51
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Pönni R, Galvis L, Vuorinen T. Changes in accessibility of cellulose during kraft pulping of wood in deuterium oxide. Carbohydr Polym 2014; 101:792-7. [DOI: 10.1016/j.carbpol.2013.10.001] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2013] [Revised: 09/30/2013] [Accepted: 10/02/2013] [Indexed: 11/16/2022]
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52
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Eibinger M, Bubner P, Ganner T, Plank H, Nidetzky B. Surface structural dynamics of enzymatic cellulose degradation, revealed by combined kinetic and atomic force microscopy studies. FEBS J 2013; 281:275-90. [DOI: 10.1111/febs.12594] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2013] [Revised: 10/18/2013] [Accepted: 10/21/2013] [Indexed: 02/01/2023]
Affiliation(s)
- Manuel Eibinger
- Institute of Biotechnology and Biochemical Engineering; Graz University of Technology; Austria
| | - Patricia Bubner
- Institute of Biotechnology and Biochemical Engineering; Graz University of Technology; Austria
| | - Thomas Ganner
- Institute for Electron Microscopy and Fine Structure Research; Graz University of Technology; Austria
- Center for Electron Microscopy; Graz University of Technology; Austria
| | - Harald Plank
- Institute for Electron Microscopy and Fine Structure Research; Graz University of Technology; Austria
- Center for Electron Microscopy; Graz University of Technology; Austria
| | - Bernd Nidetzky
- Institute of Biotechnology and Biochemical Engineering; Graz University of Technology; Austria
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53
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Wang J, Quirk A, Lipkowski J, Dutcher JR, Clarke AJ. Direct in situ observation of synergism between cellulolytic enzymes during the biodegradation of crystalline cellulose fibers. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2013; 29:14997-5005. [PMID: 24195649 DOI: 10.1021/la403401c] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
High-resolution atomic force microscopy (AFM) was used to image the real-time in situ degradation of crystalline by three types of T. reesei cellulolytic enzymes-TrCel6A, TrCel7A, and TrCel7B-and their mixtures. TrCel6A and TrCel7A are exo-acting cellobiohydrolases processing cellulose fibers from the nonreducing and reducing ends, respectively. TrCel7B is an endoglucanase that hydrolyzes amorphous cellulose within fibers. When acting alone on native cellulose fibers, each of the three enzymes is incapable of significant degradation. However, mixtures of two enzymes exhibited synergistic effects. The degradation effects of this synergism depended on the order in which the enzymes were added. Faster hydrolysis rates were observed when TrCel7A (exo) was added to fibers pretreated first with TrCel7B (endo) than when adding the enzymes in the opposite order. Endo-acting TrCel7B removed amorphous cellulose, softened and swelled the fibers, and exposed single microfibrils, facilitating the attack by the exo-acting enzymes. AFM images revealed that exo-acting enzymes processed the TrCel7B-pretreated fibers preferentially from one specific end (reducing or nonreducing). The most efficient (almost 100%) hydrolysis was observed with the mixture of the three enzymes. In this mixture, TrCel7B softened the fiber and TrCel6A and TrCel7A were directly observed to process it from the two opposing ends. This study provides high-resolution direct visualization of the nature of the synergistic relation between T. reesei exo- and endo-acting enzymes digesting native crystalline cellulose.
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Affiliation(s)
- Jingpeng Wang
- Department of Chemistry, ‡Department of Physics, and §Department of Molecular and Cellular Biology, University of Guelph , Guelph, Ontario N1G 2W1, Canada
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54
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Kamat RK, Ma W, Yang Y, Zhang Y, Wang C, Kumar CV, Lin Y. Adsorption and hydrolytic activity of the polycatalytic cellulase nanocomplex on cellulose. ACS APPLIED MATERIALS & INTERFACES 2013; 5:8486-8494. [PMID: 23968137 DOI: 10.1021/am401916k] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
The formation of polycatalytic enzyme complexes may enhance the effectiveness of enzymes due to improved substrate interaction and synergistic actions of multiple enzymes in proximity. Much effort has been made to develop highly efficient polycatalytic cellulase complexes by immobilizing cellulases on low-cost polymer or nanoparticle scaffolds, aiming at their potential applications in biomass conversion to fuels. However, some key cellulases carry out the hydrolytic reaction on crystalline cellulose in a directional, processive manner. A large, artificial polycatalytic complex is unlikely to undergo a highly coordinated motion to slide on the cellulose surface as a whole unit. The mechanism underlying the activity enhancements observed in some artificial cellulase complexes and the limit of this approach remain elusive. Herein, we report the synthesis of polycatalytic cellulase complexes bound to colloidal polymer nanoparticles with a magnetic core and describe their unique adsorption, hydrolytic activities, and motions on cellulose. The polycatalytic clusters of cellulases on colloidal polymers show an increased rate of hydrolytic reactions on cellulose, but this was observed mainly at relatively low cellulase-to-cellulose ratios. Enhanced efficiency is mainly attributed to increased local concentrations of cellulases on the scaffolds and their polyvalent interactions with cellulose. However, once bound, the polycatalytic complexes can only carry out reactions locally and are not capable of relocating to new sites rapidly due to their lack of long-range surface mobility and their extremely tight binding. The development of highly optimized polycatalytic complexes may arise by developing novel nanoscaffolds that induce concerted motion of the complex as a whole.
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Affiliation(s)
- Ranjan K Kamat
- Polymer Program, Institute of Material Science, §Department of Chemistry, and ∥Department of Molecular and Cellular Biology, University of Connecticut , Storrs, Connecticut 06269, United States
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55
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Wang TY, Huang CJ, Chen HL, Ho PC, Ke HM, Cho HY, Ruan SK, Hung KY, Wang IL, Cai YW, Sung HM, Li WH, Shih MC. Systematic screening of glycosylation- and trafficking-associated gene knockouts in Saccharomyces cerevisiae identifies mutants with improved heterologous exocellulase activity and host secretion. BMC Biotechnol 2013; 13:71. [PMID: 24004614 PMCID: PMC3766678 DOI: 10.1186/1472-6750-13-71] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2012] [Accepted: 08/29/2013] [Indexed: 11/28/2022] Open
Abstract
Background As a strong fermentator, Saccharomyces cerevisiae has the potential to be an excellent host for ethanol production by consolidated bioprocessing. For this purpose, it is necessary to transform cellulose genes into the yeast genome because it contains no cellulose genes. However, heterologous protein expression in S. cerevisiae often suffers from hyper-glycosylation and/or poor secretion. Thus, there is a need to genetically engineer the yeast to reduce its glycosylation strength and to increase its secretion ability. Results Saccharomyces cerevisiae gene-knockout strains were screened for improved extracellular activity of a recombinant exocellulase (PCX) from the cellulose digesting fungus Phanerochaete chrysosporium. Knockout mutants of 47 glycosylation-related genes and 10 protein-trafficking-related genes were transformed with a PCX expression construct and screened for extracellular cellulase activity. Twelve of the screened mutants were found to have a more than 2-fold increase in extracellular PCX activity in comparison with the wild type. The extracellular PCX activities in the glycosylation-related mnn10 and pmt5 null mutants were, respectively, 6 and 4 times higher than that of the wild type; and the extracellular PCX activities in 9 protein-trafficking-related mutants, especially in the chc1, clc1 and vps21 null mutants, were at least 1.5 times higher than the parental strains. Site-directed mutagenesis studies further revealed that the degree of N-glycosylation also plays an important role in heterologous cellulase activity in S. cerevisiae. Conclusions Systematic screening of knockout mutants of glycosylation- and protein trafficking-associated genes in S. cerevisiae revealed that: (1) blocking Golgi-to-endosome transport may force S. cerevisiae to export cellulases; and (2) both over- and under-glycosylation may alter the enzyme activity of cellulases. This systematic gene-knockout screening approach may serve as a convenient means for increasing the extracellular activities of recombinant proteins expressed in S. cerevisiae.
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Affiliation(s)
- Tzi-Yuan Wang
- Biodiversity Research Center, Academia Sinica, Taipei 115, Taiwan.
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56
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Shang BZ, Chang R, Chu JW. Systems-level modeling with molecular resolution elucidates the rate-limiting mechanisms of cellulose decomposition by cellobiohydrolases. J Biol Chem 2013; 288:29081-9. [PMID: 23950182 DOI: 10.1074/jbc.m113.497412] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Interprotein and enzyme-substrate couplings in interfacial biocatalysis induce spatial correlations beyond the capabilities of classical mass-action principles in modeling reaction kinetics. To understand the impact of spatial constraints on enzyme kinetics, we developed a computational scheme to simulate the reaction network of enzymes with the structures of individual proteins and substrate molecules explicitly resolved in the three-dimensional space. This methodology was applied to elucidate the rate-limiting mechanisms of crystalline cellulose decomposition by cellobiohydrolases. We illustrate that the primary bottlenecks are slow complexation of glucan chains into the enzyme active site and excessive enzyme jamming along the crowded substrate. Jamming could be alleviated by increasing the decomplexation rate constant but at the expense of reduced processivity. We demonstrate that enhancing the apparent reaction rate required a subtle balance between accelerating the complexation driving force and simultaneously avoiding enzyme jamming. Via a spatiotemporal systems analysis, we developed a unified mechanistic framework that delineates the experimental conditions under which different sets of rate-limiting behaviors emerge. We found that optimization of the complexation-exchange kinetics is critical for overcoming the barriers imposed by interfacial confinement and accelerating the apparent rate of enzymatic cellulose decomposition.
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Affiliation(s)
- Barry Z Shang
- From the Department of Chemical and Biomolecular Engineering, University of California, Berkeley, California 94720
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57
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Accessibility of cellulose: Structural changes and their reversibility in aqueous media. Carbohydr Polym 2013; 93:424-9. [DOI: 10.1016/j.carbpol.2012.12.025] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2012] [Revised: 12/10/2012] [Accepted: 12/16/2012] [Indexed: 11/19/2022]
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58
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Bubner P, Plank H, Nidetzky B. Visualizing cellulase activity. Biotechnol Bioeng 2013; 110:1529-49. [DOI: 10.1002/bit.24884] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2012] [Revised: 01/08/2013] [Accepted: 02/22/2013] [Indexed: 11/08/2022]
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59
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Pei Y, Yang J, Liu P, Xu M, Zhang X, Zhang L. Fabrication, properties and bioapplications of cellulose/collagen hydrolysate composite films. Carbohydr Polym 2013; 92:1752-60. [DOI: 10.1016/j.carbpol.2012.11.029] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2012] [Revised: 09/14/2012] [Accepted: 11/08/2012] [Indexed: 10/27/2022]
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60
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Penttilä PA, Várnai A, Pere J, Tammelin T, Salmén L, Siika-aho M, Viikari L, Serimaa R. Xylan as limiting factor in enzymatic hydrolysis of nanocellulose. BIORESOURCE TECHNOLOGY 2013; 129:135-41. [PMID: 23238342 DOI: 10.1016/j.biortech.2012.11.017] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/31/2012] [Revised: 11/01/2012] [Accepted: 11/02/2012] [Indexed: 05/10/2023]
Abstract
The role of xylan as a limiting factor in the enzymatic hydrolysis of cellulose was studied by hydrolysing nanocellulose samples prepared by mechanical fibrillation of birch pulp with varying xylan content. Analyzing the nanocelluloses and their hydrolysis residues with dynamic FT-IR spectroscopy revealed that a certain fraction of xylan remained tightly attached to cellulose fibrils despite partial hydrolysis of xylan with xylanase prior to pulp fibrillation and that this fraction remained in the structure during the hydrolysis of nanocellulose with cellulase mixture as well. Thus, a loosely bound fraction of xylan was predicted to have been more likely removed by purified xylanase. The presence of loosely bound xylan seemed to limit the hydrolysis of crystalline cellulose, indicated by an increase in cellulose crystallinity and by preserved crystal width measured with wide-angle X-ray scattering. Removing loosely bound xylan led to a proportional hydrolysis of xylan and cellulose with the cellulase mixture.
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Affiliation(s)
- Paavo A Penttilä
- University of Helsinki, Department of Physics, P.O. Box 64, FI-00014 Helsinki, Finland.
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61
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Thomas LH, Forsyth VT, Šturcová A, Kennedy CJ, May RP, Altaner CM, Apperley DC, Wess TJ, Jarvis MC. Structure of cellulose microfibrils in primary cell walls from collenchyma. PLANT PHYSIOLOGY 2013; 161:465-76. [PMID: 23175754 PMCID: PMC3532275 DOI: 10.1104/pp.112.206359] [Citation(s) in RCA: 172] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/29/2012] [Accepted: 11/13/2012] [Indexed: 05/17/2023]
Abstract
In the primary walls of growing plant cells, the glucose polymer cellulose is assembled into long microfibrils a few nanometers in diameter. The rigidity and orientation of these microfibrils control cell expansion; therefore, cellulose synthesis is a key factor in the growth and morphogenesis of plants. Celery (Apium graveolens) collenchyma is a useful model system for the study of primary wall microfibril structure because its microfibrils are oriented with unusual uniformity, facilitating spectroscopic and diffraction experiments. Using a combination of x-ray and neutron scattering methods with vibrational and nuclear magnetic resonance spectroscopy, we show that celery collenchyma microfibrils were 2.9 to 3.0 nm in mean diameter, with a most probable structure containing 24 chains in cross section, arranged in eight hydrogen-bonded sheets of three chains, with extensive disorder in lateral packing, conformation, and hydrogen bonding. A similar 18-chain structure, and 24-chain structures of different shape, fitted the data less well. Conformational disorder was largely restricted to the surface chains, but disorder in chain packing was not. That is, in position and orientation, the surface chains conformed to the disordered lattice constituting the core of each microfibril. There was evidence that adjacent microfibrils were noncovalently aggregated together over part of their length, suggesting that the need to disrupt these aggregates might be a constraining factor in growth and in the hydrolysis of cellulose for biofuel production.
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62
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Ding SY, Liu YS, Zeng Y, Himmel ME, Baker JO, Bayer EA. How Does Plant Cell Wall Nanoscale Architecture Correlate with Enzymatic Digestibility? Science 2012. [PMID: 23180856 DOI: 10.1126/science.1227491] [Citation(s) in RCA: 554] [Impact Index Per Article: 46.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Affiliation(s)
- Shi-You Ding
- Biosciences Center, National Renewable Energy Laboratory, Golden, CO 80401, USA.
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63
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Ganner T, Bubner P, Eibinger M, Mayrhofer C, Plank H, Nidetzky B. Dissecting and reconstructing synergism: in situ visualization of cooperativity among cellulases. J Biol Chem 2012; 287:43215-22. [PMID: 23118223 PMCID: PMC3527909 DOI: 10.1074/jbc.m112.419952] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Cellulose is the most abundant biopolymer and a major reservoir of fixed carbon on earth. Comprehension of the elusive mechanism of its enzymatic degradation represents a fundamental problem at the interface of biology, biotechnology, and materials science. The interdependence of cellulose disintegration and hydrolysis and the synergistic interplay among cellulases is yet poorly understood. Here we report evidence from in situ atomic force microscopy (AFM) that delineates degradation of a polymorphic cellulose substrate as a dynamic cycle of alternating exposure and removal of crystalline fibers. Direct observation shows that chain-end-cleaving cellobiohydrolases (CBH I, CBH II) and an internally chain-cleaving endoglucanase (EG), the major components of cellulase systems, take on distinct roles: EG and CBH II make the cellulose surface accessible for CBH I by removing amorphous-unordered substrate areas, thus exposing otherwise embedded crystalline-ordered nanofibrils of the cellulose. Subsequently, these fibrils are degraded efficiently by CBH I, thereby uncovering new amorphous areas. Without prior action of EG and CBH II, CBH I was poorly active on the cellulosic substrate. This leads to the conclusion that synergism among cellulases is morphology-dependent and governed by the cooperativity between enzymes degrading amorphous regions and those targeting primarily crystalline regions. The surface-disrupting activity of cellulases therefore strongly depends on mesoscopic structural features of the substrate: size and packing of crystalline fibers are key determinants of the overall efficiency of cellulose degradation.
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Affiliation(s)
- Thomas Ganner
- Institute for Electron Microscopy and Fine Structure Research, Graz University of Technology, Steyrergasse 17, A-8010 Graz, Austria
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64
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Heterologous expression of cellobiohydrolase II (Cel6A) in maize endosperm. Transgenic Res 2012; 22:477-88. [PMID: 23080294 DOI: 10.1007/s11248-012-9659-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2012] [Accepted: 09/21/2012] [Indexed: 10/27/2022]
Abstract
The technology of converting lignocellulose to biofuels has advanced swiftly over the past few years, and enzymes are a significant constituent of this technology. In this regard, cost effective production of cellulases has been the focus of research for many years. One approach to reach cost targets of these enzymes involves the use of plants as bio-factories. The application of this technology to plant biomass conversion for biofuels and biobased products has the potential for significantly lowering the cost of these products due to lower enzyme production costs. Cel6A, one of the two cellobiohydrolases (CBH II) produced by Hypocrea jecorina, is an exoglucanase that cleaves primarily cellobiose units from the non-reducing end of cellulose microfibrils. In this work we describe the expression of Cel6A in maize endosperm as part of the process to lower the cost of this dominant enzyme for the bioconversion process. The enzyme is active on microcrystalline cellulose as exponential microbial growth was observed in the mixture of cellulose, cellulases, yeast and Cel6A, Cel7A (endoglucanase), and Cel5A (cellobiohydrolase I) expressed in maize seeds. We quantify the amount accumulated and the activity of the enzyme. Cel6A expressed in maize endosperm was purified to homogeneity and verified using peptide mass finger printing.
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65
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Ruel K, Nishiyama Y, Joseleau JP. Crystalline and amorphous cellulose in the secondary walls of Arabidopsis. PLANT SCIENCE : AN INTERNATIONAL JOURNAL OF EXPERIMENTAL PLANT BIOLOGY 2012; 193-194:48-61. [PMID: 22794918 DOI: 10.1016/j.plantsci.2012.05.008] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/16/2011] [Revised: 05/09/2012] [Accepted: 05/11/2012] [Indexed: 06/01/2023]
Abstract
In the cell walls of higher plants, cellulose chains are present in crystalline microfibril, with an amorphous part at the surface, or present as amorphous material. To assess the distribution and relative occurrence of the two forms of cellulose in the inflorescence stem of Arabidopsis, we used two carbohydrate-binding modules, CBM3a and CBM28, specific for crystalline and amorphous cellulose, respectively, with immunogold detection in TEM. The binding of the two CBMs displayed specific patterns suggesting that the synthesis of cellulose leads to variable nanodomains of cellulose structures according to cell type. In developing cell walls, only CBM3a bound significantly to the incipient primary walls, indicating that at the onset of its deposition cellulose is in a crystalline structure. As the secondary wall develops, the labeling with both CBMs becomes more intense. The variation of the labeling pattern by CBM3a between transverse and longitudinal sections appeared related to microfibril orientation and differed between fibers and vessels. Although the two CBMs do not allow the description of the complete status of cellulose microstructures, they revealed the dynamics of the deposition of crystalline and amorphous forms of cellulose during wall formation and between cell types adapting cellulose microstructures to the cell function.
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Affiliation(s)
- Katia Ruel
- Centre de Recherches sur les Macromolécules Végétales (CERMAV-CNRS UPR 5301), BP 53 38041 Grenoble CEDEX 9, France
| | - Yoshiharu Nishiyama
- Centre de Recherches sur les Macromolécules Végétales (CERMAV-CNRS UPR 5301), BP 53 38041 Grenoble CEDEX 9, France
| | - Jean-Paul Joseleau
- Centre de Recherches sur les Macromolécules Végétales (CERMAV-CNRS UPR 5301), BP 53 38041 Grenoble CEDEX 9, France.
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66
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Glass DC, Moritsugu K, Cheng X, Smith JC. REACH Coarse-Grained Simulation of a Cellulose Fiber. Biomacromolecules 2012; 13:2634-44. [DOI: 10.1021/bm300460f] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Dennis C. Glass
- UT/ORNL
Center for
Molecular Biophysics, Oak Ridge National Laboratory, P.O. Box 2008 Oak Ridge, Tennessee 37831-6309,
United States
- Graduate School
of Genome Science and Technology, The University of Tennessee, Knoxville, Tennessee 37996, United States
| | - Kei Moritsugu
- Research Program for
Computational Science, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - Xiaolin Cheng
- UT/ORNL
Center for
Molecular Biophysics, Oak Ridge National Laboratory, P.O. Box 2008 Oak Ridge, Tennessee 37831-6309,
United States
- Department of Biochemistry
and Molecular and Cellular Biology, University of Tennessee, M407 Walters Life Sciences, 1414 Cumberland
Avenue, Knoxville, Tennessee 37996, United States
| | - Jeremy C. Smith
- UT/ORNL
Center for
Molecular Biophysics, Oak Ridge National Laboratory, P.O. Box 2008 Oak Ridge, Tennessee 37831-6309,
United States
- Department of Biochemistry
and Molecular and Cellular Biology, University of Tennessee, M407 Walters Life Sciences, 1414 Cumberland
Avenue, Knoxville, Tennessee 37996, United States
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67
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Zhang M, Wu SC, Zhou W, Xu B. Imaging and Measuring Single-Molecule Interaction between a Carbohydrate-Binding Module and Natural Plant Cell Wall Cellulose. J Phys Chem B 2012; 116:9949-56. [DOI: 10.1021/jp304686q] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Affiliation(s)
- Mengmeng Zhang
- Single Molecule Study Laboratory,
Faculty of Engineering and Nanoscale Science and Engineering Center, University of Georgia, Athens, Georgia 30602, United
States
| | - Sheng-Cheng Wu
- Complex Carbohydrate
Research
Center and Department of Cellular Biology, University of Georgia, Athens, Georgia 30602, United States
| | - Wen Zhou
- Department of Chemical Engineering, Michigan Tech University, Houghton, Michigan 49931,
United States
| | - Bingqian Xu
- Single Molecule Study Laboratory,
Faculty of Engineering and Nanoscale Science and Engineering Center, University of Georgia, Athens, Georgia 30602, United
States
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68
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Foston M, Ragauskas AJ. Biomass Characterization: Recent Progress in Understanding Biomass Recalcitrance. Ind Biotechnol (New Rochelle N Y) 2012. [DOI: 10.1089/ind.2012.0015] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Affiliation(s)
- Marcus Foston
- BioEnergy Science Center, School of Chemistry and Biochemistry, Institute of Paper Science and Technology, Georgia Institute of Technology, Atlanta, GA
| | - Arthur J. Ragauskas
- BioEnergy Science Center, School of Chemistry and Biochemistry, Institute of Paper Science and Technology, Georgia Institute of Technology, Atlanta, GA
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69
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Horn SJ, Vaaje-Kolstad G, Westereng B, Eijsink VGH. Novel enzymes for the degradation of cellulose. BIOTECHNOLOGY FOR BIOFUELS 2012; 5:45. [PMID: 22747961 PMCID: PMC3492096 DOI: 10.1186/1754-6834-5-45] [Citation(s) in RCA: 584] [Impact Index Per Article: 48.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/16/2012] [Accepted: 06/18/2012] [Indexed: 05/02/2023]
Abstract
The bulk terrestrial biomass resource in a future bio-economy will be lignocellulosic biomass, which is recalcitrant and challenging to process. Enzymatic conversion of polysaccharides in the lignocellulosic biomass will be a key technology in future biorefineries and this technology is currently the subject of intensive research. We describe recent developments in enzyme technology for conversion of cellulose, the most abundant, homogeneous and recalcitrant polysaccharide in lignocellulosic biomass. In particular, we focus on a recently discovered new type of enzymes currently classified as CBM33 and GH61 that catalyze oxidative cleavage of polysaccharides. These enzymes promote the efficiency of classical hydrolytic enzymes (cellulases) by acting on the surfaces of the insoluble substrate, where they introduce chain breaks in the polysaccharide chains, without the need of first "extracting" these chains from their crystalline matrix.
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Affiliation(s)
- Svein Jarle Horn
- Department of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences, P.O. Box 5003, Aas, Norway
| | - Gustav Vaaje-Kolstad
- Department of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences, P.O. Box 5003, Aas, Norway
| | - Bjørge Westereng
- Department of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences, P.O. Box 5003, Aas, Norway
| | - Vincent GH Eijsink
- Department of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences, P.O. Box 5003, Aas, Norway
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70
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Wang J, Quirk A, Lipkowski J, Dutcher JR, Hill C, Mark A, Clarke AJ. Real-time observation of the swelling and hydrolysis of a single crystalline cellulose fiber catalyzed by cellulase 7B from Trichoderma reesei. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2012; 28:9664-9672. [PMID: 22646051 DOI: 10.1021/la301030f] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
The biodegradation of cellulose involves the enzymatic action of cellulases (endoglucanases), cellobiohydrolases (exoglucanases), and β-glucosidases that act synergistically. The rate and efficiency of enzymatic hydrolysis of crystalline cellulose in vitro decline markedly with time, limiting the large-scale, cost-effective production of cellulosic biofuels. Several factors have been suggested to contribute to this phenomenon, but there is considerable disagreement regarding the relative importance of each. These earlier investigations were hampered by the inability to observe the disruption of crystalline cellulose and its subsequent hydrolysis directly. Here, we show the application of high-resolution atomic force microscopy to observe the swelling of a single crystalline cellulose fiber and its-hydrolysis in real time directly as catalyzed by a single cellulase, the industrially important cellulase 7B from Trichoderma reesei. Volume changes, the root-mean-square roughness, and rates of hydrolysis of the surfaces of single fibers were determined directly from the images acquired over time. Hydrolysis dominated the early stage of the experiment, and swelling dominated the later stage. The high-resolution images revealed that the combined action of initial hydrolysis followed by swelling exposed individual microfibrils and bundles of microfibrils, resulting in the loosening of the fiber structure and the exposure of microfibrils at the fiber surface. Both the hydrolysis and swelling were catalyzed by the native cellulase; under the same conditions, its isolated carbohydrate-binding module did not cause changes to crystalline cellulose. We anticipate that the application of our AFM-based analysis on other cellulolytic enzymes, alone and in combination, will provide significant insight into the process of cellulose biodegradation and greatly facilitate its application for the efficient and economical production of cellulosic ethanol.
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Affiliation(s)
- Jingpeng Wang
- Department of Chemistry, University of Guelph, Guelph, Ontario N1G 2W1, Canada
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71
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Jalak J, Kurašin M, Teugjas H, Väljamäe P. Endo-exo synergism in cellulose hydrolysis revisited. J Biol Chem 2012; 287:28802-15. [PMID: 22733813 DOI: 10.1074/jbc.m112.381624] [Citation(s) in RCA: 143] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Synergistic cooperation of different enzymes is a prerequisite for efficient degradation of cellulose. The conventional mechanistic interpretation of the synergism between randomly acting endoglucanases (EGs) and chain end-specific processive cellobiohydrolases (CBHs) is that EG-generated new chain ends on cellulose surface serve as starting points for CBHs. Here we studied the hydrolysis of bacterial cellulose (BC) by CBH TrCel7A and EG TrCel5A from Trichoderma reesei under both single-turnover and "steady state" conditions. Unaccountable by conventional interpretation, the presence of EG increased the rate constant of TrCel7A-catalyzed hydrolysis of BC in steady state. At optimal enzyme/substrate ratios, the "steady state" rate of synergistic hydrolysis became limited by the velocity of processive movement of TrCel7A on BC. A processivity value of 66 ± 7 cellobiose units measured for TrCel7A on (14)C-labeled BC was close to the leveling off degree of polymerization of BC, suggesting that TrCel7A cannot pass through the amorphous regions on BC and stalls. We propose a mechanism of endo-exo synergism whereby the degradation of amorphous regions by EG avoids the stalling of TrCel7A and leads to its accelerated recruitment. Hydrolysis of pretreated wheat straw suggested that this mechanism of synergism is operative also in the degradation of lignocellulose. Although both mechanisms of synergism are used in parallel, the contribution of conventional mechanism is significant only at high enzyme/substrate ratios.
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Affiliation(s)
- Jürgen Jalak
- Institute of Molecular and Cell Biology, University of Tartu, Vanemuise 46-138, 51014 Tartu, Estonia
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72
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Cellulose nanofibrils prepared from softwood cellulose by TEMPO/NaClO/NaClO₂ systems in water at pH 4.8 or 6.8. Int J Biol Macromol 2012; 51:228-34. [PMID: 22617623 DOI: 10.1016/j.ijbiomac.2012.05.016] [Citation(s) in RCA: 91] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2012] [Revised: 05/08/2012] [Accepted: 05/14/2012] [Indexed: 11/23/2022]
Abstract
Catalytic oxidation of softwood cellulose using NaClO and either 2,2,6,6-tetramethylpiperidine-1-oxyl (4-H-TEMPO) or 4-acetamido-TEMPO (4-AcNH-TEMPO) was applied with NaClO(2) used as a primary oxidant in an aqueous buffer at pH 4.8 or 6.8. When the 4-AcNH-TEMPO-mediated oxidation was applied to softwood cellulose in water at pH 4.8 and 40 °C, the carboxylate content rose to ∼1.3 mmol/g after reaction for 48 h and the DP(v) value was more than 1100. This 4-AcNH-TEMPO-oxidized softwood cellulose was mostly converted to individual nanofibrils by mechanical disintegration in water, with uniform widths of 3-4 nm and lengths greater than 1 μm.
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73
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Biomass Converting Enzymes as Industrial Biocatalysts for Fuels and Chemicals: Recent Developments. Catalysts 2012. [DOI: 10.3390/catal2020244] [Citation(s) in RCA: 95] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
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74
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Abstract
Cellulose is an important biopolymer primarily stored as plant cell wall material. Plant-synthesized cellulose forms elementary fibrils that are micrometers in length and 3-5 nm in dimensions. Cellulose is a dynamic structure, and its size and property vary in different cellulose-containing materials. Atomic force microscopy offers the capability of imaging surface structure at the subnanometer resolution and under nearly physiological conditions, therefore providing an ideal tool for cellulose characterization.
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Affiliation(s)
- Shi-You Ding
- National Renewable Energy Laboratory, Biosciences Center, Golden, CO, USA.
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75
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Marana SR. Structural and mechanistic fundamentals for designing of cellulases. Comput Struct Biotechnol J 2012; 2:e201209006. [PMID: 24688647 PMCID: PMC3962180 DOI: 10.5936/csbj.201209006] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2012] [Revised: 09/20/2012] [Accepted: 09/23/2012] [Indexed: 11/22/2022] Open
Affiliation(s)
- Sandro R Marana
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, CP 26077, São Paulo, 05513-970, SP, Brazil
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76
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Fox JM, Levine SE, Clark DS, Blanch HW. Initial- and Processive-Cut Products Reveal Cellobiohydrolase Rate Limitations and the Role of Companion Enzymes. Biochemistry 2011; 51:442-52. [DOI: 10.1021/bi2011543] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Jerome M. Fox
- Energy Biosciences Institute and ‡Department of
Chemical and Biomolecular Engineering, University of California, Berkeley, California 94720, United States
| | - Seth E. Levine
- Energy Biosciences Institute and ‡Department of
Chemical and Biomolecular Engineering, University of California, Berkeley, California 94720, United States
| | - Douglas S. Clark
- Energy Biosciences Institute and ‡Department of
Chemical and Biomolecular Engineering, University of California, Berkeley, California 94720, United States
| | - Harvey W. Blanch
- Energy Biosciences Institute and ‡Department of
Chemical and Biomolecular Engineering, University of California, Berkeley, California 94720, United States
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77
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Bubner P, Dohr J, Plank H, Mayrhofer C, Nidetzky B. Cellulases dig deep: in situ observation of the mesoscopic structural dynamics of enzymatic cellulose degradation. J Biol Chem 2011; 287:2759-65. [PMID: 22128148 PMCID: PMC3268433 DOI: 10.1074/jbc.m111.257717] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Enzymatic hydrolysis of cellulose is key for the production of second generation biofuels, which represent a long-standing leading area in the field of sustainable energy. Despite the wealth of knowledge about cellulase structure and function, the elusive mechanism by which these enzymes disintegrate the complex structure of their insoluble substrate, which is the gist of cellulose saccharification, is still unclear. We herein present a time-resolved structural characterization of the action of cellulases on a nano-flat cellulose preparation, which enabled us to overcome previous limitations, using atomic force microscopy (AFM). As a first step in substrate disintegration, elongated fissures emerge which develop into coniform cracks as disintegration continues. Detailed data analysis allowed tracing the surface evolution back to the dynamics of crack morphology. This, in turn, reflects the interplay between surface degradation inside and outside of the crack. We observed how small cracks evolved and initially increased in size. At a certain point, the crack diameter stagnated and then started decreasing again. Stagnation corresponds with a decrease in the total amount of surface which is fissured and thus leads to the conclusion that the surface hydrolysis “around” the cracks is proceeding more rapidly than inside the cracks. The mesoscopic view presented here is in good agreement with various mechanistic proposals from the past and allows a novel insight into the structural dynamics occurring on the cellulosic substrate through cellulase action.
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Affiliation(s)
- Patricia Bubner
- Institute of Biotechnology and Biochemical Engineering, Graz University of Technology, Petersgasse 12, A-8010 Graz, Austria
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78
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Igarashi K, Uchihashi T, Koivula A, Wada M, Kimura S, Okamoto T, Penttilä M, Ando T, Samejima M. Traffic jams reduce hydrolytic efficiency of cellulase on cellulose surface. Science 2011; 333:1279-82. [PMID: 21885779 DOI: 10.1126/science.1208386] [Citation(s) in RCA: 351] [Impact Index Per Article: 27.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
A deeper mechanistic understanding of the saccharification of cellulosic biomass could enhance the efficiency of biofuels development. We report here the real-time visualization of crystalline cellulose degradation by individual cellulase enzymes through use of an advanced version of high-speed atomic force microscopy. Trichoderma reesei cellobiohydrolase I (TrCel7A) molecules were observed to slide unidirectionally along the crystalline cellulose surface but at one point exhibited collective halting analogous to a traffic jam. Changing the crystalline polymorphic form of cellulose by means of an ammonia treatment increased the apparent number of accessible lanes on the crystalline surface and consequently the number of moving cellulase molecules. Treatment of this bulky crystalline cellulose simultaneously or separately with T. reesei cellobiohydrolase II (TrCel6A) resulted in a remarkable increase in the proportion of mobile enzyme molecules on the surface. Cellulose was completely degraded by the synergistic action between the two enzymes.
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Affiliation(s)
- Kiyohiko Igarashi
- Department of Biomaterial Sciences, Graduate School of Agricultural and Life Sciences, University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan.
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Ye Z, Lane AN, Willing GA, Berson RE. Scaled-up separation of cellobiohydrolase1 from a cellulase mixture by ion-exchange chromatography. Biotechnol Prog 2011; 27:1644-52. [DOI: 10.1002/btpr.696] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2011] [Revised: 04/27/2011] [Indexed: 11/10/2022]
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Fungal enzyme sets for plant polysaccharide degradation. Appl Microbiol Biotechnol 2011; 91:1477-92. [PMID: 21785931 PMCID: PMC3160556 DOI: 10.1007/s00253-011-3473-2] [Citation(s) in RCA: 355] [Impact Index Per Article: 27.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2011] [Revised: 06/27/2011] [Accepted: 07/10/2011] [Indexed: 02/01/2023]
Abstract
Enzymatic degradation of plant polysaccharides has many industrial applications, such as within the paper, food, and feed industry and for sustainable production of fuels and chemicals. Cellulose, hemicelluloses, and pectins are the main components of plant cell wall polysaccharides. These polysaccharides are often tightly packed, contain many different sugar residues, and are branched with a diversity of structures. To enable efficient degradation of these polysaccharides, fungi produce an extensive set of carbohydrate-active enzymes. The variety of the enzyme set differs between fungi and often corresponds to the requirements of its habitat. Carbohydrate-active enzymes can be organized in different families based on the amino acid sequence of the structurally related catalytic modules. Fungal enzymes involved in plant polysaccharide degradation are assigned to at least 35 glycoside hydrolase families, three carbohydrate esterase families and six polysaccharide lyase families. This mini-review will discuss the enzymes needed for complete degradation of plant polysaccharides and will give an overview of the latest developments concerning fungal carbohydrate-active enzymes and their corresponding families.
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