Lignin repolymerisation in spruce autohydrolysis pretreatment increases cellulase deactivation

Pielhop, Thomas; Larrazábal, Gastón O.; Studer, Michael Hans-Peter; Brethauer, Simone; Seidel, Christoph-M.; Rohr, Philipp Rudolf von

doi:10.1039/c4gc02381a

Cited by 160 publications

(144 citation statements)

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“…Such a mechanism is able to explain lignin solubilization in hot water conditions that cannot be attributed to acid catalyzed cleavage of β- O -4 linkages in lignin due to an autohydrolysis reaction [21, 22]. As in LHW flowthrough pretreatment at relatively short residence times, acetic acid liberated from acetylated xylans is removed from the reactor before it can cause a drop in solution pH.…”

Section: Resultsmentioning

confidence: 99%

“…On the other hand, flowthrough pretreatment removes these lignin-oligomer fragments before they have time to breakdown to lower solubility products [19]. Other than a lignin-hemicellulose fragmentation mechanism, some studies indicated that lignin depolymerization at acidic conditions can proceed through formation of carbenium intermediates followed by cleavage of β- O -4 linkages in lignin [20–22]. As a result of enhanced lignin removal by flowthrough pretreatment, digestion of the glucan left in flowthrough solids by enzymes can achieve near theoretical glucan yields [23].…”

Section: Introductionmentioning

confidence: 99%

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Flowthrough pretreatment with very dilute acid provides insights into high lignin contribution to biomass recalcitrance

Bhagia

Gao

et al. 2016

Biotechnol Biofuels

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BackgroundFlowthrough pretreatment is capable of removing much higher quantities of hemicellulose and lignin from lignocellulosic biomass than batch pretreatment performed at otherwise similar conditions. Comparison of these two pretreatment configurations for sugar yields and lignin removal can provide insights into lignocellulosic biomass deconstruction. Therefore, we applied liquid hot water (LHW) and extremely dilute acid (EDA, 0.05%) flowthrough and batch pretreatments of poplar at two temperatures and the same pretreatment severity for the solids. Composition of solids, sugar mass distribution with pretreatment, sugar yields, and lignin removal from pretreatment and enzymatic hydrolysis were measured.ResultsFlowthrough aqueous pretreatment of poplar showed between 63 and 69% lignin removal at both 140 and 180 °C, while batch pretreatments showed about 20 to 33% lignin removal at similar conditions. Extremely dilute acid slightly enhanced lignin removal from solids with flowthrough pretreatment at both pretreatment temperatures. However, extremely dilute acid batch pretreatment did realize greater than 70% xylan yields largely in the form of monomeric xylose. Close to 100% total sugar yields were measured from LHW and EDA flowthrough pretreatments and one batch EDA pretreatment at 180 °C. The high lignin removal by flowthrough pretreatment enhanced cellulose digestibility compared to batch pretreatment, consistent with lignin being a key contributor to biomass recalcitrance. Furthermore, solids from 180 °C flowthrough pretreatment were much more digestible than solids pretreated at 140 °C despite similar lignin and extensive hemicellulose removal.ConclusionsResults with flowthrough pretreatment show that about 65–70% of the lignin is solubilized and removed before it can react further to form low solubility lignin rich fragments that deposit on the biomass surface in batch operations and hinder enzyme action. The leftover 30–35% lignin in poplar was a key player in biomass recalcitrance to enzymatic deconstruction and it might be more difficult to dislodge from biomass with lower temperature of pretreatment. These results also point to the possibility that hemicellulose removal is more important as an indicator of lignin disruption than in playing a direct role in reducing biomass recalcitrance.Electronic supplementary materialThe online version of this article (doi:10.1186/s13068-016-0660-5) contains supplementary material, which is available to authorized users.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Flowthrough pretreatment with very dilute acid provides insights into high lignin contribution to biomass recalcitrance

Bhagia

Gao

et al. 2016

Biotechnol Biofuels

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“…This indicated that products resulting from the partial degradation of lignin and lignin fragments were removed by the neutral and acidic detergents with hemicelluloses. A slight increase in ADL content was observed after the fourth pretreatment cycle, indicating a gradually increasing degree of repolymerization of lignin (Pielhop et al 2015). The decrease in SHS content was consistent with the degradation of cellulose, and subsequent removal of degradation products by the acidic detergent.…”

Section: Changes In the Chemical Components Of Ebmentioning

confidence: 55%

Changes in the Microstructure and Components of Eulaliopsis binata Treated by Continuous Screw Extrusion Steam Explosion

Feng¹,

Lei²,

Liang³

et al. 2016

BioResources

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Eulaliopsis binata (EB) was pretreated by continuous screw extrusion steam explosion (SESE), with the aim of converting EB into useful materials on an industrial scale. The three main chemical components were characterized by component analysis using the Van Soest fiber detergent system, ultraviolet (UV) absorption spectrophotometry, gel permeation chromatography (GPC), and carbon-13 nuclear magnetic resonance ( 13 C-NMR) spectroscopy. Changes in the contents of detergent soluble species in the Van Soest process revealed the partial degradation of hemicellulose and cellulose, and the partial removal of lignin. GPC indicated that the molecular weight of lignin decreased from 4194 to 3710 g/mol over the first three SESE pretreatment cycles, but then increased to 4592 g/mol following the fourth SESE pretreatment cycle. UV absorption and 13 C-NMR results indicated the partial removal of lignin and the depolymerization and repolymerization of lignin during SESE pretreatment. Scanning electron microscopy (SEM) showed that the epidermis and parenchyma of EB were almost completely desquamated. X-ray diffraction (XRD) revealed that the crystallinity of EB initially increased and then subsequently decreased slightly, with increasing number of SESE pretreatment cycles. The varying physicochemical properties of EB resulting from different numbers of pretreatment cycles may find use in more diverse applications.

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“…Softwoods are characterized by being more recalcitrant to enzymatic hydrolysis than hardwoods or agricultural residues owing to their type and content of lignin . In addition, the major hemicelluloses in softwoods are galactoglucomannans (GGMs), whereas xylans are the dominant hemicelluloses in other lignocellulosic materials . Pinus radiata is a versatile, fast‐growing, medium‐density softwood, which can be employed for a wide range of end uses.…”

Section: Introductionmentioning

confidence: 99%

Two‐step fractionation of Pinus radiata by autohydrolysis and organosolv delignification for enzymatic hydrolysis

Santos

Rigual

Oliet

et al. 2019

J of Chemical Tech & Biotech

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BACKGROUND Lignocellulosic biomass is a promising renewable feedstock to obtain fuels and chemicals. However, a suitable pretreatment is required to separate its main components and overcome its structural resistance to enzymatic hydrolysis. In this work, a sequential pretreatment composed of autohydrolysis (AH) and organosolv delignification (ORG) is used to fractionate Pinus radiata wood and improve the enzymatic hydrolysis. RESULTS The effect of three different AH pretreatment severities on the delignification degree of organosolv solid fractions was evaluated. In addition, enzymatic hydrolysis was performed to determine the efficiency of the combination of pretreatments. The results showed that a pretreated solid with high cellulose content (88%, w/w) and high delignification degree (88%) was achieved under mild conditions of AH (150 °C and 30 min) and acid‐catalyzed ORG (185 °C, 75 min, 50% (w/w) ethanol and 1% (w/w) sulfuric acid), obtaining an enzymatic hydrolysis yield of 63%. CONCLUSION This study provides the most favorable conditions to fractionate a softwood, P. radiata, employing a two‐step pretreatment based on AH followed by ORG. © 2019 Society of Chemical Industry

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Lignin repolymerisation in spruce autohydrolysis pretreatment increases cellulase deactivation

Abstract: An autohydrolysis pretreatment that suppresses lignin repolymerisation helps overcoming the recalcitrance of softwood for enzymatic hydrolysis of its cellulose.

Cited by 160 publications

References 46 publications

Flowthrough pretreatment with very dilute acid provides insights into high lignin contribution to biomass recalcitrance

Flowthrough pretreatment with very dilute acid provides insights into high lignin contribution to biomass recalcitrance

Changes in the Microstructure and Components of Eulaliopsis binata Treated by Continuous Screw Extrusion Steam Explosion

Two‐step fractionation of Pinus radiata by autohydrolysis and organosolv delignification for enzymatic hydrolysis

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