. In this work, pretreatment with different concentrations of FeCl 3 and AlCl 3 were performed upon waste wheat straw to enhance enzymatic hydrolysis efficiency. Results showed that pretreatment with FeCl 3 and AlCl 3 could facilitate the enzymatic hydrolysis efficiency increasing from 50.4% to 82.9% and 76.6%, which was attributed to the enhancement of xylan removal by 33.8% (FeCl 3 ) and 36.5% (AlCl 3 ), respectively. Meanwhile, the surface charge, hydrophobicity, and protein adsorption capacity of lignin from waste wheat straw can be decreased by 3.3 mV, 0.6 L/g, 7.6 mg/g (FeCl 3 ). This was due to the depolymerization of lignin in metallic chlorides pretreatment. These findings will be used to further evaluate the effect of metallic chlorides in biorefinery pretreatment., (Copyright © 2021 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.)

The aim of this work was to develop a feasible ball mill-assisted alkaline peroxide pretreatment followed by stepwise hydrolysis to improve the yield of xylo-oligosaccharides (XOS) and fermentable sugars. The hydrogen peroxide charge, ball-milling time, and solid-to-liquid ratio affected the compositions, particle sizes, morphology, and crystallinity of the corn stover, directly improving the following hydrolytic efficiency. The optimal pretreatment was with 0.45 g/g (H 2 O 2 : substrate) and 1:3 solid-to-liquid ratio (w/v) for 1.0 h ball-milling, resulting in 84.29% delignification. Physicochemical properties of the pretreated samples were characterized and their correlations to the enzymatic hydrolysis were revealed. Compared with one-step cellulase hydrolysis, the two-step xylanase-cellulase hydrolysis of the pretreated corn stover showed significant advance in preparing XOS, producing 69.65% (on the base of xylan content in pretreated sample) of XOS, along with 20.55% xylose, 68.94% glucose, and 21.15% gluco-oligosaccharides. The yield of XOS was 2-7 times higher than those in previous studies., (Copyright © 2021. Published by Elsevier Ltd.)

The sulfur(thiosulfate)-driven autotrophic denitrification coupled with Anammox (SDDA) process is proposed as an emerging technology for wastewater containing NH 4 + -N and NO 3 - -N. However, the influence of organic matter on the SDDA process is not fully understood. A long-term experiment has shown that a moderate organic (acetate) (＜140 mg/L COD) can accelerate the heterotrophic/autotrophic denitrification and Anammox activity, to reach as high as 92.8% ± 0.3% total nitrogen at a loading rate of 1.34 kg-N/(m 3 ·d). Batch test results showed that Anammox made the largest contribution to the removal of nitrogen, even in an SDDA system with COD addition. Additionally, organics can promote the bioavailability of solid sulfur through reaction with sulfide to form polysulfides, which increased nitrite accumulation to forward Anammox process. Sulfur-oxidizing bacteria (e.g., Thiobacillus and Denitratisoma) coexisted with Anammox bacteria (e.g., Ca. Brocadia and Ca. Kuenenia) in the SDDA system despite the addition of exogenous COD., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Deep eutectic solvents (DESs) have received considerable interests as pretreatment solvents for biorefinery. In the present work, five kinds of dicarboxylic acids based DESs were introduced to pretreatments on moso bamboo (MB) with microwave irradiation assistance. Factors influencing the enzymatic conversion of MB cellulose to glucose were determined. With the fast heating, pretreated samples all present significant delignification and hemicelluloses matrix removal, thus improving the enzymatic conversion yield from 15% of MB to ~60%. For the DESs, hydrogen donors with less carbon atoms (oxalic acid) and more hydroxyl groups (tartaric acid) displayed higher efficiency due to separation of aggregated cellulose microfibrils. The microwave assisted DESs (MW-DESs) pretreatments also contributed to cellulose crystal variations including decrystallization and more exposure of hydrophobic surfaces, which are beneficial for followed cellulase adsorption and hydrolysis. The exploration of fast MW-DESs pretreatments may expand the potentials of lignocellulose biomass on effective and applicable biorefinery., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

In this study, two counterexamples of lignin preoxidation-hydroconversion were reported. First, two lignin feedstocks were preoxidized with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) in acetonitrile with various dosages (15%, 30%, and 60%). Then, these preoxidized lignins (HELOs and MWLOs) were hydroconverted in supercritical ethanol catalyzed by Cu/CuMgAlO x . Total yields from HELOs were all higher than those from HEL, indicating the good promotion of DDQ preoxidation on the subsequent hydroconversion of HELOs, especially with the DDQ dosage of 15%. Differently, the promotion effect of DDQ preoxidation on the hydroconversion of MWLOs depended on the DDQ dosage as well as the reaction time. Through the comparison of two counterexamples, this work bursted the myth that preoxidation can always promote the subsequent hydroconversion of lignin, revealed the influence of lignin property, preoxidation degree, and reaction conditions on the subsequent hydroconversion of preoxidized lignin, and presented the new insight into the preoxidation-hydroconversion strategy for lignin., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

The high content of lignin in bamboo is considered as the major obstacle for its biorefining. In this work, a green, lignin-selective, and recyclable solvent of phenoxyethanol was coupled with acid solution to deconstruct recalcitrant structure of bamboo residues (BR) to boost its enzymatic digestibility. Results showed phenoxyethanol has excellent lignin-removal ability from 29.4% to 91.6% when phenoxyethanol:acid ratios increased from 0:1 to 4:1 at 120 °C. 82.5%-87.8% of cellulose was preserved in pretreated BR. The enzymatic digestibility of BR significantly improved from 20.0% to 91.3% when it was pretreated under optimized conditions. With lower enzyme dosages (10 FPU/g) and 5 recycled using of pretreatment liquor, pretreated BR still showed a good enzymatic digestibility of 67.4%-93.7% and 67.1-76.8%, respectively. Examination of physicochemical changes revealed that improvements to accessibility, reduction of crystallite size, decrease of surface lignin and hydrophobicity for pretreated BR showed positive correlations (R 2  > 0.7) with their enzymatic digestibility., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Lignin is considered as a promising substitute for fossil resources, but its efficient conversion remains a huge challenge due to the structural complexity and immiscibility with typical solvents. Herein, a series of surfactant-free microemulsion reactors comprised of n-octane, water and n-propanol were designed and their corresponding phase behaviors alongside their ability to intensify oxidative depolymerization of lignin were explored. Experimental results show that the phenolic monomer yield improves substantially (40-500 wt%) by comparison with processes performed in a single solvent. Detailed characterizations also suggest that the above intensification is rationalized by the solubilization effect of microemulsion system and directional aggregation of lignin at the microemulsion interface., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Viscosity control and reactivity enhancement are of practical importance for high-quality dissolving pulp manufacturing. In this work, we demonstrate a two-step activating process consisting of a phosphotungstic acid (PTA)-assisted prerefining (PTA/R pretreatment), followed by cellulase treatment for this purpose. The cellulase adsorption can increase from 29.1% to 49.7% as a result of PTA/R pretreatment (8000 r at 90 °C). The viscosity of the resultant pulp decreases from 665 to 430 mL/g, while its Fock reactivity increases from 31.5% to 74.4% under a low-loading cellulase treatment (0.5 mg cellulase /g odp), which mainly due to the fact that the PTA/R pretreatment can increase fiber accessibility and viscosity control, thus facilitating cellulase adsorption and reaction efficiency. Moreover, PTA also shows a high recyclability/ reusability (more than 86%) during the PTA/R pretreatment. Therefore, the new proposed two-step activating process provides a green, and efficient pathway for large-scale manufacturing of high-quality dissolving pulp., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

In this study, five acid or alkali catalyzed ethylene glycol (EG) organosolv pretreatments were proposed and compared for sugar production from bagasse. The results showed that compared with single EG/H 2 O pretreatment, the EG/H 2 O-HCl pretreatment was more efficient for both hemicellulose (~99.3%) and lignin (~67.1%) remove due to the synergistic effect of HCl and EG. The EG/H 2 O-NaOH pretreatment was also beneficial for lignin remove (~90.9%), but it was weak for hemicellulose degradation (~28.8%). Both EG/H 2 O-HCl and EG/H 2 O-NaOH pretreatments have good capacity to reserve the cellulose in pretreated solids. Following enzymatic saccharification, the largest glucose recovery yield from EG/H 2 O-HCl pretreatment was 94.3%, a slightly higher than this from EG/H 2 O-NaOH pretreatment (92.5%). However, its xylose recovery yield was only 77.3%, significantly lower than that of EG/H 2 O-NaOH pretreatment (93.5%). Besides, a certain amount of lignin also can be recovered from above acid or alkali catalyzed organosolv pretreatments through diluting or acidizing the pretreated liquids., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Alkali lignin (AL) and sodium lignosulfonate (SLS) are by-products of the papermaking industry and could influence composting processes due to their rich aromatic structures. In this study, the roles of AL and SLS additives in the formation of humic substances (HS) during paper mill sludge composting were investigated. Results showed that HS content and degree of polymerization of the final products in AL (44.42 mg·g -1 and 0.70, respectively) and SLS (45.87 mg·g -1 and 1.14, respectively) treatments were appreciably higher than those of the control sample (34.36 mg·g -1 and 0.67). Excitation-emission matrix-parallel factor coupled with two-dimensional FT-IR correlation spectroscopy analysis suggested that AL and SLS additives could speed the transformation of quinone-like substances by increasing the amounts of low molecular weight lignin depolymerized products, which led to higher HS concentrations. This work provided a way of promoting HS formation and the comprehensive utilization of papermaking wastes., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

The effect of NaOH catalytic ethanol pretreatment under various temperatures (130-180 °C) and time (15-90 min) on the chemical composition and enzymatic saccharification of sugarcane bagasse was investigated in this study. The results showed that NaOH catalytic ethanol pretreatment assisted delignification and the reservation of cellulose and hemicellulose. When sugarcane bagasse was pretreated at 180 °C for 30 min, a substantial glucose yield of 91.6% was obtained after hydrolysis for 72 h, representing 94.6% of glucose in pretreated residue. This yield was promoted with respect to the compositional change and surface alteration of pretreated substrate. With the supplement of Tween 80, the enzyme usage would be saved by 50% and the enzymolysis time could be shortened to 24 h while obtaining comparable glucose yield. This study provided an economical feasible and gradual process for the generation of glucose, which was followed by fermentation and conversion to platform chemicals., (Copyright © 2020 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.)

In this work, an emerging and efficient strategy for the preparation of lignin samples with different acetylation degree by choline chloride/acetic anhydride (ChCl/Aa) treatment of pine kraft lignin (PKL) is reported, and the effects of efficient pre-acetylation of hydroxyl functional groups on subsequent lignin pyrolysis are also systematically investigated. The results show that the ChCl/Aa displays a high acetylation efficiency towards the aliphatic hydroxyl (~99.1%) and phenolic hydroxyl (~94.0%) of PKL, which enhances the hydrogen to carbon effective ratio of PKL. Noticeably, the ChCl/Aa has a slight effect on β-O-4 of PKL, and the acetylation of hydroxyl is beneficial for the improvement of the maximum degradation rate of PKL. In addition, the acetylation of hydroxyl is also significantly contributed to the increment of the pyrolysis bio-oil yield. Importantly, the relative content of the H-phenols obtained from acetylated lignins pyrolysis shows a positive correlation with the acetylation degree of hydroxyl., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Enzymatic hydrolysis of three pre-treated lignocellulosic biomasses -LCB- (wheat straw-WS-, corn stover-CSV- and cardoon stems -CS-) is studied. These biomasses were pre-treated by two methods: diluted sulfuric acid and acid ethanol-water extraction at six severity levels (H values). Pretreated solid fractions were hydrolyzed with commercial enzyme cocktails at standard conditions. A first-order kinetic fractal model was fitted to the experimental results. This model accurately describes the hydrolysis of all biomasses at all pre-treatment conditions studied. The results show that the formal first-order kinetic constant k depends on the biomass nature. The hydrolysis rate increases as the pre-treatment severity does, while the fractal exponent value h decreases. With these pre-treatments, and in terms of k and h, WS is highly reactive and, at medium H with EW pretreatment, highly accessible; CSV has a low reactivity and high accessibility and CS has the lowest reactivity and an increasing accessibility as severity rises., (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.)

Centrifugation is very common in the production and treatment of lignocellulose for applications like pretreatment for enzymatic hydrolysis, but it is not certain whether it affects applications of lignocellulose and almost no one realizes this problem. This study investigated the effects of centrifugation on the characteristics and enzymatic hydrolysis of poplar fibers with high lignin content. The results showed that centrifugation inhibited the enzymatic hydrolysis of fiber, but fiber characteristics and enzymatic digestibility fluctuated with increasing centrifugation time. Centrifugation for about 15 min had the least effect on fiber properties while centrifugation for 30 min had the least effect on enzymatic hydrolysis. The water retention value was closely related to the enzymatic digestibility, but the pore characteristics and crystallinity index could not reflect the enzymatic accessibility of the fiber. This article will provide useful references for the enzymatic hydrolysis of lignocellulose and other high-value applications to improve production efficiency furtherly., 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.)