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Su M, Liu Y, Lyu J, Zhao S, Wang Y. Chemical and Structural Responses to Downregulated p-Hydroxycinnamoyl-Coenzyme A: Quinate/Shikimate p-Hydroxycinnamoyltransferase in Poplar Cell Walls. FRONTIERS IN PLANT SCIENCE 2022; 12:679230. [PMID: 35154167 PMCID: PMC8830424 DOI: 10.3389/fpls.2021.679230] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/11/2021] [Accepted: 12/22/2021] [Indexed: 06/14/2023]
Abstract
Unraveling the impact of lignin reduction on cell wall construction of poplar stems is important for accurate understanding the regulatory role of biosynthetic genes. However, few cell-level studies have been conducted on the changes in lignin, other important cell wall composition, and the structural properties of transgenic poplar stems at different developmental stages. In this work, the content and microdistributions of cell wall composition as well as the morphological characteristics of cells were studied for p-hydroxycinnamoyl-coenzyme A:quinate/shikimate p-hydroxycinnamoyltransferase (HCT) downregulated transgenic poplar 84K (Populus alba × P. glandulosa cl. '84k') at different developmental stages. Results show that the lignin contents of the upper, middle, and basal parts of HCT transgenic poplar stems were significantly decreased by 10.84, 7.40, and 7.75%, respectively; and the cellulose contents increased by 8.20, 6.45, and 3.31%, respectively, compared with the control group. The cellulose/lignin ratio of HCT transgenic poplars was therefore increased, especially in the upper sections, where it was 23.2% higher. Raman results indicate the appearance of p-hydroxyphenyl units (H) and a decrease in the ratio of syringyl/guaiacyl (S/G) lignin monomers in fiber cell walls of HCT transgenic poplars. In addition, microstructure observations revealed that the fiber and vessel cells of the HCT transgenic poplars exhibited thin cell walls and large lumen diameters. Compared with the control group, the cell wall thickness of fiber and vessel cells decreased by 6.50 and 10.93% on average, respectively. There was a 13.6% decrease in the average ratio of the cell wall thickness to the lumen diameter and an increase in fiber length and width of 5.60 and 6.11%, respectively. In addition, downregulation of HCT did not change the orientation of cellulosic microfibrils, but it led to an 11.1% increase of the cellulose crystallinity in cell walls compared to the control poplars. The information obtained herein could lead to a better understanding of the effects of genetic modifications on wood cell walls.
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Affiliation(s)
- Minglei Su
- Research Institute of Wood Industry, Chinese Academy of Forestry, Beijing, China
- Key Laboratory of National Forestry and Grassland Administration/Beijing for Bamboo and Rattan Science and Technology, International Centre for Bamboo and Rattan, Beijing, China
| | - Yingli Liu
- State Key Laboratory of Tree Genetics and Breeding, Research Institute of Forestry, Chinese Academy of Forestry, Beijing, China
| | - Jianxiong Lyu
- Research Institute of Wood Industry, Chinese Academy of Forestry, Beijing, China
| | - Shutang Zhao
- State Key Laboratory of Tree Genetics and Breeding, Research Institute of Forestry, Chinese Academy of Forestry, Beijing, China
| | - Yurong Wang
- Research Institute of Wood Industry, Chinese Academy of Forestry, Beijing, China
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Strategies towards Reduction of Cellulases Consumption: Debottlenecking the Economics of Lignocellulosics Valorization Processes. POLYSACCHARIDES 2021. [DOI: 10.3390/polysaccharides2020020] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Lignocellulosic residues have been receiving growing interest as a promising source of polysaccharides, which can be converted into a variety of compounds, ranging from biofuels to bioplastics. Most of these can replace equivalent products traditionally originated from petroleum, hence representing an important environmental advantage. Lignocellulosic materials are theoretically unlimited, cheaper and may not compete with food crops. However, the conversion of these materials to simpler sugars usually requires cellulolytic enzymes. Being still associated with a high cost of production, cellulases are commonly considered as one of the main obstacles in the economic valorization of lignocellulosics. This work provides a brief overview of some of the most studied strategies that can allow an important reduction of cellulases consumption, hence improving the economy of lignocellulosics conversion. Cellulases recycling is initially discussed regarding the main processes to recover active enzymes and the most important factors that may affect enzyme recyclability. Similarly, the potential of enzyme immobilization is analyzed with a special focus on the contributions that some elements of the process can offer for prolonged times of operation and improved enzyme stability and robustness. Finally, the emergent concept of consolidated bioprocessing (CBP) is also described in the particular context of a potential reduction of cellulases consumption.
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Østby H, Hansen LD, Horn SJ, Eijsink VGH, Várnai A. Enzymatic processing of lignocellulosic biomass: principles, recent advances and perspectives. J Ind Microbiol Biotechnol 2020; 47:623-657. [PMID: 32840713 PMCID: PMC7658087 DOI: 10.1007/s10295-020-02301-8] [Citation(s) in RCA: 63] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2020] [Accepted: 07/30/2020] [Indexed: 02/06/2023]
Abstract
Efficient saccharification of lignocellulosic biomass requires concerted development of a pretreatment method, an enzyme cocktail and an enzymatic process, all of which are adapted to the feedstock. Recent years have shown great progress in most aspects of the overall process. In particular, increased insights into the contributions of a wide variety of cellulolytic and hemicellulolytic enzymes have improved the enzymatic processing step and brought down costs. Here, we review major pretreatment technologies and different enzyme process setups and present an in-depth discussion of the various enzyme types that are currently in use. We pay ample attention to the role of the recently discovered lytic polysaccharide monooxygenases (LPMOs), which have led to renewed interest in the role of redox enzyme systems in lignocellulose processing. Better understanding of the interplay between the various enzyme types, as they may occur in a commercial enzyme cocktail, is likely key to further process improvements.
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Affiliation(s)
- Heidi Østby
- Faculty of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences (NMBU), P.O. Box 5003, 1432, Aas, Norway
| | - Line Degn Hansen
- Faculty of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences (NMBU), P.O. Box 5003, 1432, Aas, Norway
| | - Svein J Horn
- Faculty of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences (NMBU), P.O. Box 5003, 1432, Aas, Norway
| | - Vincent G H Eijsink
- Faculty of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences (NMBU), P.O. Box 5003, 1432, Aas, Norway
| | - Anikó Várnai
- Faculty of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences (NMBU), P.O. Box 5003, 1432, Aas, Norway.
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Djajadi DT, Pihlajaniemi V, Rahikainen J, Kruus K, Meyer AS. Cellulases adsorb reversibly on biomass lignin. Biotechnol Bioeng 2018; 115:2869-2880. [PMID: 30132790 PMCID: PMC6282830 DOI: 10.1002/bit.26820] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2018] [Revised: 07/30/2018] [Accepted: 08/13/2018] [Indexed: 12/14/2022]
Abstract
Adsorption of cellulases onto lignin is considered a major factor in retarding enzymatic cellulose degradation of lignocellulosic biomass. However, the adsorption mechanisms and kinetics are not well understood for individual types of cellulases. This study examines the binding affinity, kinetics of adsorption, and competition of four monocomponent cellulases of Trichoderma reesei during adsorption onto lignin.
TrCel7A,
TrCel6A,
TrCel7B, and
TrCel5A were radiolabeled for adsorption experiments on lignin‐rich residues (LRRs) isolated from hydrothermally pretreated spruce (L‐HPS) and wheat straw (L‐HPWS), respectively. On the basis of adsorption isotherms fitted to the Langmuir model, the ranking of binding affinities was
TrCel5A >
TrCel6A >
TrCel7B >
TrCel7A on both types of LRRs. The enzymes had a higher affinity to the L‐HPS than to the L‐HPWS. Adsorption experiments with dilution after 1 and 24 hr and kinetic modeling were performed to quantify any irreversible binding over time. Models with reversible binding parameters fitted well and can explain the results obtained. The adsorption constants obtained from the reversible models agreed with the fitted Langmuir isotherms and suggested that reversible adsorption–desorption existed at equilibrium. Competitive binding experiments showed that individual types of cellulases competed for binding sites on the lignin and the adsorption data fitted the Langmuir adsorption model. Overall, the data strongly indicate that the adsorption of cellulases onto lignin is reversible and the findings have implications for the development of more efficient cellulose degrading enzymes.
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Affiliation(s)
- Demi T Djajadi
- Department of Chemical and Biochemical Engineering, Technical University of Denmark, Kongens Lyngby, Denmark
| | | | | | | | - Anne S Meyer
- Department of Chemical and Biochemical Engineering, Technical University of Denmark, Kongens Lyngby, Denmark
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Djajadi DT, Jensen MM, Oliveira M, Jensen A, Thygesen LG, Pinelo M, Glasius M, Jørgensen H, Meyer AS. Lignin from hydrothermally pretreated grass biomass retards enzymatic cellulose degradation by acting as a physical barrier rather than by inducing nonproductive adsorption of enzymes. BIOTECHNOLOGY FOR BIOFUELS 2018; 11:85. [PMID: 29619081 PMCID: PMC5880018 DOI: 10.1186/s13068-018-1085-0] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/03/2018] [Accepted: 03/17/2018] [Indexed: 05/03/2023]
Abstract
BACKGROUND Lignin is known to hinder efficient enzymatic conversion of lignocellulose in biorefining processes. In particular, nonproductive adsorption of cellulases onto lignin is considered a key mechanism to explain how lignin retards enzymatic cellulose conversion in extended reactions. RESULTS Lignin-rich residues (LRRs) were prepared via extensive enzymatic cellulose degradation of corn stover (Zea mays subsp. mays L.), Miscanthus × giganteus stalks (MS) and wheat straw (Triticum aestivum L.) (WS) samples that each had been hydrothermally pretreated at three severity factors (log R0) of 3.65, 3.83 and 3.97. The LRRs had different residual carbohydrate levels-the highest in MS; the lowest in WS. The residual carbohydrate was not traceable at the surface of the LRRs particles by ATR-FTIR analysis. The chemical properties of the lignin in the LRRs varied across the three types of biomass, but monolignols composition was not affected by the severity factor. When pure cellulose was added to a mixture of LRRs and a commercial cellulolytic enzyme preparation, the rate and extent of glucose release were unaffected by the presence of LRRs regardless of biomass type and severity factor, despite adsorption of the enzymes to the LRRs. Since the surface of the LRRs particles were covered by lignin, the data suggest that the retardation of enzymatic cellulose degradation during extended reaction on lignocellulosic substrates is due to physical blockage of the access of enzymes to the cellulose caused by the gradual accumulation of lignin at the surface of the biomass particles rather than by nonproductive enzyme adsorption. CONCLUSIONS The study suggests that lignin from hydrothermally pretreated grass biomass retards enzymatic cellulose degradation by acting as a physical barrier blocking the access of enzymes to cellulose rather than by inducing retardation through nonproductive adsorption of enzymes.
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Affiliation(s)
- Demi T. Djajadi
- Department of Chemical and Biochemical Engineering, Technical University of Denmark, Søltofts Plads Building 229, 2800 Kongens Lyngby, Denmark
| | - Mads M. Jensen
- Department of Chemistry, Aarhus University, Langelandsgade 140, 8000 Aarhus C, Denmark
| | - Marlene Oliveira
- Department of Chemical and Biochemical Engineering, Technical University of Denmark, Søltofts Plads Building 229, 2800 Kongens Lyngby, Denmark
| | - Anders Jensen
- Department of Geosciences and Natural Resource Management, University of Copenhagen, Rolighedsvej 23, 1958 Frederiksberg C, Denmark
| | - Lisbeth G. Thygesen
- Department of Geosciences and Natural Resource Management, University of Copenhagen, Rolighedsvej 23, 1958 Frederiksberg C, Denmark
| | - Manuel Pinelo
- Department of Chemical and Biochemical Engineering, Technical University of Denmark, Søltofts Plads Building 229, 2800 Kongens Lyngby, Denmark
| | - Marianne Glasius
- Department of Chemistry, Aarhus University, Langelandsgade 140, 8000 Aarhus C, Denmark
| | - Henning Jørgensen
- Department of Chemical and Biochemical Engineering, Technical University of Denmark, Søltofts Plads Building 229, 2800 Kongens Lyngby, Denmark
- Present Address: Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, 1871 Frederiksberg C, Denmark
| | - Anne S. Meyer
- Department of Chemical and Biochemical Engineering, Technical University of Denmark, Søltofts Plads Building 229, 2800 Kongens Lyngby, Denmark
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Banoth C, Sunkar B, Tondamanati PR, Bhukya B. Improved physicochemical pretreatment and enzymatic hydrolysis of rice straw for bioethanol production by yeast fermentation. 3 Biotech 2017; 7:334. [PMID: 28955631 DOI: 10.1007/s13205-017-0980-6] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2017] [Accepted: 09/14/2017] [Indexed: 10/18/2022] Open
Abstract
Lignocellulosic biomass such as agricultural and forest residues are considered as an alternative, inexpensive, renewable, and abundant source for fuel ethanol production. In the present study, three different pretreatment methods for rice straw were carried out to investigate the maximum lignin removal for subsequent bioethanol fermentation. The chemical pretreatments of rice straw were optimized under different pretreatment severity conditions in the range of 1.79-2.26. Steam explosion of rice straw at 170 °C for 10 min, sequentially treated with 2% (w/v) KOH (SEKOH) in autoclave at 121 °C for 30 min, resulted in 85 ± 2% delignification with minimum sugar loss. Combined pretreatment of steam explosion and KOH at severity factor (SF 3.10) showed improved cellulose fraction of biomass. Furthermore, enzymatic hydrolysis at 30 FPU/g enzyme loading resulted in 664.0 ± 5.39 mg/g sugar yield with 82.60 ± 1.7% saccharification efficiency. Consequently, the hydrolysate of SEKOH with 58.70 ± 1.52 g/L sugars when fermented with Saccharomyces cerevisiae OBC14 showed 26.12 ± 1.24 g/L ethanol, 0.44 g/g ethanol yield with 87.03 ± 1.6% fermentation efficiency.
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Predicting the ethanol potential of wheat straw using near-infrared spectroscopy and chemometrics: The challenge of inherently intercorrelated response functions. Anal Chim Acta 2017; 962:15-23. [DOI: 10.1016/j.aca.2017.02.001] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2016] [Revised: 01/31/2017] [Accepted: 02/02/2017] [Indexed: 11/23/2022]
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Hu BB, Zhu MJ. Enhanced hydrogen production and biological saccharification from spent mushroom compost by Clostridium thermocellum 27405 supplemented with recombinant β-glucosidases. INTERNATIONAL JOURNAL OF HYDROGEN ENERGY 2017; 42:7866-7874. [DOI: 10.1016/j.ijhydene.2017.01.031] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/01/2023]
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Auxenfans T, Crônier D, Chabbert B, Paës G. Understanding the structural and chemical changes of plant biomass following steam explosion pretreatment. BIOTECHNOLOGY FOR BIOFUELS 2017; 10:36. [PMID: 28191037 PMCID: PMC5297051 DOI: 10.1186/s13068-017-0718-z] [Citation(s) in RCA: 98] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/03/2016] [Accepted: 01/26/2017] [Indexed: 05/09/2023]
Abstract
BACKGROUND Biorefining of lignocellulosic biomass has become one of the most valuable alternatives for the production of multi-products such as biofuels. Pretreatment is a prerequisite to increase the enzymatic conversion of the recalcitrant lignocellulose. However, there is still considerable debate regarding the key features of biomass impacting the cellulase accessibility. In this study, we evaluate the structural and chemical features of three different representative biomasses (Miscanthus × giganteus, poplar and wheat straw), before and after steam explosion pretreatment at increasing severities, by monitoring chemical analysis, SEM, FTIR and 2D NMR. RESULTS Regardless the biomass type, combined steam explosion pretreatment with dilute sulfuric acid impregnation resulted in significant improvement of the cellulose conversion. Chemical analyses revealed that the pretreatment selectively degraded the hemicellulosic fraction and associated cross-linking ferulic acids. As a result, the pretreated residues contained mostly cellulosic glucose and lignin. In addition, the pretreatment directly affected the cellulose crystallinity but these variations were dependent upon the biomass type. Important chemical modifications also occurred in lignin since the β-O-4' aryl-ether linkages were found to be homolytically cleaved, followed by some recoupling/recondensation to β-β' and β-5' linkages, regardless the biomass type. Finally, 2D NMR analysis of the whole biomass showed that the pretreatment preferentially degraded the syringyl-type lignin fractions in miscanthus and wheat straw while it was not affected in the pretreated poplar samples. CONCLUSIONS Our findings provide an enhanced understanding of parameters impacting biomass recalcitrance, which can be easily generalized to both woody and non-woody biomass species. Results indeed suggest that the hemicellulose removal accompanied by the significant reduction in the cross-linking phenolic acids and the redistribution of lignin are strongly correlated with the enzymatic saccharification, by loosening the cell wall structure thus allowing easier cellulase accessibility. By contrast, we have shown that the changes in the syringyl/guaiacyl ratio and the cellulose crystallinity do not seem to be relevant factors in assessing the enzymatic digestibility. Some biomass type-dependent and easily measurable FTIR factors are highly correlated to saccharification.
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Affiliation(s)
- Thomas Auxenfans
- FARE Laboratory, INRA, Université de Reims Champagne-Ardenne, 51100 Reims, France
| | - David Crônier
- FARE Laboratory, INRA, Université de Reims Champagne-Ardenne, 51100 Reims, France
| | - Brigitte Chabbert
- FARE Laboratory, INRA, Université de Reims Champagne-Ardenne, 51100 Reims, France
| | - Gabriel Paës
- FARE Laboratory, INRA, Université de Reims Champagne-Ardenne, 51100 Reims, France
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Djajadi DT, Hansen AR, Jensen A, Thygesen LG, Pinelo M, Meyer AS, Jørgensen H. Surface properties correlate to the digestibility of hydrothermally pretreated lignocellulosic Poaceae biomass feedstocks. BIOTECHNOLOGY FOR BIOFUELS 2017; 10:49. [PMID: 28250817 PMCID: PMC5322652 DOI: 10.1186/s13068-017-0730-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/11/2017] [Accepted: 02/10/2017] [Indexed: 05/08/2023]
Abstract
BACKGROUND Understanding factors that govern lignocellulosic biomass recalcitrance is a prerequisite for designing efficient 2nd generation biorefining processes. However, the reasons and mechanisms responsible for quantitative differences in enzymatic digestibility of various biomass feedstocks in response to hydrothermal pretreatment at different severities are still not sufficiently understood. RESULTS Potentially important lignocellulosic feedstocks for biorefining, corn stover (Zea mays subsp. mays L.), stalks of Miscanthus × giganteus, and wheat straw (Triticum aestivum L.) were systematically hydrothermally pretreated; each at three different severities of 3.65, 3.83, and 3.97, respectively, and the enzymatic digestibility was assessed. Pretreated samples of Miscanthus × giganteus stalks were the least digestible among the biomass feedstocks producing ~24 to 66.6% lower glucose yields than the other feedstocks depending on pretreatment severity and enzyme dosage. Bulk biomass composition analyses, 2D nuclear magnetic resonance, and comprehensive microarray polymer profiling were not able to explain the observed differences in recalcitrance among the pretreated feedstocks. However, methods characterizing physical and chemical features of the biomass surfaces, specifically contact angle measurements (wettability) and attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy (surface biopolymer composition) produced data correlating pretreatment severity and enzymatic digestibility, and they also revealed differences that correlated to enzymatic glucose yield responses among the three different biomass types. CONCLUSION The study revealed that to a large extent, factors related to physico-chemical surface properties, namely surface wettability as assessed by contact angle measurements and surface content of hemicellulose, lignin, and wax as assessed by ATR-FTIR rather than bulk biomass chemical composition correlated to the recalcitrance of the tested biomass types. The data provide new insight into how hydrothermal pretreatment severity affects surface properties of key Poaceae lignocellulosic biomass and may help design new approaches to overcome biomass recalcitrance.
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Affiliation(s)
- Demi T. Djajadi
- Department of Chemical and Biochemical Engineering, Technical University of Denmark, Søltofts Plads Building 229, 2800 Kongens Lyngby, Denmark
| | - Aleksander R. Hansen
- Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, 1871 Kongens Lyngby, Denmark
| | - Anders Jensen
- Department of Geosciences and Natural Resource Management, University of Copenhagen, Rolighedsvej 23, 1958 Frederiksberg C, Denmark
| | - Lisbeth G. Thygesen
- Department of Geosciences and Natural Resource Management, University of Copenhagen, Rolighedsvej 23, 1958 Frederiksberg C, Denmark
| | - Manuel Pinelo
- Department of Chemical and Biochemical Engineering, Technical University of Denmark, Søltofts Plads Building 229, 2800 Kongens Lyngby, Denmark
| | - Anne S. Meyer
- Department of Chemical and Biochemical Engineering, Technical University of Denmark, Søltofts Plads Building 229, 2800 Kongens Lyngby, Denmark
| | - Henning Jørgensen
- Department of Chemical and Biochemical Engineering, Technical University of Denmark, Søltofts Plads Building 229, 2800 Kongens Lyngby, Denmark
- Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, 1871 Kongens Lyngby, Denmark
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Li M, Pu Y, Ragauskas AJ. Current Understanding of the Correlation of Lignin Structure with Biomass Recalcitrance. Front Chem 2016; 4:45. [PMID: 27917379 PMCID: PMC5114238 DOI: 10.3389/fchem.2016.00045] [Citation(s) in RCA: 137] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2016] [Accepted: 11/02/2016] [Indexed: 12/22/2022] Open
Abstract
Lignin, a complex aromatic polymer in terrestrial plants, contributes significantly to biomass recalcitrance to microbial and/or enzymatic deconstruction. To reduce biomass recalcitrance, substantial endeavors have been exerted on pretreatment and lignin engineering in the past few decades. Lignin removal and/or alteration of lignin structure have been shown to result in reduced biomass recalcitrance with improved cell wall digestibility. While high lignin content is usually a barrier to a cost-efficient application of bioresources to biofuels, the direct correlation of lignin structure and its concomitant properties with biomass remains unclear due to the complexity of cell wall and lignin structure. Advancement in application of biorefinery to production of biofuels, chemicals, and bio-derived materials necessitates a fundamental understanding of the relationship of lignin structure and biomass recalcitrance. In this mini-review, we focus on recent investigations on the influence of lignin chemical properties on bioprocessability-pretreatment and enzymatic hydrolysis of biomass. Specifically, lignin-enzyme interactions and the effects of lignin compositional units, hydroxycinnamates, and lignin functional groups on biomass recalcitrance have been highlighted, which will be useful not only in addressing biomass recalcitrance but also in deploying renewable lignocelluloses efficiently.
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Affiliation(s)
- Mi Li
- BioEnergy Science Center, Biosciences Division, Joint Institute of Biological Science, Oak Ridge National Laboratory Oak Ridge, TN, USA
| | - Yunqiao Pu
- BioEnergy Science Center, Biosciences Division, Joint Institute of Biological Science, Oak Ridge National Laboratory Oak Ridge, TN, USA
| | - Arthur J Ragauskas
- BioEnergy Science Center, Biosciences Division, Joint Institute of Biological Science, Oak Ridge National LaboratoryOak Ridge, TN, USA; Department of Chemical and Bimolecular Engineering, University of Tennessee KnoxvilleKnoxville, TN, USA; Department of Forestry, Wildlife, and Fisheries, Center for Renewable Carbon, University Tennessee Institute of AgricultureKnoxville, TN, USA
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A. L. Rocha V, N. Maeda R, Pereira N, F. Kern M, Elias L, Simister R, Steele-King C, Gómez LD, McQueen-Mason SJ. Characterization of the cellulolytic secretome ofTrichoderma harzianumduring growth on sugarcane bagasse and analysis of the activity boosting effects of swollenin. Biotechnol Prog 2016; 32:327-36. [DOI: 10.1002/btpr.2217] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2015] [Revised: 10/02/2015] [Indexed: 01/21/2023]
Affiliation(s)
- Vanessa A. L. Rocha
- LADEBIO, Centre of Biofuels, Oil and its Derivatives, School of Chemistry; Department of Biochemical Engineering, Centre of Technology, Federal University of Rio De Janeiro; Rio De Janeiro 21941-909 Brazil
| | - Roberto N. Maeda
- LADEBIO, Centre of Biofuels, Oil and its Derivatives, School of Chemistry; Department of Biochemical Engineering, Centre of Technology, Federal University of Rio De Janeiro; Rio De Janeiro 21941-909 Brazil
| | - Nei Pereira
- LADEBIO, Centre of Biofuels, Oil and its Derivatives, School of Chemistry; Department of Biochemical Engineering, Centre of Technology, Federal University of Rio De Janeiro; Rio De Janeiro 21941-909 Brazil
| | - Marcelo F. Kern
- MasonCNAP, Dept. of Biology; University of York; Wentworth Way, York YO10 5DD U.K
| | - Luisa Elias
- MasonCNAP, Dept. of Biology; University of York; Wentworth Way, York YO10 5DD U.K
| | - Rachael Simister
- MasonCNAP, Dept. of Biology; University of York; Wentworth Way, York YO10 5DD U.K
| | - Clare Steele-King
- MasonCNAP, Dept. of Biology; University of York; Wentworth Way, York YO10 5DD U.K
| | - Leonardo D. Gómez
- MasonCNAP, Dept. of Biology; University of York; Wentworth Way, York YO10 5DD U.K
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Wang W, Zhu Y, Du J, Yang Y, Jin Y. Influence of lignin addition on the enzymatic digestibility of pretreated lignocellulosic biomasses. BIORESOURCE TECHNOLOGY 2015; 181:7-12. [PMID: 25625461 DOI: 10.1016/j.biortech.2015.01.026] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/06/2014] [Revised: 01/06/2015] [Accepted: 01/08/2015] [Indexed: 05/02/2023]
Abstract
The presence of lignin in lignocellulosic biomass is correlated with its enzymatic digestibility. Their correlation and mechanism have been investigated widely but have not been elucidated clearly. In this study, hydrophilic sulfonated lignin and hydrophobic kraft lignin were introduced into the enzymatic hydrolysis process to investigate their effects on the enzymatic digestibility of different pretreated lignocellulose. The influence of lignin addition on the enzymatic digestibility varied with both introduced lignin type and the pretreatment methods of substrates. Slight enhancement of enzymatic hydrolysis was observed for all substrates by adding kraft lignin. The addition of sulfonated lignin could effectively improve the enzymatic digestibility of green liquor and acidic bisulfite pretreated materials, but had little effect on sulfite-formaldehyde pretreated samples. The enzymatic digestibility of green liquor pretreated masson pine increased from 42% without lignin addition to 75% with 0.3g/g-substrate sulfonated lignin addition.
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Affiliation(s)
- Wangxia Wang
- Jiangsu Provincial Key Lab of Pulp and Paper Science and Technology, Nanjing Forestry University, Nanjing 210037, China
| | - Yangsu Zhu
- Jiangsu Provincial Key Lab of Pulp and Paper Science and Technology, Nanjing Forestry University, Nanjing 210037, China
| | - Jing Du
- Jiangsu Provincial Key Lab of Pulp and Paper Science and Technology, Nanjing Forestry University, Nanjing 210037, China
| | - Yiqin Yang
- Jiangsu Provincial Key Lab of Pulp and Paper Science and Technology, Nanjing Forestry University, Nanjing 210037, China
| | - Yongcan Jin
- Jiangsu Provincial Key Lab of Pulp and Paper Science and Technology, Nanjing Forestry University, Nanjing 210037, China.
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Gomes D, Rodrigues AC, Domingues L, Gama M. Cellulase recycling in biorefineries—is it possible? Appl Microbiol Biotechnol 2015; 99:4131-43. [DOI: 10.1007/s00253-015-6535-z] [Citation(s) in RCA: 57] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2015] [Revised: 03/09/2015] [Accepted: 03/11/2015] [Indexed: 11/28/2022]
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15
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Greene ER, Himmel ME, Beckham GT, Tan Z. Glycosylation of Cellulases: Engineering Better Enzymes for Biofuels. Adv Carbohydr Chem Biochem 2015; 72:63-112. [PMID: 26613815 DOI: 10.1016/bs.accb.2015.08.001] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
Cellulose in plant cell walls is the largest reservoir of renewable carbon on Earth. The saccharification of cellulose from plant biomass into soluble sugars can be achieved using fungal and bacterial cellulolytic enzymes, cellulases, and further converted into fuels and chemicals. Most fungal cellulases are both N- and O-glycosylated in their native form, yet the consequences of glycosylation on activity and structure are not fully understood. Studying protein glycosylation is challenging as glycans are extremely heterogeneous, stereochemically complex, and glycosylation is not under direct genetic control. Despite these limitations, many studies have begun to unveil the role of cellulase glycosylation, especially in the industrially relevant cellobiohydrolase from Trichoderma reesei, Cel7A. Glycosylation confers many beneficial properties to cellulases including enhanced activity, thermal and proteolytic stability, and structural stabilization. However, glycosylation must be controlled carefully as such positive effects can be dampened or reversed. Encouragingly, methods for the manipulation of glycan structures have been recently reported that employ genetic tuning of glycan-active enzymes expressed from homogeneous and heterologous fungal hosts. Taken together, these studies have enabled new strategies for the exploitation of protein glycosylation for the production of enhanced cellulases for biofuel production.
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Teramura H, Oshima T, Matsuda F, Sasaki K, Ogino C, Yamasaki M, Kondo A. Glucose content in the liquid hydrolysate after dilute acid pretreatment is affected by the starch content in rice straw. BIORESOURCE TECHNOLOGY 2013; 149:520-524. [PMID: 24140898 DOI: 10.1016/j.biortech.2013.09.109] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/23/2013] [Revised: 09/20/2013] [Accepted: 09/24/2013] [Indexed: 06/02/2023]
Abstract
Lignocellulosic biomass, such as rice straw, is often utilized as a bioresource after being hydrolyzed using dilute acid and separated into liquid hydrolysate and acid-insoluble residue. However, the biomass component that determines the distribution between liquid hydrolysate and acid-insoluble residue has not yet been clarified. In this study, the glucose content in the liquid hydrolysate and weight of acid-insoluble residue of 13 rice cultivars were analyzed. Starch content was positively correlated with glucose content in the liquid hydrolysate, and negatively correlated with acid-insoluble residue weight. These results indicate that the glucose in the liquid hydrolysate is mainly liberated from starch rather than cellulose in the rice straw. These observations suggest that starch content is a good indicator of the glucose distribution between the liquid hydrolysate and insoluble residue.
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Affiliation(s)
- Hiroshi Teramura
- Department of Chemical Science and Engineering, Graduate School of Engineering, Kobe University, 1-1 Rokkodaicho, Nada-ku, Kobe, Hyogo 657-8501, Japan
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Barsberg S, Rasmussen HN, Kodahl N. Composition of Cypripedium calceolus (Orchidaceae) seeds analyzed by attenuated total reflectance IR spectroscopy: in search of understanding longevity in the ground. AMERICAN JOURNAL OF BOTANY 2013; 100:2066-73. [PMID: 24070862 DOI: 10.3732/ajb.1200646] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
PREMISE OF THE STUDY Orchid seeds are minute and covered with a thin coat, yet they often have a long life after dispersal. They are notorious for low and irregular germination, in nature as well as in vitro. Since orchids are often rare species of conservational and commercial interest, reproduction by seeds is an important concern. The purpose of this study was to learn more about the resilience of these highly specialized seeds and stimulatory processes toward germination. • METHODS We studied testa and embryos of Cypripedium calceolus to identify natural components in intact seeds and the impact of 7 yr in soil in its natural habitat. We also analyzed the effects of Ca(OCl)2, used technically to enhance germination for cultivation in vitro. For the first time with this kind of plant material, we used attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy, an ideal method for minute sample sizes and surface selectivity. Thus, we could link treatments with changes in seed surface chemistry. • KEY RESULTS A lignin-like polymer is an essential testa component that undergoes degradation by soil or hypochlorite processes. In both cases, we found a build-up of CaCO3 on the testa, which could interact with lignin to enhance germination. Very minor changes occurred in embryo reserve nutrient content after a long sojourn underground, which supports their continued viability. • CONCLUSIONS We suggest that degradation of lignin and enrichment of the testa surface with CaCO3 are important stimulants of germination both in the habitat and during laboratory sowing.
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Affiliation(s)
- Søren Barsberg
- Department of Geosciences and Natural Resource Management, University of Copenhagen, Rolighedsvej 23, 1958 Frederiksberg C, Copenhagen, Denmark
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18
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Hansen MAT, Hidayat BJ, Mogensen KK, Jeppesen MD, Jørgensen B, Johansen KS, Thygesen LG. Enzyme affinity to cell types in wheat straw (Triticum aestivum L.) before and after hydrothermal pretreatment. BIOTECHNOLOGY FOR BIOFUELS 2013; 6:54. [PMID: 23590820 PMCID: PMC3650653 DOI: 10.1186/1754-6834-6-54] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/18/2012] [Accepted: 04/10/2013] [Indexed: 05/05/2023]
Abstract
BACKGROUND Wheat straw used for bioethanol production varies in enzymatic digestibility according to chemical structure and composition of cell walls and tissues. In this work, the two biologically different wheat straw organs, leaves and stems, are described together with the effects of hydrothermal pretreatment on chemical composition, tissue structure, enzyme adhesion and digestion. To highlight the importance of inherent cell wall characteristics and the diverse effects of mechanical disruption and biochemical degradation, separate leaves and stems were pretreated on lab-scale and their tissue structures maintained mostly intact for image analysis. Finally, samples were enzymatically hydrolysed to correlate digestibility to chemical composition, removal of polymers, tissue composition and disruption, particle size and enzyme adhesion as a result of pretreatment and wax removal. For comparison, industrially pretreated wheat straw from Inbicon A/S was included in all the experiments. RESULTS Within the same range of pretreatment severities, industrial pretreatment resulted in most hemicellulose and epicuticular wax/cutin removal compared to lab-scale pretreated leaves and stems but also in most re-deposition of lignin on the surface. Tissues were furthermore degraded from tissues into individual cells while lab-scale pretreated samples were structurally almost intact. In both raw leaves and stems, endoglucanase and exoglucanase adhered most to parenchyma cells; after pretreatment, to epidermal cells in all the samples. Despite heavy tissue disruption, industrially pretreated samples were not as susceptible to enzymatic digestion as lab-scale pretreated leaves while lab-scale pretreated stems were the least digestible. CONCLUSIONS Despite preferential enzyme adhesion to epidermal cells after hydrothermal pretreatment, our results suggest that the single most important factor determining wheat straw digestibility is the fraction of parenchyma cells rather than effective tissue disruption.
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Affiliation(s)
- Mads AT Hansen
- Forest and Landscape, University of Copenhagen, Rolighedsvej 23, Frederiksberg C DK-1958, Denmark
| | - Budi J Hidayat
- Forest and Landscape, University of Copenhagen, Rolighedsvej 23, Frederiksberg C DK-1958, Denmark
| | - Kit K Mogensen
- Inbicon A/S, Kraftværksvej 5, Skærbæk, Fredericia DK-7000, Denmark
| | | | - Bodil Jørgensen
- Department of Agriculture and Ecology/Department of Plant and Environment Sciences, University of Copenhagen, Thorvaldsensvej 40, Frederiksberg C DK-1871, Denmark
| | | | - Lisbeth G Thygesen
- Forest and Landscape, University of Copenhagen, Rolighedsvej 23, Frederiksberg C DK-1958, Denmark
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