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Chandel AK, Antunes FAF, Anjos V, Bell MJV, Rodrigues LN, Polikarpov I, de Azevedo ER, Bernardinelli OD, Rosa CA, Pagnocca FC, da Silva SS. Multi-scale structural and chemical analysis of sugarcane bagasse in the process of sequential acid-base pretreatment and ethanol production by Scheffersomyces shehatae and Saccharomyces cerevisiae. BIOTECHNOLOGY FOR BIOFUELS 2014; 7:63. [PMID: 24739736 PMCID: PMC4005856 DOI: 10.1186/1754-6834-7-63] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/09/2013] [Accepted: 02/04/2014] [Indexed: 05/04/2023]
Abstract
BACKGROUND Heavy usage of gasoline, burgeoning fuel prices, and environmental issues have paved the way for the exploration of cellulosic ethanol. Cellulosic ethanol production technologies are emerging and require continued technological advancements. One of the most challenging issues is the pretreatment of lignocellulosic biomass for the desired sugars yields after enzymatic hydrolysis. We hypothesized that consecutive dilute sulfuric acid-dilute sodium hydroxide pretreatment would overcome the native recalcitrance of sugarcane bagasse (SB) by enhancing cellulase accessibility of the embedded cellulosic microfibrils. RESULTS SB hemicellulosic hydrolysate after concentration by vacuum evaporation and detoxification showed 30.89 g/l xylose along with other products (0.32 g/l glucose, 2.31 g/l arabinose, and 1.26 g/l acetic acid). The recovered cellulignin was subsequently delignified by sodium hydroxide mediated pretreatment. The acid-base pretreated material released 48.50 g/l total reducing sugars (0.91 g sugars/g cellulose amount in SB) after enzymatic hydrolysis. Ultra-structural mapping of acid-base pretreated and enzyme hydrolyzed SB by microscopic analysis (scanning electron microcopy (SEM), transmitted light microscopy (TLM), and spectroscopic analysis (X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, Fourier transform near-infrared (FT-NIR) spectroscopy, and nuclear magnetic resonance (NMR) spectroscopy) elucidated the molecular changes in hemicellulose, cellulose, and lignin components of bagasse. The detoxified hemicellulosic hydrolysate was fermented by Scheffersomyces shehatae (syn. Candida shehatae UFMG HM 52.2) and resulted in 9.11 g/l ethanol production (yield 0.38 g/g) after 48 hours of fermentation. Enzymatic hydrolysate when fermented by Saccharomyces cerevisiae 174 revealed 8.13 g/l ethanol (yield 0.22 g/g) after 72 hours of fermentation. CONCLUSIONS Multi-scale structural studies of SB after sequential acid-base pretreatment and enzymatic hydrolysis showed marked changes in hemicellulose and lignin removal at molecular level. The cellulosic material showed high saccharification efficiency after enzymatic hydrolysis. Hemicellulosic and cellulosic hydrolysates revealed moderate ethanol production by S. shehatae and S. cerevisiae under batch fermentation conditions.
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Affiliation(s)
- Anuj K Chandel
- Department of Biotechnology, School of Engineering of Lorena, Estrada Municipal do Campinho, University of São Paulo, Caixa Postal 116 12.602.810, Lorena, São Paulo, Brazil
| | - Felipe AF Antunes
- Department of Biotechnology, School of Engineering of Lorena, Estrada Municipal do Campinho, University of São Paulo, Caixa Postal 116 12.602.810, Lorena, São Paulo, Brazil
| | - Virgilio Anjos
- Materials Spectroscopy Laboratory, Department of Physics, Federal University of Juiz de Fora, Juiz de Fora 36036-330 Minas Gerais, Brazil
| | - Maria JV Bell
- Materials Spectroscopy Laboratory, Department of Physics, Federal University of Juiz de Fora, Juiz de Fora 36036-330 Minas Gerais, Brazil
| | - Leonarde N Rodrigues
- Materials Spectroscopy Laboratory, Department of Physics, Federal University of Juiz de Fora, Juiz de Fora 36036-330 Minas Gerais, Brazil
| | - Igor Polikarpov
- Instituto de Física de São Carlos, Universidade de São Paulo, Caixa Postal 369, São Carlos, São Paulo CEP 13560-970, Brazil
| | - Eduardo R de Azevedo
- Instituto de Física de São Carlos, Universidade de São Paulo, Caixa Postal 369, São Carlos, São Paulo CEP 13560-970, Brazil
| | - Oigres D Bernardinelli
- Instituto de Física de São Carlos, Universidade de São Paulo, Caixa Postal 369, São Carlos, São Paulo CEP 13560-970, Brazil
| | - Carlos A Rosa
- Departmento de Microbiologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil
| | - Fernando C Pagnocca
- Department of Biochemistry and Microbiology, Institute of Biosciences, CIES/UNESP, Rio Claro, São Paulo, Brazil
| | - Silvio S da Silva
- Department of Biotechnology, School of Engineering of Lorena, Estrada Municipal do Campinho, University of São Paulo, Caixa Postal 116 12.602.810, Lorena, São Paulo, Brazil
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Wolfrum EJ, Ness RM, Nagle NJ, Peterson DJ, Scarlata CJ. A laboratory-scale pretreatment and hydrolysis assay for determination of reactivity in cellulosic biomass feedstocks. BIOTECHNOLOGY FOR BIOFUELS 2013; 6:162. [PMID: 24229321 PMCID: PMC4176505 DOI: 10.1186/1754-6834-6-162] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/07/2013] [Accepted: 10/28/2013] [Indexed: 05/18/2023]
Abstract
BACKGROUND The rapid determination of the release of structural sugars from biomass feedstocks is an important enabling technology for the development of cellulosic biofuels. An assay that is used to determine sugar release for large numbers of samples must be robust, rapid, and easy to perform, and must use modest amounts of the samples to be tested.In this work we present a laboratory-scale combined pretreatment and saccharification assay that can be used as a biomass feedstock screening tool. The assay uses a commercially available automated solvent extraction system for pretreatment followed by a small-scale enzymatic hydrolysis step. The assay allows multiple samples to be screened simultaneously, and uses only ~3 g of biomass per sample. If the composition of the biomass sample is known, the results of the assay can be expressed as reactivity (fraction of structural carbohydrate present in the biomass sample released as monomeric sugars). RESULTS We first present pretreatment and enzymatic hydrolysis experiments on a set of representative biomass feedstock samples (corn stover, poplar, sorghum, switchgrass) in order to put the assay in context, and then show the results of the assay applied to approximately 150 different feedstock samples covering 5 different materials. From the compositional analysis data we identify a positive correlation between lignin and structural carbohydrates, and from the reactivity data we identify a negative correlation between both carbohydrate and lignin content and total reactivity. The negative correlation between lignin content and total reactivity suggests that lignin may interfere with sugar release, or that more mature samples (with higher structural sugars) may have more recalcitrant lignin. CONCLUSIONS The assay presented in this work provides a robust and straightforward method to measure the sugar release after pretreatment and saccharification that can be used as a biomass feedstock screening tool. We demonstrated the utility of the assay by identifying correlations between feedstock composition and reactivity in a population of 150 samples.
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Affiliation(s)
- Edward J Wolfrum
- National Bioenergy Center, National Renewable Energy Laboratory, 15013 Denver West Parkway, Golden, CO 80401, USA
| | - Ryan M Ness
- National Bioenergy Center, National Renewable Energy Laboratory, 15013 Denver West Parkway, Golden, CO 80401, USA
| | - Nicholas J Nagle
- National Bioenergy Center, National Renewable Energy Laboratory, 15013 Denver West Parkway, Golden, CO 80401, USA
| | - Darren J Peterson
- National Bioenergy Center, National Renewable Energy Laboratory, 15013 Denver West Parkway, Golden, CO 80401, USA
| | - Christopher J Scarlata
- National Bioenergy Center, National Renewable Energy Laboratory, 15013 Denver West Parkway, Golden, CO 80401, USA
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Sanchez-Vazquez SA, Hailes HC, Evans JRG. Hydrophobic Polymers from Food Waste: Resources and Synthesis. POLYM REV 2013. [DOI: 10.1080/15583724.2013.834933] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Burkhardt S, Kumar L, Chandra R, Saddler J. How effective are traditional methods of compositional analysis in providing an accurate material balance for a range of softwood derived residues? BIOTECHNOLOGY FOR BIOFUELS 2013; 6:90. [PMID: 23800175 PMCID: PMC3704954 DOI: 10.1186/1754-6834-6-90] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/26/2013] [Accepted: 06/11/2013] [Indexed: 05/03/2023]
Abstract
BACKGROUND Forest residues represent an abundant and sustainable source of biomass which could be used as a biorefinery feedstock. Due to the heterogeneity of forest residues, such as hog fuel and bark, one of the expected challenges is to obtain an accurate material balance of these feedstocks. Current compositional analytical methods have been standardised for more homogenous feedstocks such as white wood and agricultural residues. The described work assessed the accuracy of existing and modified methods on a variety of forest residues both before and after a typical pretreatment process. RESULTS When "traditional" pulp and paper methods were used, the total amount of material that could be quantified in each of the six softwood-derived residues ranged from 88% to 96%. It was apparent that the extractives present in the substrate were most influential in limiting the accuracy of a more representative material balance. This was particularly evident when trying to determine the lignin content, due to the incomplete removal of the extractives, even after a two stage water-ethanol extraction. Residual extractives likely precipitated with the acid insoluble lignin during analysis, contributing to an overestimation of the lignin content. Despite the minor dissolution of hemicellulosic sugars, extraction with mild alkali removed most of the extractives from the bark and improved the raw material mass closure to 95% in comparison to the 88% value obtained after water-ethanol extraction. After pretreatment, the extent of extractive removal and their reaction/precipitation with lignin was heavily dependent on the pretreatment conditions used. The selective removal of extractives and their quantification after a pretreatment proved to be even more challenging. Regardless of the amount of extractives that were originally present, the analytical methods could be refined to provide reproducible quantification of the carbohydrates present in both the starting material and after pretreatment. CONCLUSION Despite the challenges resulting from the heterogeneity of the initial biomass substrates a reasonable summative mass closure could be obtained before and after steam pretreatment. However, method revision and optimisation was required, particularly the effective removal of extractives, to ensure that representative and reproducible values for the major lignin and carbohydrate components.
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Affiliation(s)
- Sabrina Burkhardt
- Forest Products Biotechnology/Bioenergy, 2424 Main Mall University of British Columbia, Greater Vancouver, Canada
| | - Linoj Kumar
- Forest Products Biotechnology/Bioenergy, 2424 Main Mall University of British Columbia, Greater Vancouver, Canada
| | - Richard Chandra
- Forest Products Biotechnology/Bioenergy, 2424 Main Mall University of British Columbia, Greater Vancouver, Canada
| | - Jack Saddler
- Forest Products Biotechnology/Bioenergy, 2424 Main Mall University of British Columbia, Greater Vancouver, Canada
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Lima MA, Lavorente GB, da Silva HKP, Bragatto J, Rezende CA, Bernardinelli OD, deAzevedo ER, Gomez LD, McQueen-Mason SJ, Labate CA, Polikarpov I. Effects of pretreatment on morphology, chemical composition and enzymatic digestibility of eucalyptus bark: a potentially valuable source of fermentable sugars for biofuel production - part 1. BIOTECHNOLOGY FOR BIOFUELS 2013; 6:75. [PMID: 23657132 PMCID: PMC3667114 DOI: 10.1186/1754-6834-6-75] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/04/2012] [Accepted: 04/26/2013] [Indexed: 05/04/2023]
Abstract
BACKGROUND In recent years, the growing demand for biofuels has encouraged the search for different sources of underutilized lignocellulosic feedstocks that are available in sufficient abundance to be used for sustainable biofuel production. Much attention has been focused on biomass from grass. However, large amounts of timber residues such as eucalyptus bark are available and represent a potential source for conversion to bioethanol. In the present paper, we investigate the effects of a delignification process with increasing sodium hydroxide concentrations, preceded or not by diluted acid, on the bark of two eucalyptus clones: Eucalyptus grandis (EG) and the hybrid, E. grandis x urophylla (HGU). The enzymatic digestibility and total cellulose conversion were measured, along with the effect on the composition of the solid and the liquor fractions. Barks were also assessed using Fourier-transform infrared spectroscopy (FTIR), solid-state nuclear magnetic resonance (NMR), X-Ray diffraction, and scanning electron microscopy (SEM). RESULTS Compositional analysis revealed an increase in the cellulose content, reaching around 81% and 76% of glucose for HGU and EG, respectively, using a two-step treatment with HCl 1%, followed by 4% NaOH. Lignin removal was 84% (HGU) and 79% (EG), while the hemicellulose removal was 95% and 97% for HGU and EG, respectively. However, when we applied a one-step treatment, with 4% NaOH, higher hydrolysis efficiencies were found after 48 h for both clones, reaching almost 100% for HGU and 80% for EG, in spite of the lower lignin and hemicellulose removal. Total cellulose conversion increased from 5% and 7% to around 65% for HGU and 59% for EG. NMR and FTIR provided important insight into the lignin and hemicellulose removal and SEM studies shed light on the cell-wall unstructuring after pretreatment and lignin migration and precipitation on the fibers surface, which explain the different hydrolysis rates found for the clones. CONCLUSION Our results show that the single step alkaline pretreatment improves the enzymatic digestibility of Eucalyptus bark. Furthermore, the chemical and physical methods combined in this study provide a better comprehension of the pretreatment effects on cell-wall and the factors that influence enzymatic digestibility of this forest residue.
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Affiliation(s)
- Marisa A Lima
- Instituto de Física de São Carlos, Universidade de São Paulo, Caixa Postal 369, 13560-970, São Carlos, SP, Brazil
| | - Gabriela B Lavorente
- Laboratório Max Feffer de Genética de Plantas, Departamento de Genética - ESALQ, Universidade de São Paulo, Caixa Postal 83, 13418-900, Piracicaba, SP, Brazil
| | - Hana KP da Silva
- Laboratório Max Feffer de Genética de Plantas, Departamento de Genética - ESALQ, Universidade de São Paulo, Caixa Postal 83, 13418-900, Piracicaba, SP, Brazil
| | - Juliano Bragatto
- Laboratório Max Feffer de Genética de Plantas, Departamento de Genética - ESALQ, Universidade de São Paulo, Caixa Postal 83, 13418-900, Piracicaba, SP, Brazil
| | - Camila A Rezende
- Instituto de Física de São Carlos, Universidade de São Paulo, Caixa Postal 369, 13560-970, São Carlos, SP, Brazil
| | - Oigres D Bernardinelli
- Instituto de Física de São Carlos, Universidade de São Paulo, Caixa Postal 369, 13560-970, São Carlos, SP, Brazil
| | - Eduardo R deAzevedo
- Instituto de Física de São Carlos, Universidade de São Paulo, Caixa Postal 369, 13560-970, São Carlos, SP, Brazil
| | - Leonardo D Gomez
- CNAP, Department of Biology, University of York, Heslington, York YO10 5YW, UK
| | | | - Carlos A Labate
- Laboratório Max Feffer de Genética de Plantas, Departamento de Genética - ESALQ, Universidade de São Paulo, Caixa Postal 83, 13418-900, Piracicaba, SP, Brazil
| | - Igor Polikarpov
- Instituto de Física de São Carlos, Universidade de São Paulo, Caixa Postal 369, 13560-970, São Carlos, SP, Brazil
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Liu Z, Padmanabhan S, Cheng K, Schwyter P, Pauly M, Bell AT, Prausnitz JM. Aqueous-ammonia delignification of miscanthus followed by enzymatic hydrolysis to sugars. BIORESOURCE TECHNOLOGY 2013; 135:23-29. [PMID: 23257277 DOI: 10.1016/j.biortech.2012.10.133] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/28/2012] [Revised: 10/25/2012] [Accepted: 10/26/2012] [Indexed: 06/01/2023]
Abstract
This work concerns the effect of aqueous ammonia pretreatment at four temperatures and at 10, 20 or 30 wt.% ammonia. After 1h, more than 65% delignification is achieved at 150 or 180 °C for high and for low concentrations of ammonia. When the delignified miscanthus is enzymatically hydrolyzed for 96 h using cellulases and beta-glucosidase, conversion of the recovered solid to glucose is 53.4% and to xylose 70.0%. Additional glucose and xylose can be obtained from the ammonia-containing aqueous phase. Increased ammonia concentration leads to better conversion. Fourier-transform infrared and Two-dimensional (13)C-(1)H Heteronuclear Single Quantum Coherence (HSQC) Nuclear Magnetic Resonance spectroscopy provide data for the composition of the pretreated miscanthus and for that of the liquid extract. These spectra indicate that pretreatment with ammonia leads to de-acetylation of the xylan-backbone. The β-O-4' linked aryl ether remains the most abundant linkage in the pretreated miscanthus.
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Affiliation(s)
- Zhongguo Liu
- Energy Biosciences Institute, University of California at Berkeley, CA 94720-1462, USA
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Chandel AK, Antunes FAF, Silva MB, da Silva SS. Unraveling the structure of sugarcane bagasse after soaking in concentrated aqueous ammonia (SCAA) and ethanol production by Scheffersomyces (Pichia) stipitis. BIOTECHNOLOGY FOR BIOFUELS 2013; 6:102. [PMID: 23856012 PMCID: PMC3720555 DOI: 10.1186/1754-6834-6-102] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/15/2013] [Accepted: 07/02/2013] [Indexed: 05/14/2023]
Abstract
BACKGROUND Fuel ethanol production from sustainable and largely abundant agro-residues such as sugarcane bagasse (SB) provides long term, geopolitical and strategic benefits. Pretreatment of SB is an inevitable process for improved saccharification of cell wall carbohydrates. Recently, ammonium hydroxide-based pretreatment technologies have gained significance as an effective and economical pretreatment strategy. We hypothesized that soaking in concentrated aqueous ammonia-mediated thermochemical pretreatment (SCAA) would overcome the native recalcitrance of SB by enhancing cellulase accessibility of the embedded holocellulosic microfibrils. RESULTS In this study, we designed an experiment considering response surface methodology (Taguchi method, L8 orthogonal array) to optimize sugar recovery from ammonia pretreated sugarcane bagasse (SB) by using the method of soaking in concentrated aqueous ammonia (SCAA-SB). Three independent variables: ammonia concentration, temperature and time, were selected at two levels with center point. The ammonia pretreated bagasse (SCAA-SB) was enzymatically hydrolysed by commercial enzymes (Celluclast 1.5 L and Novozym 188) using 15 FPU/g dry biomass and 17.5 Units of β-glucosidase/g dry biomass at 50°C, 150 rpm for 96 h. A maximum of 28.43 g/l reducing sugars corresponding to 0.57 g sugars/g pretreated bagasse was obtained from the SCAA-SB derived using a 20% v/v ammonia solution, at 70°C for 24 h after enzymatic hydrolysis. Among the tested parameters, pretreatment time showed the maximum influence (p value, 0.053282) while ammonia concentration showed the least influence (p value, 0.612552) on sugar recovery. The changes in the ultra-structure and crystallinity of native SCAA-SB and enzymatically hydrolysed SB were observed by scanning electron microscopy (SEM), x-ray diffraction (XRD) and solid-state (13)C nuclear magnetic resonance (NMR) spectroscopy. The enzymatic hydrolysates and solid SCAA-SB were subjected to ethanol fermentation under separate hydrolysis and fermentation (SHF) and simultaneous saccharification and fermentation (SSF) by Scheffersomyces (Pichia) stipitis NRRL Y-7124 respectively. Higher ethanol production (10.31 g/l and yield, 0.387 g/g) was obtained through SSF than SHF (3.83 g/l and yield, 0.289 g/g). CONCLUSIONS SCAA treatment showed marked lignin removal from SB thus improving the accessibility of cellulases towards holocellulose substrate as evidenced by efficient sugar release. The ultrastructure of SB after SCAA and enzymatic hydrolysis of holocellulose provided insights of the degradation process at the molecular level.
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Affiliation(s)
- Anuj K Chandel
- Department of Biotechnology, Engineering School of Lorena, University of São Paulo, Lorena 116-12.602.810, Sao Paulo, Brazil
| | - Felipe AF Antunes
- Department of Biotechnology, Engineering School of Lorena, University of São Paulo, Lorena 116-12.602.810, Sao Paulo, Brazil
| | - Messias B Silva
- Department of Chemical Engineering, Engineering School of Lorena, University of São Paulo, Lorena 12.602.810, Sao Paulo, Brazil
| | - Silvio Silvério da Silva
- Department of Biotechnology, Engineering School of Lorena, University of São Paulo, Lorena 116-12.602.810, Sao Paulo, Brazil
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Templeton DW, Quinn M, Van Wychen S, Hyman D, Laurens LM. Separation and quantification of microalgal carbohydrates. J Chromatogr A 2012. [DOI: 10.1016/j.chroma.2012.10.034] [Citation(s) in RCA: 123] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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59
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Deutschmann R, Dekker RF. From plant biomass to bio-based chemicals: Latest developments in xylan research. Biotechnol Adv 2012; 30:1627-40. [DOI: 10.1016/j.biotechadv.2012.07.001] [Citation(s) in RCA: 195] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2012] [Revised: 06/12/2012] [Accepted: 07/01/2012] [Indexed: 11/26/2022]
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Monono EM, Haagenson DM, Pryor SW. Developing and Evaluating NIR Calibration Models for Multi-Species Herbaceous Perennials. Ind Biotechnol (New Rochelle N Y) 2012. [DOI: 10.1089/ind.2012.0018] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Affiliation(s)
- Ewumbua M. Monono
- Department of Agricultural and Biosystems Engineering, North Dakota State University, Fargo, ND
| | - Darrin M. Haagenson
- Department of Agricultural and Biosystems Engineering, North Dakota State University, Fargo, ND
| | - Scott W. Pryor
- Department of Agricultural and Biosystems Engineering, North Dakota State University, Fargo, ND
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Chen X, Tao L, Shekiro J, Mohaghaghi A, Decker S, Wang W, Smith H, Park S, Himmel ME, Tucker M. Improved ethanol yield and reduced Minimum Ethanol Selling Price (MESP) by modifying low severity dilute acid pretreatment with deacetylation and mechanical refining: 1) Experimental. BIOTECHNOLOGY FOR BIOFUELS 2012; 5:60. [PMID: 22888758 PMCID: PMC3519810 DOI: 10.1186/1754-6834-5-60] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2012] [Accepted: 08/07/2012] [Indexed: 05/03/2023]
Abstract
BACKGROUND Historically, acid pretreatment technology for the production of bio-ethanol from corn stover has required severe conditions to overcome biomass recalcitrance. However, the high usage of acid and steam at severe pretreatment conditions hinders the economic feasibility of the ethanol production from biomass. In addition, the amount of acetate and furfural produced during harsh pretreatment is in the range that strongly inhibits cell growth and impedes ethanol fermentation. The current work addresses these issues through pretreatment with lower acid concentrations and temperatures incorporated with deacetylation and mechanical refining. RESULTS The results showed that deacetylation with 0.1 M NaOH before acid pretreatment improved the monomeric xylose yield in pretreatment by up to 20% while keeping the furfural yield under 2%. Deacetylation also improved the glucose yield by 10% and the xylose yield by 20% during low solids enzymatic hydrolysis. Mechanical refining using a PFI mill further improved sugar yields during both low- and high-solids enzymatic hydrolysis. Mechanical refining also allowed enzyme loadings to be reduced while maintaining high yields. Deacetylation and mechanical refining are shown to assist in achieving 90% cellulose yield in high-solids (20%) enzymatic hydrolysis. When fermentations were performed under pH control to evaluate the effect of deacetylation and mechanical refining on the ethanol yields, glucose and xylose utilizations over 90% and ethanol yields over 90% were achieved. Overall ethanol yields were calculated based on experimental results for the base case and modified cases. One modified case that integrated deacetylation, mechanical refining, and washing was estimated to produce 88 gallons of ethanol per ton of biomass. CONCLUSION The current work developed a novel bio-ethanol process that features pretreatment with lower acid concentrations and temperatures incorporated with deacetylation and mechanical refining. The new process shows improved overall ethanol yields compared to traditional dilute acid pretreatment. The experimental results from this work support the techno-economic analysis and calculation of Minimum Ethanol Selling Price (MESP) detailed in our companion paper.
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Affiliation(s)
- Xiaowen Chen
- National Bioenergy Center, National Renewable Energy Lab, 1617 Cole Blvd, Golden, CO, 80127, USA
| | - Ling Tao
- National Bioenergy Center, National Renewable Energy Lab, 1617 Cole Blvd, Golden, CO, 80127, USA
| | - Joseph Shekiro
- National Bioenergy Center, National Renewable Energy Lab, 1617 Cole Blvd, Golden, CO, 80127, USA
| | - Ali Mohaghaghi
- National Bioenergy Center, National Renewable Energy Lab, 1617 Cole Blvd, Golden, CO, 80127, USA
| | - Steve Decker
- Bioscience Center, National Renewable Energy Lab, 1617 Cole Blvd, Golden, CO, 80127, USA
| | - Wei Wang
- Bioscience Center, National Renewable Energy Lab, 1617 Cole Blvd, Golden, CO, 80127, USA
| | - Holly Smith
- National Bioenergy Center, National Renewable Energy Lab, 1617 Cole Blvd, Golden, CO, 80127, USA
| | - Sunkyu Park
- Department of Forest Biomaterials, North Carolina State University, 2820 Faucette Drive, Raleigh, NC, 27695, USA
| | - Michael E Himmel
- Bioscience Center, National Renewable Energy Lab, 1617 Cole Blvd, Golden, CO, 80127, USA
| | - Melvin Tucker
- National Bioenergy Center, National Renewable Energy Lab, 1617 Cole Blvd, Golden, CO, 80127, USA
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Enzymatic conversion of xylan residues from dilute acid-pretreated corn stover. Appl Biochem Biotechnol 2012; 168:421-33. [PMID: 22847186 PMCID: PMC3458197 DOI: 10.1007/s12010-012-9786-5] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2011] [Accepted: 06/28/2012] [Indexed: 11/19/2022]
Abstract
Enzymatic conversion of oligomeric xylose and insoluble xylan remaining after effective pretreatment offers significant potential to improve xylan-to-xylose yields while minimizing yields of degredation products and fermentation inhibitors. In this work, a commercial enzyme cocktail is demonstrated to convert up to 70 % of xylo-oligomers found in dilute acid-pretreated hydrolyzate liquor at varying levels of dilution when supplemented with accessory enzymes targeting common side chains. Commercial enzyme cocktails are also shown to convert roughly 80 % of insoluble xylan remaining after effective high-solids, dilute acid pretreatment.
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Cellulose degradation by Sulfolobus solfataricus requires a cell-anchored endo-β-1-4-glucanase. J Bacteriol 2012; 194:5091-100. [PMID: 22821975 DOI: 10.1128/jb.00672-12] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
A sequence encoding a putative extracellular endoglucanase (sso1354) was identified in the complete genome sequence of Sulfolobus solfataricus. The encoded protein shares signature motifs with members of glycoside hydrolases family 12. After an unsuccessful first attempt at cloning the full-length coding sequences in Escherichia coli, an active but unstable recombinant enzyme lacking a 27-residue N-terminal sequence was generated. This 27-amino-acid sequence shows significant similarity with corresponding regions in the sugar binding proteins AraS, GlcS, and TreS of S. solfataricus that are responsible for anchoring them to the plasma membrane. A strategy based on an effective vector/host genetic system for Sulfolobus and on expression control by the promoter of the S. solfataricus gene which encodes the glucose binding protein allowed production of the enzyme in sufficient quantities for study. In fact, the enzyme expressed in S. solfataricus was stable and highly thermoresistant and showed optimal activity at low pH and high temperature. The protein was detected mainly in the plasma membrane fraction, confirming the structural similarity to the sugar binding proteins. The results of the protein expression in the two different hosts showed that the SSO1354 enzyme is endowed with an endo-β-1-4-glucanase activity and specifically hydrolyzes cellulose. Moreover, it also shows significant but distinguishable specificity toward several other sugar polymers, such as lichenan, xylan, debranched arabinan, pachyman, and curdlan.
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Vicari KJ, Tallam SS, Shatova T, Joo KK, Scarlata CJ, Humbird D, Wolfrum EJ, Beckham GT. Uncertainty in techno-economic estimates of cellulosic ethanol production due to experimental measurement uncertainty. BIOTECHNOLOGY FOR BIOFUELS 2012; 5:23. [PMID: 22507382 PMCID: PMC3503575 DOI: 10.1186/1754-6834-5-23] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/12/2012] [Accepted: 03/29/2012] [Indexed: 05/09/2023]
Abstract
BACKGROUND Cost-effective production of lignocellulosic biofuels remains a major financial and technical challenge at the industrial scale. A critical tool in biofuels process development is the techno-economic (TE) model, which calculates biofuel production costs using a process model and an economic model. The process model solves mass and energy balances for each unit, and the economic model estimates capital and operating costs from the process model based on economic assumptions. The process model inputs include experimental data on the feedstock composition and intermediate product yields for each unit. These experimental yield data are calculated from primary measurements. Uncertainty in these primary measurements is propagated to the calculated yields, to the process model, and ultimately to the economic model. Thus, outputs of the TE model have a minimum uncertainty associated with the uncertainty in the primary measurements. RESULTS We calculate the uncertainty in the Minimum Ethanol Selling Price (MESP) estimate for lignocellulosic ethanol production via a biochemical conversion process: dilute sulfuric acid pretreatment of corn stover followed by enzymatic hydrolysis and co-fermentation of the resulting sugars to ethanol. We perform a sensitivity analysis on the TE model and identify the feedstock composition and conversion yields from three unit operations (xylose from pretreatment, glucose from enzymatic hydrolysis, and ethanol from fermentation) as the most important variables. The uncertainty in the pretreatment xylose yield arises from multiple measurements, whereas the glucose and ethanol yields from enzymatic hydrolysis and fermentation, respectively, are dominated by a single measurement: the fraction of insoluble solids (fIS) in the biomass slurries. CONCLUSIONS We calculate a $0.15/gal uncertainty in MESP from the TE model due to uncertainties in primary measurements. This result sets a lower bound on the error bars of the TE model predictions. This analysis highlights the primary measurements that merit further development to reduce the uncertainty associated with their use in TE models. While we develop and apply this mathematical framework to a specific biorefinery scenario here, this analysis can be readily adapted to other types of biorefining processes and provides a general framework for propagating uncertainty due to analytical measurements through a TE model.
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Affiliation(s)
- Kristin J Vicari
- David H. Koch School of Chemical Engineering Practice, Massachusetts Institute of Technology, Cambridge, MA, USA
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Sai Sandeep Tallam
- David H. Koch School of Chemical Engineering Practice, Massachusetts Institute of Technology, Cambridge, MA, USA
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Tatyana Shatova
- David H. Koch School of Chemical Engineering Practice, Massachusetts Institute of Technology, Cambridge, MA, USA
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Koh Kang Joo
- David H. Koch School of Chemical Engineering Practice, Massachusetts Institute of Technology, Cambridge, MA, USA
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA
| | | | - David Humbird
- National Bioenergy Center, National Renewable Energy Laboratory, Golden, CO, USA
| | - Edward J Wolfrum
- National Bioenergy Center, National Renewable Energy Laboratory, Golden, CO, USA
| | - Gregg T Beckham
- National Bioenergy Center, National Renewable Energy Laboratory, Golden, CO, USA
- Department of Chemical Engineering, Colorado School of Mines, Golden, CO, USA
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Wei H, Tucker MP, Baker JO, Harris M, Luo Y, Xu Q, Himmel ME, Ding SY. Tracking dynamics of plant biomass composting by changes in substrate structure, microbial community, and enzyme activity. BIOTECHNOLOGY FOR BIOFUELS 2012; 5:20. [PMID: 22490508 PMCID: PMC3384452 DOI: 10.1186/1754-6834-5-20] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/12/2012] [Accepted: 04/10/2012] [Indexed: 05/07/2023]
Abstract
BACKGROUND Understanding the dynamics of the microbial communities that, along with their secreted enzymes, are involved in the natural process of biomass composting may hold the key to breaking the major bottleneck in biomass-to-biofuels conversion technology, which is the still-costly deconstruction of polymeric biomass carbohydrates to fermentable sugars.However, the complexity of both the structure of plant biomass and its counterpart microbial degradation communities makes it difficult to investigate the composting process. RESULTS In this study, a composter was set up with a mix of yellow poplar (Liriodendron tulipifera) wood-chips and mown lawn grass clippings (85:15 in dry-weight) and used as a model system. The microbial rDNA abundance data obtained from analyzing weekly-withdrawn composted samples suggested population-shifts from bacteria-dominated to fungus-dominated communities. Further analyses by an array of optical microscopic, transcriptional and enzyme-activity techniques yielded correlated results, suggesting that such population shifts occurred along with early removal of hemicellulose followed by attack on the consequently uncovered cellulose as the composting progressed. CONCLUSION The observed shifts in dominance by representative microbial groups, along with the observed different patterns in the gene expression and enzymatic activities between cellulases, hemicellulases, and ligninases during the composting process, provide new perspectives for biomass-derived biotechnology such as consolidated bioprocessing (CBP) and solid-state fermentation for the production of cellulolytic enzymes and biofuels.
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Affiliation(s)
- Hui Wei
- Biosciences Center, National Renewable Energy Laboratory, Golden, CO 80401, USA
| | - Melvin P Tucker
- National Bioenergy Center, National Renewable Energy Laboratory, Golden, CO 80401, USA
| | - John O Baker
- Biosciences Center, National Renewable Energy Laboratory, Golden, CO 80401, USA
| | - Michelle Harris
- Biosciences Center, National Renewable Energy Laboratory, Golden, CO 80401, USA
| | - Yonghua Luo
- Biosciences Center, National Renewable Energy Laboratory, Golden, CO 80401, USA
| | - Qi Xu
- Biosciences Center, National Renewable Energy Laboratory, Golden, CO 80401, USA
| | - Michael E Himmel
- Biosciences Center, National Renewable Energy Laboratory, Golden, CO 80401, USA
| | - Shi-You Ding
- Biosciences Center, National Renewable Energy Laboratory, Golden, CO 80401, USA
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66
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Chen X, Shekiro J, Franden MA, Wang W, Zhang M, Kuhn E, Johnson DK, Tucker MP. The impacts of deacetylation prior to dilute acid pretreatment on the bioethanol process. BIOTECHNOLOGY FOR BIOFUELS 2012; 5:8. [PMID: 22369467 DOI: 10.1186/1754-6834-1185-1188] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Received: 01/06/2012] [Accepted: 02/27/2012] [Indexed: 05/28/2023]
Abstract
BACKGROUND 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. RESULTS 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. CONCLUSIONS 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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Affiliation(s)
- Xiaowen Chen
- National Bioenergy Center, National Renewable Energy Lab, 1617 Cole Blvd, Golden, CO 80127, USA.
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Chen X, Shekiro J, Franden MA, Wang W, Zhang M, Kuhn E, Johnson DK, Tucker MP. The impacts of deacetylation prior to dilute acid pretreatment on the bioethanol process. BIOTECHNOLOGY FOR BIOFUELS 2012; 5:8. [PMID: 22369467 PMCID: PMC3309953 DOI: 10.1186/1754-6834-5-8] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/06/2012] [Accepted: 02/27/2012] [Indexed: 05/02/2023]
Abstract
BACKGROUND 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. RESULTS 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. CONCLUSIONS 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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Affiliation(s)
- Xiaowen Chen
- National Bioenergy Center, National Renewable Energy Lab, 1617 Cole Blvd, Golden, CO 80127, USA
| | - Joseph Shekiro
- National Bioenergy Center, National Renewable Energy Lab, 1617 Cole Blvd, Golden, CO 80127, USA
| | - Mary Ann Franden
- National Bioenergy Center, National Renewable Energy Lab, 1617 Cole Blvd, Golden, CO 80127, USA
| | - Wei Wang
- Biosciences Center, National Renewable Energy Lab, 1617 Cole Blvd, Golden, CO 80127, USA
| | - Min Zhang
- National Bioenergy Center, National Renewable Energy Lab, 1617 Cole Blvd, Golden, CO 80127, USA
| | - Erik Kuhn
- National Bioenergy Center, National Renewable Energy Lab, 1617 Cole Blvd, Golden, CO 80127, USA
| | - David K Johnson
- Biosciences Center, National Renewable Energy Lab, 1617 Cole Blvd, Golden, CO 80127, USA
| | - Melvin P Tucker
- National Bioenergy Center, National Renewable Energy Lab, 1617 Cole Blvd, Golden, CO 80127, USA
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Abstract
Conversion of plant cell walls to ethanol constitutes second generation bioethanol production. The process consists of several steps: biomass selection/genetic modification, physiochemical pretreatment, enzymatic saccharification, fermentation and separation. Ultimately, it is desirable to combine as many of the biochemical steps as possible in a single organism to achieve CBP (consolidated bioprocessing). A commercially ready CBP organism is currently unreported. Production of second generation bioethanol is hindered by economics, particularly in the cost of pretreatment (including waste management and solvent recovery), the cost of saccharification enzymes (particularly exocellulases and endocellulases displaying kcat ~1 s−1 on crystalline cellulose), and the inefficiency of co-fermentation of 5- and 6-carbon monosaccharides (owing in part to redox cofactor imbalances in Saccharomyces cerevisiae).
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Laurens LML, Dempster TA, Jones HDT, Wolfrum EJ, Van Wychen S, McAllister JSP, Rencenberger M, Parchert KJ, Gloe LM. Algal biomass constituent analysis: method uncertainties and investigation of the underlying measuring chemistries. Anal Chem 2012; 84:1879-87. [PMID: 22242663 DOI: 10.1021/ac202668c] [Citation(s) in RCA: 96] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Algal biomass compositional analysis data form the basis of a large number of techno-economic process analysis models that are used to investigate and compare different processes in algal biofuels production. However, the analytical methods used to generate these data are far from standardized. This work investigated the applicability of common methods for rapid chemical analysis of biomass samples with respect to accuracy and precision. This study measured lipids, protein, carbohydrates, ash, and moisture of a single algal biomass sample at 3 institutions by 8 independent researchers over 12 separate workdays. Results show statistically significant differences in the results from a given analytical method among laboratories but not between analysts at individual laboratories, suggesting consistent training is a critical issue for empirical analytical methods. Significantly different results from multiple lipid and protein measurements were found to be due to different measurement chemistries. We identified a set of compositional analysis procedures that are in best agreement with data obtained by more advanced analytical procedures. The methods described here and used for the round robin experiment do not require specialized instrumentation, and with detailed analytical documentation, the differences between laboratories can be markedly reduced.
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Affiliation(s)
- Lieve M L Laurens
- National Bioenergy Center, National Renewable Energy Laboratory, 1617 Cole Boulevard, Golden, Colorado 80401, USA.
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70
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Chen X, Shekiro J, Elander R, Tucker M. Improved Xylan Hydrolysis of Corn Stover by Deacetylation with High Solids Dilute Acid Pretreatment. Ind Eng Chem Res 2011. [DOI: 10.1021/ie201493g] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Xiaowen Chen
- National Bioenergy Center, National Renewable Energy Laboratory, 1617 Cole Boulevard, Golden, Colorado 80401, United States
| | - Joseph Shekiro
- National Bioenergy Center, National Renewable Energy Laboratory, 1617 Cole Boulevard, Golden, Colorado 80401, United States
| | - Rick Elander
- National Bioenergy Center, National Renewable Energy Laboratory, 1617 Cole Boulevard, Golden, Colorado 80401, United States
| | - Melvin Tucker
- National Bioenergy Center, National Renewable Energy Laboratory, 1617 Cole Boulevard, Golden, Colorado 80401, United States
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71
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Masarin F, Gurpilhares DB, Baffa DCF, Barbosa MHP, Carvalho W, Ferraz A, Milagres AMF. Chemical composition and enzymatic digestibility of sugarcane clones selected for varied lignin content. BIOTECHNOLOGY FOR BIOFUELS 2011; 4:55. [PMID: 22145819 PMCID: PMC3267660 DOI: 10.1186/1754-6834-4-55] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/16/2011] [Accepted: 12/06/2011] [Indexed: 05/03/2023]
Abstract
BACKGROUND The recalcitrance of lignocellulosic materials is a major limitation for their conversion into fermentable sugars. Lignin depletion in new cultivars or transgenic plants has been identified as a way to diminish this recalcitrance. In this study, we assessed the success of a sugarcane breeding program in selecting sugarcane plants with low lignin content, and report the chemical composition and agronomic characteristics of eleven experimental hybrids and two reference samples. The enzymatic digestion of untreated and chemically delignified samples was evaluated to advance the performance of the sugarcane residue (bagasse) in cellulosic-ethanol production processes. RESULTS The ranges for the percentages of glucan, hemicellulose, lignin, and extractive (based on oven-dry biomass) of the experimental hybrids and reference samples were 38% to 43%, 25% to 32%, 17% to 24%, and 1.6% to 7.5%, respectively. The samples with the smallest amounts of lignin did not produce the largest amounts of total polysaccharides. Instead, a variable increase in the mass of a number of components, including extractives, seemed to compensate for the reduction in lignin content. Hydroxycinnamic acids accounted for a significant part of the aromatic compounds in the samples, with p-coumaric acid predominating, whereas ferulic acid was present only in low amounts. Hydroxycinnamic acids with ester linkage to the hemicelluloses varied from 2.3% to 3.6%. The percentage of total hydroxycinnamic acids (including the fraction linked to lignin through ether linkages) varied from 5.0% to 9.2%, and correlated to some extent with the lignin content. These clones released up to 31% of glucose after 72 hours of digestion with commercial cellulases, whereas chemically delignified samples led to cellulose conversion values of more than 80%. However, plants with lower lignin content required less delignification to reach higher efficiencies of cellulose conversion during the enzymatic treatment. CONCLUSION Some of the experimental sugarcane hybrids did have the combined characteristics of high biomass and high sucrose production with low lignin content. Conversion of glucan to glucose by commercial cellulases was increased in the samples with low lignin content. Chemical delignification further increased the cellulose conversion to values of more than 80%. Thus, plants with lower lignin content required less delignification to reach higher efficiencies of cellulose conversion during the enzymatic treatment.
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Affiliation(s)
- Fernando Masarin
- Departamento de Biotecnologia, Escola de Engenharia de Lorena, Universidade de São Paulo, CP 116, 12602-810 Lorena, SP, Brasil
| | - Daniela B Gurpilhares
- Departamento de Biotecnologia, Escola de Engenharia de Lorena, Universidade de São Paulo, CP 116, 12602-810 Lorena, SP, Brasil
| | - David CF Baffa
- Departamento de Fitotecnia, Universidade Federal de Viçosa, Viçosa, MG, Brazil
| | - Márcio HP Barbosa
- Departamento de Fitotecnia, Universidade Federal de Viçosa, Viçosa, MG, Brazil
| | - Walter Carvalho
- Departamento de Biotecnologia, Escola de Engenharia de Lorena, Universidade de São Paulo, CP 116, 12602-810 Lorena, SP, Brasil
| | - André Ferraz
- Departamento de Biotecnologia, Escola de Engenharia de Lorena, Universidade de São Paulo, CP 116, 12602-810 Lorena, SP, Brasil
| | - Adriane MF Milagres
- Departamento de Biotecnologia, Escola de Engenharia de Lorena, Universidade de São Paulo, CP 116, 12602-810 Lorena, SP, Brasil
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Rezende CA, de Lima MA, Maziero P, deAzevedo ER, Garcia W, Polikarpov I. Chemical and morphological characterization of sugarcane bagasse submitted to a delignification process for enhanced enzymatic digestibility. BIOTECHNOLOGY FOR BIOFUELS 2011; 4:54. [PMID: 22122978 PMCID: PMC3377919 DOI: 10.1186/1754-6834-4-54] [Citation(s) in RCA: 102] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/01/2011] [Accepted: 11/28/2011] [Indexed: 05/03/2023]
Abstract
BACKGROUND In recent years, biorefining of lignocellulosic biomass to produce multi-products such as ethanol and other biomaterials has become a dynamic research area. Pretreatment technologies that fractionate sugarcane bagasse are essential for the successful use of this feedstock in ethanol production. In this paper, we investigate modifications in the morphology and chemical composition of sugarcane bagasse submitted to a two-step treatment, using diluted acid followed by a delignification process with increasing sodium hydroxide concentrations. Detailed chemical and morphological characterization of the samples after each pretreatment condition, studied by high performance liquid chromatography, solid-state nuclear magnetic resonance, diffuse reflectance Fourier transformed infrared spectroscopy and scanning electron microscopy, is reported, together with sample crystallinity and enzymatic digestibility. RESULTS Chemical composition analysis performed on samples obtained after different pretreatment conditions showed that up to 96% and 85% of hemicellulose and lignin fractions, respectively, were removed by this two-step method when sodium hydroxide concentrations of 1% (m/v) or higher were used. The efficient lignin removal resulted in an enhanced hydrolysis yield reaching values around 100%. Considering the cellulose loss due to the pretreatment (maximum of 30%, depending on the process), the total cellulose conversion increases significantly from 22.0% (value for the untreated bagasse) to 72.4%. The delignification process, with consequent increase in the cellulose to lignin ratio, is also clearly observed by nuclear magnetic resonance and diffuse reflectance Fourier transformed infrared spectroscopy experiments. We also demonstrated that the morphological changes contributing to this remarkable improvement occur as a consequence of lignin removal from the sample. Bagasse unstructuring is favored by the loss of cohesion between neighboring cell walls, as well as by changes in the inner cell wall structure, such as damaging, hole formation and loss of mechanical resistance, facilitating liquid and enzyme access to crystalline cellulose. CONCLUSIONS The results presented herewith show the efficiency of the proposed method for improving the enzymatic digestibility of sugarcane bagasse and provide understanding of the pretreatment action mechanism. Combining the different techniques applied in this work warranted thorough information about the undergoing morphological and chemical changes and was an efficient approach to understand the morphological effects resulting from sample delignification and its influence on the enhanced hydrolysis results.
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Affiliation(s)
- Camila Alves Rezende
- Instituto de Física de São Carlos, Universidade de São Paulo, Caixa Postal 369, CEP 13560-970, São Carlos, SP, Brazil
| | - Marisa Aparecida de Lima
- Instituto de Física de São Carlos, Universidade de São Paulo, Caixa Postal 369, CEP 13560-970, São Carlos, SP, Brazil
| | - Priscila Maziero
- Escola de Engenharia de Lorena, Universidade de São Paulo, CEP 12602-810, Lorena, SP, Brazil
| | - Eduardo Ribeiro deAzevedo
- Instituto de Física de São Carlos, Universidade de São Paulo, Caixa Postal 369, CEP 13560-970, São Carlos, SP, Brazil
| | - Wanius Garcia
- Universidade Federal do ABC, CEP 009210-170, Santo André, SP, Brazil
| | - Igor Polikarpov
- Instituto de Física de São Carlos, Universidade de São Paulo, Caixa Postal 369, CEP 13560-970, São Carlos, SP, Brazil
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McMillan JD, Jennings EW, Mohagheghi A, Zuccarello M. Comparative performance of precommercial cellulases hydrolyzing pretreated corn stover. BIOTECHNOLOGY FOR BIOFUELS 2011; 4:29. [PMID: 21899748 PMCID: PMC3200994 DOI: 10.1186/1754-6834-4-29] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/26/2011] [Accepted: 09/07/2011] [Indexed: 05/02/2023]
Abstract
BACKGROUND Cellulases and related hydrolytic enzymes represent a key cost factor for biochemical conversion of cellulosic biomass feedstocks to sugars for biofuels and chemicals production. The US Department of Energy (DOE) is cost sharing projects to decrease the cost of enzymes for biomass saccharification. The performance of benchmark cellulase preparations produced by Danisco, DSM, Novozymes and Verenium to convert pretreated corn stover (PCS) cellulose to glucose was evaluated under common experimental conditions and is reported here in a non-attributed manner. RESULTS Two hydrolysis modes were examined, enzymatic hydrolysis (EH) of PCS whole slurry or washed PCS solids at pH 5 and 50°C, and simultaneous saccharification and fermentation (SSF) of washed PCS solids at pH 5 and 38°C. Enzymes were dosed on a total protein mass basis, with protein quantified using both the bicinchoninic acid (BCA) assay and the Bradford assay. Substantial differences were observed in absolute cellulose to glucose conversion performance levels under the conditions tested. Higher cellulose conversion yields were obtained using washed solids compared to whole slurry, and estimated enzyme protein dosages required to achieve a particular cellulose conversion to glucose yield were extremely dependent on the protein assay used. All four enzyme systems achieved glucose yields of 90% of theoretical or higher in SSF mode. Glucose yields were reduced in EH mode, with all enzymes achieving glucose yields of at least 85% of theoretical on washed PCS solids and 75% in PCS whole slurry. One of the enzyme systems ('enzyme B') exhibited the best overall performance. However in attaining high conversion yields at lower total enzyme protein loadings, the relative and rank ordered performance of the enzyme systems varied significantly depending upon which hydrolysis mode and protein assay were used as the basis for comparison. CONCLUSIONS This study provides extensive information about the performance of four precommercial cellulase preparations. Though test conditions were not necessarily optimal for some of the enzymes, all were able to effectively saccharify PCS cellulose. Large differences in the estimated enzyme dosage requirements depending on the assay used to measure protein concentration highlight the need for better consensus methods to quantify enzyme protein.
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Affiliation(s)
- James D McMillan
- National Bioenergy Center, National Renewable Energy Laboratory, Golden, CO, USA
| | - Edward W Jennings
- National Bioenergy Center, National Renewable Energy Laboratory, Golden, CO, USA
| | - Ali Mohagheghi
- National Bioenergy Center, National Renewable Energy Laboratory, Golden, CO, USA
| | - Mildred Zuccarello
- National Bioenergy Center, National Renewable Energy Laboratory, Golden, CO, USA
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Godin B, Agneessens R, Gerin PA, Delcarte J. Composition of structural carbohydrates in biomass: precision of a liquid chromatography method using a neutral detergent extraction and a charged aerosol detector. Talanta 2011; 85:2014-26. [PMID: 21872053 DOI: 10.1016/j.talanta.2011.07.044] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2011] [Revised: 07/04/2011] [Accepted: 07/09/2011] [Indexed: 11/26/2022]
Abstract
We adapted and optimized a method to quantify the cellulose, hemicellulose, xylan, arabinan, mannan, galactan contents in lignocellulosic biomass. This method is based on a neutral detergent extraction (NDE) of the interfering biomass components, followed by a sulfuric acid hydrolysis (SAH) of the structural polysaccharides, and a liquid chromatography with charged aerosol detection (LC-CAD) to analyze the released monosaccharides. The first step of this NDE-SAH-LC-CAD method aims at removing all compounds that interfere with the subsequent sulphuric acid hydrolysis or with the subsequent chromatographic quantification of the cellulosic and hemicellulosic monosaccharides. This step includes starch hydrolysis with an analytical thermostable α-amylase followed by an extraction of soluble compounds by a Van Soest neutral detergent solution (NDE). The aim of this paper was to assess the precision of this method when choosing fiber sorghum (Sorghum bicolor (L.) Moench), tall fescue (Festuca arundinacea Schreb.) and fiber hemp (Cannabis sativa L.) as representative lignocellulosic biomass. The cellulose content of fiber sorghum, tall fescue and fiber hemp determined by the NDE-SAH-LC-CAD method were 28.7 ± 1.0, 29.7 ± 1.0 and 43.6 ± 1.2g/100g dry matter, respectively, and their hemicellulose content were 18.6 ± 0.5, 16.5 ± 0.5 and 14.5 ± 0.2g/100g dry matter, respectively. Cellulose, mannan and galactan contents were higher in fiber hemp (dicotyledon) as compared to tall fescue and fiber sorghum (monocotyledons). The xylan, arabinan and total hemicellulose contents were higher in tall fescue and fiber sorghum as compared to fiber hemp. The precision of the NDE-SAH-LC-CAD method was better for polysaccharide concentration levels above 1g/100g dry matter. Galactan analysis offered a lower precision, due to a lower CAD response intensity to galactose as compared to the other monosaccharides. The dispersions of the results (expanded uncertainty) of the NDE-SAH-LC-CAD method were smaller as compared to the Van Soest (VS) method. In addition, the NDE-SAH-LC-CAD method was able to provide additional information on the composition of the hemicellulose (xylan, arabinan, mannan and galactan content) that is not provided by the Van Soest method. The NDE-SAH-LC-CAD method offers also the advantage of a better specificity for hemicellulose and cellulose, as compared to the NREL and Uppsala methods.
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Affiliation(s)
- Bruno Godin
- Walloon Agricultural Research Center - CRA-W, Valorisation of Agricultural Products Departmen, Chaussée de Namur, 146. B-5030 Gembloux, Belgium.
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Sluiter JB, Ruiz RO, Scarlata CJ, Sluiter AD, Templeton DW. Compositional analysis of lignocellulosic feedstocks. 1. Review and description of methods. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2010; 58:9043-53. [PMID: 20669951 PMCID: PMC2923870 DOI: 10.1021/jf1008023] [Citation(s) in RCA: 352] [Impact Index Per Article: 25.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
As interest in lignocellulosic biomass feedstocks for conversion into transportation fuels grows, the summative compositional analysis of biomass, or plant-derived material, becomes ever more important. The sulfuric acid hydrolysis of biomass has been used to measure lignin and structural carbohydrate content for more than 100 years. Researchers have applied these methods to measure the lignin and structural carbohydrate contents of woody materials, estimate the nutritional value of animal feed, analyze the dietary fiber content of human food, compare potential biofuels feedstocks, and measure the efficiency of biomass-to-biofuels processes. The purpose of this paper is to review the history and lineage of biomass compositional analysis methods based on a sulfuric acid hydrolysis. These methods have become the de facto procedure for biomass compositional analysis. The paper traces changes to the biomass compositional analysis methods through time to the biomass methods currently used at the National Renewable Energy Laboratory (NREL). The current suite of laboratory analytical procedures (LAPs) offered by NREL is described, including an overview of the procedures and methodologies and some common pitfalls. Suggestions are made for continuing improvement to the suite of analyses.
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Affiliation(s)
| | | | | | | | - David W. Templeton
- Corresponding author [e-mail ; phone (303) 384-7764; fax (303) 384-6877]
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