The Experts below are selected from a list of 2709 Experts worldwide ranked by ideXlab platform
Arthur J Ragauskas - One of the best experts on this subject based on the ideXlab platform.
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the effect of lignin degradation products on the generation of pseudo lignin during Dilute Acid Pretreatment
Industrial Crops and Products, 2020Co-Authors: Caoxing Huang, Arthur J Ragauskas, Chenhuan Lai, Chen Huang, Qiang YongAbstract:Abstract Pseudo-lignin is an insoluble material that tends to deposit on Acidic pretreated fiber surface and negatively impacts the biological conversion of biomass to valued added products. Employing a laboratory generated Acidic hydrolysate solution from Dilute Acid Pretreatment of bamboo residues, we sought to seek an improved understanding of pseudo-lignin formation from fragmented carbohydrates. In addition, we also performed experiments to investigate how lignin model compounds interact with carbohydrates en route to pseudo-lignin’s formation. The yields of pseudo-lignin generated from xylose (CXPL) were higher than those generated from glucose (CGPL). Gas chromatography-Mass spectrometry and Foloin-Ciocalteau analysis suggested that there were more aromatic compounds in hydrolyzate during CGPL’s formation. The presence of lignin phenolic model compounds had both a positive and negative effect upon quantitative yields of pseudo-lignin. Gel permeation chromatography and NMR analysis (31P and 2D-HSQC NMR) of the pseudo-lignin samples generated in the presence and absence of 4-hydroxybenzoic Acid (4-HA), employed as a lignin model compound, revealed drastic differences in molecular weight, changes in hydroxyl group content, and hydrocarbon bonds, suggesting significant differences in the pseudo-lignin reaction pathways when certain lignin model compounds are present. Our findings demonstrate the effects of both hemicellulose carbohydrate makeup and lignin model compound impact on the formation of pseudo-lignin and its chemical properties, suggesting a potential way to minimize pseudo-lignin formation.
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hemicellulose cellulose composites reveal differences in cellulose organization after Dilute Acid Pretreatment
Biomacromolecules, 2019Co-Authors: Riddhi Shah, Arthur J Ragauskas, Daisuke Sawada, Sai Venkatesh Pingali, Shixin Huang, Miguel Rodriguez, Seong H Kim, Barbara R Evans, Brian H Davison, Hugh OneillAbstract:Model hemicellulose–cellulose composites that mimic plant cell wall polymer interactions were prepared by synthesizing deuterated bacterial cellulose in the presence of glucomannan or xyloglucan. D...
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understanding multiscale structural changes during Dilute Acid Pretreatment of switchgrass and poplar
ACS Sustainable Chemistry & Engineering, 2017Co-Authors: Sai Venkatesh Pingali, Charles E. Wyman, Marcus Foston, Hugh Oneill, Paul Langan, Volker S Urban, William T Heller, Joseph Mcgaughey, Dean A A Myles, Arthur J RagauskasAbstract:Biofuels produced from lignocellulosic biomass hold great promise as a renewable alternative energy and fuel source. To realize a cost and energy efficient approach, a fundamental understanding of the deconstruction process is critically necessary to reduce biomass recalcitrance. Herein, the structural and morphological changes over multiple scales (5–6000 A) in herbaceous (switchgrass) and woody (hybrid poplar) biomass during Dilute sulfuric Acid Pretreatment were explored using neutron scattering and X-ray diffraction. Switchgrass undergoes a larger increase (20–84 A) in the average diameter of the crystalline core of the elementary cellulose fibril than hybrid poplar (19–50 A). Switchgrass initially forms lignin aggregates with an average size of 90 A that coalesce to 200 A, which is double that observed for hybrid poplar, 55–130 A. Switchgrass shows a smooth-to-rough transition in the cell wall surface morphology unlike the diffuse-to-smooth transition of hybrid poplar. Yet, switchgrass and hybrid pop...
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effect of lignin content on changes occurring in poplar cellulose ultrastructure during Dilute Acid Pretreatment
Biotechnology for Biofuels, 2014Co-Authors: Qining Sun, Charles E. Wyman, Marcus Foston, Xianzhi Meng, Daisuke Sawada, Sai Venkatesh Pingali, Hugh Oneill, Paul Langan, Arthur J RagauskasAbstract:Background: Obtaining a better understanding of the complex mechanisms occurring during lignocellulosic deconstruction is critical to the continued growth of renewable biofuel production. A key step in bioethanol production is thermochemical Pretreatment to reduce plant cell wall recalcitrance for downstream processes. Previous studies of Dilute Acid Pretreatment (DAP) have shown significant changes in cellulose ultrastructure that occur during Pretreatment, but there is still a substantial knowledge gap with respect to the influence of lignin on these cellulose ultrastructural changes. This study was designed to assess how the presence of lignin influences DAP-induced changes in cellulose ultrastructure, which might ultimately have large implications with respect to enzymatic deconstruction efforts. Results: Native, untreated hybrid poplar (Populus trichocarpa x Populus deltoids) samples and a partially delignified poplar sample (facilitated by Acidic sodium chlorite pulping) were separately pretreated with Dilute sulfuric Acid (0.10 M) at 160°C for 15 minutes and 35 minutes, respectively . Following extensive characterization, the partially delignified biomass displayed more significant changes in cellulose ultrastructure following DAP than the native untreated biomass. With respect to the native untreated poplar, delignified poplar after DAP (in which approximately 40% lignin removal occurred) experienced: increased cellulose accessibility indicated by increased Simons’ stain (orange dye) adsorption from 21.8 to 72.5 mg/g, decreased cellulose weight-average degree of polymerization (DPw) from 3087 to 294 units, and increased cellulose crystallite size from 2.9 to 4.2 nm. These changes following DAP ultimately increased enzymatic sugar yield from 10 to 80%. Conclusions: Overall, the results indicate a strong influence of lignin content on cellulose ultrastructural changes occurring during DAP. With the reduction of lignin content during DAP, the enlargement of cellulose microfibril dimensions and crystallite size becomes more apparent. Further, this enlargement of cellulose microfibril dimensions is attributed to specific processes, including the co-crystallization of crystalline cellulose driven by irreversible inter-chain hydrogen bonding (similar to hornification) and/or cellulose annealing that converts amorphous cellulose to paracrystalline and crystalline cellulose. Essentially, lignin acts as a barrier to prevent cellulose crystallinity increase and cellulose fibril coalescence during DAP.
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suppression of pseudo lignin formation under Dilute Acid Pretreatment conditions
RSC Advances, 2014Co-Authors: Arthur J RagauskasAbstract:Pseudo-lignin is formed during Dilute Acid Pretreatment (DAP), particularly under high-severity conditions, and has been shown to significantly inhibit enzymatic hydrolysis of cellulose. To suppress its formation, DAP was modified by performing it under O2 or N2; adding surfactant (Tween-80) to the reaction mixture; or using a water–dimethyl sulfoxide (DMSO) mixture as reaction medium. Pseudo-lignin analysis showed that only the addition of DMSO to DAP reaction medium can effectively suppress pseudo-lignin formation. This was attributed to DMSO preferentially solvating and stabilizing 5-hydroxymethyl furfural (HMF) which is the key intermediate to form pseudo-lignin, thereby reducing the overall yield of pseudo-lignin. Furthermore, the addition of DMSO was shown not to reduce pseudo-lignin molecular weight or change any of its structural features significantly. Therefore, pseudo-lignin generated from aqueous DMSO DAP had similar inhibition properties as compared to that acquired from routine DAP at equal mass dosages. This study is the first demonstration that the amount of pseudo-lignin formed during DAP can be reduced, which contributes to further optimization of DAP technology.
Charles E. Wyman - One of the best experts on this subject based on the ideXlab platform.
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understanding multiscale structural changes during Dilute Acid Pretreatment of switchgrass and poplar
ACS Sustainable Chemistry & Engineering, 2017Co-Authors: Sai Venkatesh Pingali, Charles E. Wyman, Marcus Foston, Hugh Oneill, Paul Langan, Volker S Urban, William T Heller, Joseph Mcgaughey, Dean A A Myles, Arthur J RagauskasAbstract:Biofuels produced from lignocellulosic biomass hold great promise as a renewable alternative energy and fuel source. To realize a cost and energy efficient approach, a fundamental understanding of the deconstruction process is critically necessary to reduce biomass recalcitrance. Herein, the structural and morphological changes over multiple scales (5–6000 A) in herbaceous (switchgrass) and woody (hybrid poplar) biomass during Dilute sulfuric Acid Pretreatment were explored using neutron scattering and X-ray diffraction. Switchgrass undergoes a larger increase (20–84 A) in the average diameter of the crystalline core of the elementary cellulose fibril than hybrid poplar (19–50 A). Switchgrass initially forms lignin aggregates with an average size of 90 A that coalesce to 200 A, which is double that observed for hybrid poplar, 55–130 A. Switchgrass shows a smooth-to-rough transition in the cell wall surface morphology unlike the diffuse-to-smooth transition of hybrid poplar. Yet, switchgrass and hybrid pop...
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effect of lignin content on changes occurring in poplar cellulose ultrastructure during Dilute Acid Pretreatment
Biotechnology for Biofuels, 2014Co-Authors: Qining Sun, Charles E. Wyman, Marcus Foston, Xianzhi Meng, Daisuke Sawada, Sai Venkatesh Pingali, Hugh Oneill, Paul Langan, Arthur J RagauskasAbstract:Background: Obtaining a better understanding of the complex mechanisms occurring during lignocellulosic deconstruction is critical to the continued growth of renewable biofuel production. A key step in bioethanol production is thermochemical Pretreatment to reduce plant cell wall recalcitrance for downstream processes. Previous studies of Dilute Acid Pretreatment (DAP) have shown significant changes in cellulose ultrastructure that occur during Pretreatment, but there is still a substantial knowledge gap with respect to the influence of lignin on these cellulose ultrastructural changes. This study was designed to assess how the presence of lignin influences DAP-induced changes in cellulose ultrastructure, which might ultimately have large implications with respect to enzymatic deconstruction efforts. Results: Native, untreated hybrid poplar (Populus trichocarpa x Populus deltoids) samples and a partially delignified poplar sample (facilitated by Acidic sodium chlorite pulping) were separately pretreated with Dilute sulfuric Acid (0.10 M) at 160°C for 15 minutes and 35 minutes, respectively . Following extensive characterization, the partially delignified biomass displayed more significant changes in cellulose ultrastructure following DAP than the native untreated biomass. With respect to the native untreated poplar, delignified poplar after DAP (in which approximately 40% lignin removal occurred) experienced: increased cellulose accessibility indicated by increased Simons’ stain (orange dye) adsorption from 21.8 to 72.5 mg/g, decreased cellulose weight-average degree of polymerization (DPw) from 3087 to 294 units, and increased cellulose crystallite size from 2.9 to 4.2 nm. These changes following DAP ultimately increased enzymatic sugar yield from 10 to 80%. Conclusions: Overall, the results indicate a strong influence of lignin content on cellulose ultrastructural changes occurring during DAP. With the reduction of lignin content during DAP, the enlargement of cellulose microfibril dimensions and crystallite size becomes more apparent. Further, this enlargement of cellulose microfibril dimensions is attributed to specific processes, including the co-crystallization of crystalline cellulose driven by irreversible inter-chain hydrogen bonding (similar to hornification) and/or cellulose annealing that converts amorphous cellulose to paracrystalline and crystalline cellulose. Essentially, lignin acts as a barrier to prevent cellulose crystallinity increase and cellulose fibril coalescence during DAP.
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carbohydrate derived pseudo lignin can retard cellulose biological conversion
Biotechnology and Bioengineering, 2013Co-Authors: Arthur J Ragauskas, Rajeev Kumar, Charles E. Wyman, Poulomi Sannigrahi, Seokwon JungAbstract:Dilute Acid as well as water only (hydrothermal) Pretreatments often lead to a significant hemicellulose loss to soluble furans and insoluble degradation products, collectively termed as chars and/or pseudo-lignin. In order to understand the factors contributing to reducing sugar yields from pretreated biomass and the possible influence of hemicellulose derived pseudo-lignin on cellulose conversion at the moderate to low enzyme loadings necessary for favorable economics, Dilute Acid Pretreatment of Avicel cellulose alone and mixed with beechwood xylan or xylose was performed at various severities. Following Pretreatment, the solids were enzymatically hydrolyzed and characterized for chemical composition and physical properties by NMR, FT-IR, and SEM imaging. It was found that hemicelluloses (xylan) derived-pseudo-lignin was formed at even moderate severities and that these insoluble degradation products can significantly retard cellulose hydrolysis. Furthermore, although low severity (CSF ~ 1.94) Dilute Acid Pretreatment of a xylan-Avicel mixture hydrolyzed most of the xylan (98%) and produced negligible amounts of pseudo-lignin, enzymatic conversion of cellulose dropped significantly (>25%) compared to cellulose pretreated alone at the same conditions. The drop in cellulose conversion was higher than realized for cellulase inhibition by xylooligomers reported previously. Plausible mechanisms are discussed to explain the observed reductions in cellulose conversions.
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chemical transformations of populus trichocarpa during Dilute Acid Pretreatment
RSC Advances, 2012Co-Authors: Arthur J Ragauskas, Charles E. Wyman, Shilin Cao, Michael H StuderAbstract:In this study, Populus trichocarpa was subjected to Dilute Acid Pretreatment at varying Pretreatment times. The three major components of lignocellulosic biomass, namely cellulose, hemicellulose and lignin, were isolated from the starting and Dilute Acid pretreated poplar. Gel permeation chromatography (GPC) and nuclear magnetic resonance (NMR) techniques were utilized to elucidate structural transformations of poplar during Dilute Acid Pretreatment. The results demonstrated that the Pretreatment dissolved hemicelluloses and disrupted structural features of lignin and polysaccharides. As revealed by NMR, the aryl-O-ether linkage (β-O-4) of lignin was extensively cleaved and lignin repolymerization occurred during Pretreatment. The lignin was also observed to have a decrease in S/G ratio and methoxyl group content and these changes were accompanied with an increase in condensed lignin. The Dilute Acid Pretreatment resulted in a reduction in molecular weight of cellulose and hemicellulose, while no prominent change of molecular weight was observed for lignin. The polydispersity index of cellulose appeared to increase initially within a short time of Pretreatment (0.3–1 min) and start to decrease with longer Pretreatment time during the bulk phase of chain scission (5.4–26.8 min). The DA Pretreatment demonstrated no significant impact on the crystalline index (CrI) of cellulose particularly within the short time range of Pretreatments examined in this study, with CrI remaining almost unchanged during the Pretreatment time of 0.3–5.4 min and a slight increase observed as the Pretreatment time extended to 8.5 and 26.8 min.
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Carbohydrate derived-pseudo-lignin can retard cellulose biological conversion.
Biotechnology and Bioengineering, 2012Co-Authors: Rajeev Kumar, Arthur J Ragauskas, Poulomi Sannigrahi, Seokwon Jung, Charles E. WymanAbstract:Dilute Acid as well as water only (hydrothermal) Pretreatments often lead to a significant hemicellulose loss to soluble furans and insoluble degradation products, collectively termed as chars and/or pseudo-lignin. In order to understand the factors contributing to reducing sugar yields from pretreated biomass and the possible influence of hemicellulose derived pseudo-lignin on cellulose conversion at the moderate to low enzyme loadings necessary for favorable economics, Dilute Acid Pretreatment of Avicel cellulose alone and mixed with beechwood xylan or xylose was performed at various severities. Following Pretreatment, the solids were enzymatically hydrolyzed and characterized for chemical composition and physical properties by NMR, FT-IR, and SEM imaging. It was found that hemicelluloses (xylan) derived-pseudo-lignin was formed at even moderate severities and that these insoluble degradation products can significantly retard cellulose hydrolysis. Furthermore, although low severity (CSF ∼ 1.94) Dilute Acid Pretreatment of a xylan–Avicel mixture hydrolyzed most of the xylan (98%) and produced negligible amounts of pseudo-lignin, enzymatic conversion of cellulose dropped significantly (>25%) compared to cellulose pretreated alone at the same conditions. The drop in cellulose conversion was higher than realized for cellulase inhibition by xylooligomers reported previously. Plausible mechanisms are discussed to explain the observed reductions in cellulose conversions. Biotechnol. Bioeng. 2013; 110: 737–753. © 2012 Wiley Periodicals, Inc.
Melvin P. Tucker - One of the best experts on this subject based on the ideXlab platform.
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effect of mechanical disruption on the effectiveness of three reactors used for Dilute Acid Pretreatment of corn stover part 2 morphological and structural substrate analysis
Biotechnology for Biofuels, 2014Co-Authors: Peter N Ciesielski, Todd B Vinzant, Weiwei Wang, David K Johnson, Michael E Himmel, Melvin P. Tucker, Xiaowen Chen, Stephen R Decker, Bryon S DonohoeAbstract:Lignocellulosic biomass is a renewable, naturally mass-produced form of stored solar energy. Thermochemical Pretreatment processes have been developed to address the challenge of biomass recalcitrance, however the optimization, cost reduction, and scalability of these processes remain as obstacles to the adoption of biofuel production processes at the industrial scale. In this study, we demonstrate that the type of reactor in which Pretreatment is carried out can profoundly alter the micro- and nanostructure of the pretreated materials and dramatically affect the subsequent efficiency, and thus cost, of enzymatic conversion of cellulose. Multi-scale microscopy and quantitative image analysis was used to investigate the impact of different biomass Pretreatment reactor configurations on plant cell wall structure. We identify correlations between enzymatic digestibility and geometric descriptors derived from the image data. Corn stover feedstock was pretreated under the same nominal conditions for Dilute Acid Pretreatment (2.0 wt% H2SO4, 160°C, 5 min) using three representative types of reactors: ZipperClave® (ZC), steam gun (SG), and horizontal screw (HS) reactors. After 96 h of enzymatic digestion, biomass treated in the SG and HS reactors achieved much higher cellulose conversions, 88% and 95%, respectively, compared to the conversion obtained using the ZC reactor (68%). Imaging at the micro- and nanoscales revealed that the superior performance of the SG and HS reactors could be explained by reduced particle size, cellular dislocation, increased surface roughness, delamination, and nanofibrillation generated within the biomass particles during Pretreatment. Increased cellular dislocation, surface roughness, delamination, and nanofibrillation revealed by direct observation of the micro- and nanoscale change in accessibility explains the superior performance of reactors that augment Pretreatment with physical energy.
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characterization of pilot scale Dilute Acid Pretreatment performance using deacetylated corn stover
Biotechnology for Biofuels, 2014Co-Authors: Joseph Shekiro, Melvin P. Tucker, Rick Elander, Erik M Kuhn, Nicholas J Nagle, Daniel J SchellAbstract:Dilute Acid Pretreatment is a promising process technology for the deconstruction of low-lignin lignocellulosic biomass, capable of producing high yields of hemicellulosic sugars and enhancing enzymatic yields of glucose as part of a biomass-to-biofuels process. However, while it has been extensively studied, most work has historically been conducted at relatively high Acid concentrations of 1 - 4% (weight/weight). Reducing the effective Acid loading in Pretreatment has the potential to reduce chemical costs both for Pretreatment and subsequent neutralization. Additionally, if Acid loadings are sufficiently low, capital requirements associated with reactor construction may be significantly reduced due to the relaxation of requirements for exotic alloys. Despite these benefits, past efforts have had difficulty obtaining high process yields at low Acid loadings without supplementation of additional unit operations, such as mechanical refining. Recently, we optimized the Dilute Acid Pretreatment of deacetylated corn stover at low Acid loadings in a 1-ton per day horizontal Pretreatment reactor. This effort included more than 25 pilot-scale Pretreatment experiments executed at reactor temperatures ranging from 150 – 170°C, residence times of 10 – 20 minutes and hydrolyzer sulfuric Acid concentrations between 0.15 – 0.30% (weight/weight). In addition to characterizing the process yields achieved across the reaction space, the optimization identified a Pretreatment reaction condition that achieved total xylose yields from Pretreatment of 73.5% ± 1.5% with greater than 97% xylan component balance closure across a series of five runs at the same condition. Feedstock reactivity at this reaction condition after bench-scale high solids enzymatic hydrolysis was 77%, prior to the inclusion of any additional conversion that may occur during subsequent fermentation. This study effectively characterized a range of Pretreatment reaction conditions using deacetylated corn stover at low Acid loadings and identified an optimum reaction condition was selected and used in a series of integrated pilot scale cellulosic ethanol production campaigns. Additionally, several issues exist to be considered in future Pretreatment experiments in continuous reactor systems, including the formation of char within the reactor, as well as practical issues with feeding herbaceous feedstock into pressurized systems.
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the impacts of deacetylation prior to Dilute Acid Pretreatment on the bioethanol process
Biotechnology for Biofuels, 2012Co-Authors: Xiaowen Chen, David K Johnson, Joseph Shekiro, Mary Ann Franden, Wei Wang, Min Zhang, Erik M Kuhn, Melvin P. TuckerAbstract:Dilute Acid Pretreatment is a promising Pretreatment technology for the biochemical production of ethanol from lignocellulosic biomass. During Dilute Acid Pretreatment, xylan depolymerizes to form soluble xylose monomers and oligomers. Because the xylan found in nature is highly acetylated, the formation of xylose monomers requires two steps: 1) cleavage of the xylosidic bonds, and 2) cleavage of covalently bonded acetyl ester groups. In this study, we show that the latter may be the rate limiting step for xylose monomer formation. Furthermore, acetyl groups are also found to be a cause of biomass recalcitrance and hydrolyzate toxicity. While the removal of acetyl groups from native corn stover by alkaline de-esterification prior to Pretreatment improves overall process yields, the exact impact is highly dependent on the corn stover variety in use. Xylose monomer yields in Pretreatment generally increases by greater than 10%. Compared to pretreated corn stover controls, the deacetylated corn stover feedstock is approximately 20% more digestible after Pretreatment. Finally, by lowering hydrolyzate toxicity, xylose utilization and ethanol yields are further improved during fermentation by roughly 10% and 7%, respectively. In this study, several varieties of corn stover lots were investigated to test the robustness of the deacetylation-Pretreatment-saccharification-fermentation process. Deacetylation shows significant improvement on glucose and xylose yields during Pretreatment and enzymatic hydrolysis, but it also reduces hydrolyzate toxicity during fermentation, thereby improving ethanol yields and titer. The magnitude of effect is dependent on the selected corn stover variety, with several varieties achieving improvements of greater than 10% xylose yield in Pretreatment, 20% glucose yield in low solids enzymatic hydrolysis and 7% overall ethanol yield.
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improved xylan hydrolysis of corn stover by deacetylation with high solids Dilute Acid Pretreatment
Industrial & Engineering Chemistry Research, 2012Co-Authors: Xiaowen Chen, Joseph Shekiro, Rick Elander, Melvin P. TuckerAbstract:To produce ethanol cost-effectively from herbaceous feedstocks such as corn stover, efficient xylan hydrolysis with monomeric xylose yields approaching 90% are necessary. Dilute Acid Pretreatment is well established as one of the Pretreatment technologies for xylan hydrolysis; however, the accumulation of salts from neutralization, the production of toxic byproducts, and the release of acetic Acid can inhibit enzymatic saccharification and fermentation, resulting in depressed ethanol yields. Successful removal of acetyl groups from native corn stover by alkali de-esterification could potentially increase monomeric xylose yields from Pretreatment and enzymatic hydrolysis, improve cellulose digestibility, and reduce the cytotoxicity of the fermentation broth. Results presented in this article show that alkaline extraction removed significant amounts of acetyl groups from corn stover, improved xylan hydrolysis in high solids Dilute Acid Pretreatment by more than 50%, and improved xylan and glucan hydrolysis ...
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high xylose yields from Dilute Acid Pretreatment of corn stover under process relevant conditions
Applied Biochemistry and Biotechnology, 2009Co-Authors: Noah D Weiss, Melvin P. Tucker, Nicholas J Nagle, Rick ElanderAbstract:Pretreatment experiments were carried out to demonstrate high xylose yields at high solids loadings in two different batch Pretreatment reactors under process-relevant conditions. Corn stover was pretreated with Dilute sulfuric Acid using a 4-l Steam Digester and a 4-l stirred ZipperClave® reactor. Solids were loaded at 45% dry matter (wt/wt) after sulfuric Acid catalyst impregnation using nominal particle sizes of either 6 or 18 mm. Pretreatment was carried out at temperatures between 180 and 200 °C at residence times of either 90 or 105 s. Results demonstrate an ability to achieve high xylose yields (>80%) over a range of Pretreatment conditions, with performance showing little dependence on particle size or Pretreatment reactor type. The high xylose yields are attributed to effective catalyst impregnation and rapid rates of heat transfer during Pretreatment.
Rajeev Kumar - One of the best experts on this subject based on the ideXlab platform.
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carbohydrate derived pseudo lignin can retard cellulose biological conversion
Biotechnology and Bioengineering, 2013Co-Authors: Arthur J Ragauskas, Rajeev Kumar, Charles E. Wyman, Poulomi Sannigrahi, Seokwon JungAbstract:Dilute Acid as well as water only (hydrothermal) Pretreatments often lead to a significant hemicellulose loss to soluble furans and insoluble degradation products, collectively termed as chars and/or pseudo-lignin. In order to understand the factors contributing to reducing sugar yields from pretreated biomass and the possible influence of hemicellulose derived pseudo-lignin on cellulose conversion at the moderate to low enzyme loadings necessary for favorable economics, Dilute Acid Pretreatment of Avicel cellulose alone and mixed with beechwood xylan or xylose was performed at various severities. Following Pretreatment, the solids were enzymatically hydrolyzed and characterized for chemical composition and physical properties by NMR, FT-IR, and SEM imaging. It was found that hemicelluloses (xylan) derived-pseudo-lignin was formed at even moderate severities and that these insoluble degradation products can significantly retard cellulose hydrolysis. Furthermore, although low severity (CSF ~ 1.94) Dilute Acid Pretreatment of a xylan-Avicel mixture hydrolyzed most of the xylan (98%) and produced negligible amounts of pseudo-lignin, enzymatic conversion of cellulose dropped significantly (>25%) compared to cellulose pretreated alone at the same conditions. The drop in cellulose conversion was higher than realized for cellulase inhibition by xylooligomers reported previously. Plausible mechanisms are discussed to explain the observed reductions in cellulose conversions.
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Carbohydrate derived-pseudo-lignin can retard cellulose biological conversion.
Biotechnology and Bioengineering, 2012Co-Authors: Rajeev Kumar, Arthur J Ragauskas, Poulomi Sannigrahi, Seokwon Jung, Charles E. WymanAbstract:Dilute Acid as well as water only (hydrothermal) Pretreatments often lead to a significant hemicellulose loss to soluble furans and insoluble degradation products, collectively termed as chars and/or pseudo-lignin. In order to understand the factors contributing to reducing sugar yields from pretreated biomass and the possible influence of hemicellulose derived pseudo-lignin on cellulose conversion at the moderate to low enzyme loadings necessary for favorable economics, Dilute Acid Pretreatment of Avicel cellulose alone and mixed with beechwood xylan or xylose was performed at various severities. Following Pretreatment, the solids were enzymatically hydrolyzed and characterized for chemical composition and physical properties by NMR, FT-IR, and SEM imaging. It was found that hemicelluloses (xylan) derived-pseudo-lignin was formed at even moderate severities and that these insoluble degradation products can significantly retard cellulose hydrolysis. Furthermore, although low severity (CSF ∼ 1.94) Dilute Acid Pretreatment of a xylan–Avicel mixture hydrolyzed most of the xylan (98%) and produced negligible amounts of pseudo-lignin, enzymatic conversion of cellulose dropped significantly (>25%) compared to cellulose pretreated alone at the same conditions. The drop in cellulose conversion was higher than realized for cellulase inhibition by xylooligomers reported previously. Plausible mechanisms are discussed to explain the observed reductions in cellulose conversions. Biotechnol. Bioeng. 2013; 110: 737–753. © 2012 Wiley Periodicals, Inc.
Daniel J Schell - One of the best experts on this subject based on the ideXlab platform.
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characterization of pilot scale Dilute Acid Pretreatment performance using deacetylated corn stover
Biotechnology for Biofuels, 2014Co-Authors: Joseph Shekiro, Melvin P. Tucker, Rick Elander, Erik M Kuhn, Nicholas J Nagle, Daniel J SchellAbstract:Dilute Acid Pretreatment is a promising process technology for the deconstruction of low-lignin lignocellulosic biomass, capable of producing high yields of hemicellulosic sugars and enhancing enzymatic yields of glucose as part of a biomass-to-biofuels process. However, while it has been extensively studied, most work has historically been conducted at relatively high Acid concentrations of 1 - 4% (weight/weight). Reducing the effective Acid loading in Pretreatment has the potential to reduce chemical costs both for Pretreatment and subsequent neutralization. Additionally, if Acid loadings are sufficiently low, capital requirements associated with reactor construction may be significantly reduced due to the relaxation of requirements for exotic alloys. Despite these benefits, past efforts have had difficulty obtaining high process yields at low Acid loadings without supplementation of additional unit operations, such as mechanical refining. Recently, we optimized the Dilute Acid Pretreatment of deacetylated corn stover at low Acid loadings in a 1-ton per day horizontal Pretreatment reactor. This effort included more than 25 pilot-scale Pretreatment experiments executed at reactor temperatures ranging from 150 – 170°C, residence times of 10 – 20 minutes and hydrolyzer sulfuric Acid concentrations between 0.15 – 0.30% (weight/weight). In addition to characterizing the process yields achieved across the reaction space, the optimization identified a Pretreatment reaction condition that achieved total xylose yields from Pretreatment of 73.5% ± 1.5% with greater than 97% xylan component balance closure across a series of five runs at the same condition. Feedstock reactivity at this reaction condition after bench-scale high solids enzymatic hydrolysis was 77%, prior to the inclusion of any additional conversion that may occur during subsequent fermentation. This study effectively characterized a range of Pretreatment reaction conditions using deacetylated corn stover at low Acid loadings and identified an optimum reaction condition was selected and used in a series of integrated pilot scale cellulosic ethanol production campaigns. Additionally, several issues exist to be considered in future Pretreatment experiments in continuous reactor systems, including the formation of char within the reactor, as well as practical issues with feeding herbaceous feedstock into pressurized systems.
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impact of corn stover composition on hemicellulose conversion during Dilute Acid Pretreatment and enzymatic cellulose digestibility of the pretreated solids
Bioresource Technology, 2010Co-Authors: Noah D Weiss, Joseph D Farmer, Daniel J SchellAbstract:This study assessed the impact of corn stover compositional variability on xylose conversion yields during Dilute Acid Pretreatment and on enzymatic cellulose digestibility of the resulting pretreated solids. Seven compositionally-different stovers obtained from various locations throughout the United States were pretreated at three different conditions in triplicate in a pilot-scale continuous reactor. At the same Pretreatment severity, a 2-fold increase in monomeric xylose yield and a 1.5-fold increase in enzymatic cellulose digestibility from their lowest values were found. Similar results were observed at the other Pretreatment conditions. It was found that xylose conversion yields decreased with increasing Acid neutralization capacity or soil content of the corn stover. Xylose yields also increased with increasing xylan content. No other significant correlations between corn stover's component concentrations and conversion yields were found.
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Dilute Acid Pretreatment of softwoods
Applied Biochemistry and Biotechnology, 1998Co-Authors: Quang A. Nguyen, Melvin P. Tucker, Fred A. Keller, Brian L Boynton, Daniel J SchellAbstract:Selective thinning of forests in the western United States will generate a large, sustainable quantity of softwood residues that can be an attractive feedstock for fuel ethanol production. The major species available from thinning of forests in northern California and the eastern Rocky Mountains include white fir (Abies concolor), Douglas fir (Pseudotsuga menziesii), and Ponderosa pine (Pinus ponderosa). Douglas fir chips were soaked in 0.4% sulfuric Acid solution, then pretreated with steam at 200 – 230°C for 1 – 5 min. After Pretreatment, 90 – 95% of the hemicellulose and as much as 20% of the cellulose was solubilized in water, and 90% of the remaining cellulose can be hydrolyzed to glucose by cellulase enzyme. The prehydrolysates, at as high as 10% total solid concentration, can be readily fermented by the unadapted yeastSaccharomyces cerevisiae D5A.