Effect of hydrothermal pretreatment on the structural changes of alkaline ethanol lignin from wheat straw

Chen, Xue; Li, Hanyin; Sun, Shao‐Ni; Cao, Xuefei; Sun, Run‐Cang

doi:10.1038/srep39354

Cited by 96 publications

(50 citation statements)

References 39 publications

(44 reference statements)

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“…Thus, as expected, the structure of lignin is affected by temperature, which is a finding previously reported (see e.g. Chen et al 24 ). In this sense, 150 ∘ C and ethyl lactate-enriched solutions could be preferred as organosolv operating conditions for those interested in the exploitation of remnant sugars in the solid waste instead of lignin recovery.…”

Section: Resultssupporting

confidence: 89%

Optimization of ethyl lactate‐based organosolv process for lignin recovery from the solid waste of a wheat straw biorefinery

Valdespino‐Rodríguez

Pérez-Martín

González‐Barajas

et al. 2019

J of Chemical Tech & Biotech

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BACKGROUND: The organosolv process promotes biomass delignification at relatively high temperatures using a wide variety of organic solvent solutions. Nevertheless, previous studies on organosolv processes have not dealt with the use of ethyl lactate as organic solvent. Thus the aim of the present contribution was to determine and to validate if the use of ethyl lactate has a positive influence on lignin recovery for organosolv processes whose feedstock is the solid waste from a wheat straw-based biorefinery. The effect of operating conditions (temperature and time) on lignin recovery was also studied. RESULTS: A mixed design of experiments was proposed as the strategy to maximize lignin recovery. The mathematical model derived from a multiple linear regression applied to the mixed design results indicates that 190 ∘ C and a non-aqueous solution containing ethyl lactate and ethanol (81.2% w/w ethyl lactate) could provide a maximum lignin recovery of 75.9% w/w. This theoretical maximum was validated. Thus the proposed model adequately describes the behavior of lignin recovery. Moreover, Fourier transform infrared (FTIR) characterization of the resultant lignin suggested that its structure is a function of the organic solvent solution used during the organosolv process.CONCLUSION: The evidence from this study indicates that lignin recovery from the solid waste of a wheat straw-based biorefinery in an organosolv process depends on temperature and ethyl lactate presence in the reaction medium. These findings enhance the understanding of organosolv processes and could be applied if eventual lignin valorization is desired.Corrections added on 24 January 2020, after first online publication: the second occurrence of the term "m residue " in Equation 1 has been changed to "m sample ". Also the term "m sample " has been included in the sentence "In summary, 300.0 ± 10.0 mg of the solid waste was weighed in a pressure tube" under the section "Washings and lignin content quantification in solid waste".

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Section: Resultssupporting

confidence: 89%

Optimization of ethyl lactate‐based organosolv process for lignin recovery from the solid waste of a wheat straw biorefinery

Valdespino‐Rodríguez

Pérez-Martín

González‐Barajas

et al. 2019

J of Chemical Tech & Biotech

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“…The relatively high intensity of the 1320 cm −1 peak compared with the 1270 cm −1 peak, as well as the strong intensity of the band at 1123 cm −1 , which is also typical for syringyl units and is attributed to aromatic C−H in‐plane bending, are in accordance with the expected high ratio of syringyl over guaiacyl units in hardwood native lignins . Furthermore, the intensity of these bands is similar amongst the lignins isolated from the 190 and 220 °C treated biomass samples, although partial demethoxylation of alkaline ethanol lignin from wheat straw at severe hydrothermal conditions has been previously reported …”

Section: Resultssupporting

confidence: 75%

“…This indicates that severe hydrothermal pretreatment conditions favor the formation of carbonyl groups in the isolated lignin. This has been attributed to the cleavage of β‐O‐4′ linkages of the native lignins and the formation of Hibbert ketones under severe pretreatment conditions . The bands at 1607, 1510, 1460, and 1427 cm −1 are assigned to the skeletal vibrations of the aromatic ring.…”

Section: Resultsmentioning

confidence: 99%

Enhancing Lignocellulosic Biomass Hydrolysis by Hydrothermal Pretreatment, Extraction of Surface Lignin, Wet Milling and Production of Cellulolytic Enzymes

et al. 2019

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Acetone and ethanol extraction of lignin deposits from the surface of hydrothermally (liquid hot water) pretreated beech wood biomass alleviates the lignin inhibitory effects during enzymatic hydrolysis of cellulose to glucose and boosts the enzymatic digestibility to high values (≈70 %). Characterization of the extracted lignins (FTIR, pyrolysis/GC–MS, differential thermogravimetry, gel permeation chromatography) indicated high purity, low molecular weight, and features that suggest that it consists mainly of fragments of the native wood lignin partially depolymerized and recondensed on the biomass surface during the hydrothermal pretreatment. The pyrolysis products of the extracted surface lignins suggest their high potential as a feedstock for the production of high added value phenolic compounds. When the enzymatic hydrolysis of the pretreated and extracted biomass solids was assisted by mild wet milling, near complete cellulose digestibility (≥95 %) could be achieved. In the context of the biorefinery and whole‐biomass valorization concept, it was also shown that the hydrothermally (hemicellulose‐deficient) pretreated and delignified biomass solids could be also successfully used for the production of crude cellulase from Trichoderma reesei cultures, providing a simple and low‐cost method for the complementary production of cellulases by utilizing fractions of the integrated hydrolysis process.

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“…Sun et al. combined hydrothermal pretreatment and alkaline ethanol extraction to remove lignin from wheat straw, and observed that β−O−4, β−β′, and β−5 linkages, as well as aliphatic OH in lignin, showed a tendency of being broken, but phenolic OH increased steadily with increasing temperature . It was noted that some hydrogen bonds and ether linkages between lignin and cellulose/or hemicellulose, as well as those in lignin, were broken during the process.…”

Section: Introductionmentioning

confidence: 99%

Performances of Several Solvents on the Cleavage of Inter‐ and Intramolecular Linkages of Lignin in Corncob Residue

Zhang

et al. 2018

ChemSusChem

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The performances of solvents, including γ-butyrolactone (GBL), γ-valerolactone (GVL), tetrahydrofuran (THF), ethyl acetate (EAC), 2-methyltetrahydrofuran (2-MeTHF), and the corresponding mixtures with H O, on the cleavage of inter- and intramolecular linkages of lignin in corncob residue were investigated. At 200 °C, miscible cosolvents (H O-GBL, H O-GVL, and H O-THF) exhibited much better efficiency for lignin dissolution than that of both immiscible cosolvents (H O-EAC and H O-2-MeTHF) and pure solvents. The synergetic effect between H O and organic solvent significantly promoted the breakage of intermolecular linkages between C6-O-H of amorphous cellulose and lignin. GBL and THF solvents preferentially dissolved lignin with H and G units, whereas GVL, EAC, and 2-MeTHF solvents exhibited high selectivity for the dissolution of lignin with S and G units. In addition to dissolution, the intramolecular β-O-4 linkage in lignin could be selectively cleaved in H O-GBL cosolvent, whereas the β-O-4, α-O-4, and β-5 linkages were cleaved in H O-EAC, H O-THF, and H O-2-MeTHF cosolvents. At 300 °C, the breakage of the β-γ bond prior to β-O-4 in H O-GBL, H O-THF, H O-EAC, and H O-2-MeTHF produced 4-ethylphenol and 4-ethylguaiacol selectively (accounting for ≈70 % of the total identified monophenols), whereas the α-1 bond was preferably broken in H O-GVL to form guaiacol (accounting for ≈75 % of the total identified monophenols).

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Effect of hydrothermal pretreatment on the structural changes of alkaline ethanol lignin from wheat straw

Cited by 96 publications

References 39 publications

Optimization of ethyl lactate‐based organosolv process for lignin recovery from the solid waste of a wheat straw biorefinery

Optimization of ethyl lactate‐based organosolv process for lignin recovery from the solid waste of a wheat straw biorefinery

Enhancing Lignocellulosic Biomass Hydrolysis by Hydrothermal Pretreatment, Extraction of Surface Lignin, Wet Milling and Production of Cellulolytic Enzymes

Performances of Several Solvents on the Cleavage of Inter‐ and Intramolecular Linkages of Lignin in Corncob Residue

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