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Bao X, Guo G, Huo W, Li Q, Xu Q, Chen L. Ensiling pretreatment fortified with laccase and microbial inoculants enhances biomass preservation and bioethanol production of alfalfa stems. THE SCIENCE OF THE TOTAL ENVIRONMENT 2023; 857:159442. [PMID: 36252666 DOI: 10.1016/j.scitotenv.2022.159442] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/17/2022] [Revised: 09/18/2022] [Accepted: 10/11/2022] [Indexed: 06/16/2023]
Abstract
This study investigated the potential of ensiling pretreatment fortified with laccase and a lactic acid bacteria (LAB) inoculant on improving the utilization of alfalfa stems for bioethanol production. The alfalfa stems were ensiled with no additives (Con), 0.04 % laccase (LA), a LAB inoculant containing Pediococcus pentosaceus at 1 × 106 fresh weight (FW) and Pediococcus acidilactici at 3 × 105 cfu/g FW (PP), and a combination of LA and PP (LAP) for 120 days. By reshaping the bacterial community structure of alfalfa stem silages toward a higher abundance of Lactobacillus, the addition of laccase and LAB inoculant either alone or in combination facilitated lactic acid fermentation to reduce fermentation losses, as evidenced by low concentrations of ammonia nitrogen (53.7 to 68.9 g/kg total nitrogen) and ethanol (2.63 to 3.55 g/kg dry matter). All additive treatments increased lignocellulose degradation and soluble sugars concentrations of alfalfa stem silages. Due to delignification and polyphenol removal, glucan and xylan conversion (70.3 % vs. 35.7 % and 51.6 % vs. 27.9 %, respectively) and ethanol conversion efficiency (53.9 % vs. 26.4 %) of alfalfa stems were greatly increased by ensiling fortified with LA versus Con, and these variables (79.8 % for glucan, 58.7 % for xylan, and 60.1 % for ethanol conversion efficiency) were further enhanced with a synergistic effect of LA and PP fortification. The spearman correlation analysis revealed that bioethanol fermentation of silage biomass was closely related to ensiling parameters and total phenols. In conclusion, ensiling pretreatment with LA and PP combination offered a feasible way to efficient utilization of alfalfa stems for bioethanol production.
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Affiliation(s)
- Xueyan Bao
- College of Animal Science, Shanxi Agricultural University, Taigu 030801, Shanxi Province, China
| | - Gang Guo
- College of Animal Science, Shanxi Agricultural University, Taigu 030801, Shanxi Province, China
| | - Wenjie Huo
- College of Animal Science, Shanxi Agricultural University, Taigu 030801, Shanxi Province, China
| | - Qinghong Li
- College of Animal Science, Shanxi Agricultural University, Taigu 030801, Shanxi Province, China
| | - Qingfang Xu
- College of Grassland Science, Shanxi Agricultural University, Taigu 030801, Shanxi Province, China
| | - Lei Chen
- College of Animal Science, Shanxi Agricultural University, Taigu 030801, Shanxi Province, China.
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Fan C, Zhang W, Guo Y, Sun K, Wang L, Luo K. Overexpression of PtoMYB115 improves lignocellulose recalcitrance to enhance biomass digestibility and bioethanol yield by specifically regulating lignin biosynthesis in transgenic poplar. BIOTECHNOLOGY FOR BIOFUELS AND BIOPRODUCTS 2022; 15:119. [PMCID: PMC9636778 DOI: 10.1186/s13068-022-02218-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/22/2022] [Accepted: 10/17/2022] [Indexed: 11/06/2022]
Abstract
Abstract
Background
Woody plants provide the most abundant biomass resource that is convertible for biofuels. Since lignin is a crucial recalcitrant factor against lignocellulose hydrolysis, genetic engineering of lignin biosynthesis is considered as a promising solution. Many MYB transcription factors have been identified to involve in the regulation of cell wall formation or phenylpropanoid pathway. In a previous study, we identified that PtoMYB115 contributes to the regulation of proanthocyanidin pathway, however, little is known about its role in lignocellulose biosynthesis and biomass saccharification in poplar.
Results
Here, we detected the changes of cell wall features and examined biomass enzymatic saccharification for bioethanol production under various chemical pretreatments in PtoMYB115 transgenic plants. We reported that PtoMYB115 might specifically regulate lignin biosynthesis to affect xylem development. Overexpression of PtoMYB115 altered lignin biosynthetic gene expression, resulting in reduced lignin deposition, raised S/G and beta-O-4 linkage, resulting in a significant reduction in cellulase adsorption with lignin and an increment in cellulose accessibility. These alterations consequently improved lignocellulose recalcitrance for significantly enhanced biomass saccharification and bioethanol yield in the PtoMYB115-OE transgenic lines. In contrast, the knockout of PtoMYB115 by CRISPR/Cas9 showed reduced woody utilization under various chemical pretreatments.
Conclusions
This study shows that PtoMYB115 plays an important role in specifically regulating lignin biosynthesis and improving lignocellulose features. The enhanced biomass saccharification and bioethanol yield in the PtoMYB115-OE lines suggests that PtoMYB115 is a candidate gene for genetic modification to facilitate the utilization of biomass.
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Jia Z, Sun M, Ou C, Sun S, Mao C, Hong L, Wang J, Li M, Jia S, Mao P. Single Seed Identification in Three Medicago Species via Multispectral Imaging Combined with Stacking Ensemble Learning. SENSORS (BASEL, SWITZERLAND) 2022; 22:s22197521. [PMID: 36236620 PMCID: PMC9572871 DOI: 10.3390/s22197521] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/06/2022] [Revised: 09/23/2022] [Accepted: 09/26/2022] [Indexed: 05/24/2023]
Abstract
Multispectral imaging (MSI) has become a new fast and non-destructive detection method in seed identification. Previous research has usually focused on single models in MSI data analysis, which always employed all features and increased the risk to efficiency and that of system cost. In this study, we developed a stacking ensemble learning (SEL) model for successfully identifying a single seed of sickle alfalfa (Medicago falcata), hybrid alfalfa (M. varia), and alfalfa (M. sativa). SEL adopted a three-layer structure, i.e., level 0 with principal component analysis (PCA), linear discriminant analysis (LDA), and quadratic discriminant analysis (QDA) as models of dimensionality reduction and feature extraction (DRFE); level 1 with support vector machine (SVM), multiple logistic regression (MLR), generalized linear models with elastic net regularization (GLMNET), and eXtreme Gradient Boosting (XGBoost) as basic learners; and level 3 with XGBoost as meta-learner. We confirmed that the values of overall accuracy, kappa, precision, sensitivity, specificity, and sensitivity in the SEL model were all significantly higher than those in basic models alone, based on both spectral features and a combination of morphological and spectral features. Furthermore, we also developed a feature filtering process and successfully selected 5 optimal features out of 33 ones, which corresponded to the contents of chlorophyll, anthocyanin, fat, and moisture in seeds. Our SEL model in MSI data analysis provided a new way for seed identification, and the feature filter process potentially could be used widely for development of a low-cost and narrow-channel sensor.
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Wu J, Wang X, Zhang R, Fu Q, Tang F, Shi F, Temuer B, Zhang Z. Comparative Transcriptome and Anatomic Characteristics of Stems in Two Alfalfa Genotypes. PLANTS (BASEL, SWITZERLAND) 2022; 11:2601. [PMID: 36235467 PMCID: PMC9570624 DOI: 10.3390/plants11192601] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/01/2022] [Revised: 09/28/2022] [Accepted: 09/30/2022] [Indexed: 06/16/2023]
Abstract
Stems are more important to forage quality than leaves in alfalfa. To understand lignin formation at different stages in alfalfa, lignin distribution, anatomical characteristics and transcriptome profile were employed using two alfalfa cultivars. The results showed that the in vitro true digestibility (IVTD) of stems in WL168 was significantly higher than that of Zhungeer, along with the significantly lower neutral detergent fiber (NDF), acid detergent fiber (ADF) and lignin contents. In addition, Zhungeer exhibited increased staining of the xylem areas in the stems of different developmental stages compared to WL168. Interestingly, the stems of WL168 appeared intracellular space from the stage 3, while Zhungeer did not. The comparative transcriptome analysis showed that a total of 1993 genes were differentially expressed in the stem between the cultivars, with a higher number of expressed genes in the stage 4. Of the differentially expressed genes, starch and sucrose metabolism as well as phenylpropanoid biosynthesis pathways were the most significantly enriched pathways. Furthermore, expression of genes involved in lignin biosynthesis such as PAL, 4CL, HCT, CAD, COMT and POD coincides with the anatomic characteristics and lignin accumulation. These results may help elucidate the regulatory mechanisms of lignin biosynthesis and improve forage quality in alfalfa.
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Affiliation(s)
- Jierui Wu
- Key Laboratory of Grassland Resources of the Ministry of Education, Technology Engineering Center of Drought and Cold-Resistant Grass Breeding in the North of the National Forestry and Grassland Administration, College of Grassland, Resources and Environment, Inner Mongolia Agricultural University, Hohhot 010010, China
| | - Xiaoyu Wang
- Key Laboratory of Grassland Resources of the Ministry of Education, Technology Engineering Center of Drought and Cold-Resistant Grass Breeding in the North of the National Forestry and Grassland Administration, College of Grassland, Resources and Environment, Inner Mongolia Agricultural University, Hohhot 010010, China
| | - Ruxue Zhang
- Key Laboratory of Grassland Resources of the Ministry of Education, Technology Engineering Center of Drought and Cold-Resistant Grass Breeding in the North of the National Forestry and Grassland Administration, College of Grassland, Resources and Environment, Inner Mongolia Agricultural University, Hohhot 010010, China
- Key Laboratory of Forage Cultivation, Processing and High Efficient Utilization of Ministry of Agriculture, Inner Mongolia Agricultural University, Hohhot 010010, China
| | - Qingwen Fu
- Key Laboratory of Grassland Resources of the Ministry of Education, Technology Engineering Center of Drought and Cold-Resistant Grass Breeding in the North of the National Forestry and Grassland Administration, College of Grassland, Resources and Environment, Inner Mongolia Agricultural University, Hohhot 010010, China
| | - Fang Tang
- Key Laboratory of Grassland Resources of the Ministry of Education, Technology Engineering Center of Drought and Cold-Resistant Grass Breeding in the North of the National Forestry and Grassland Administration, College of Grassland, Resources and Environment, Inner Mongolia Agricultural University, Hohhot 010010, China
| | - Fengling Shi
- Key Laboratory of Grassland Resources of the Ministry of Education, Technology Engineering Center of Drought and Cold-Resistant Grass Breeding in the North of the National Forestry and Grassland Administration, College of Grassland, Resources and Environment, Inner Mongolia Agricultural University, Hohhot 010010, China
| | - Buhe Temuer
- Key Laboratory of Grassland Resources of the Ministry of Education, Technology Engineering Center of Drought and Cold-Resistant Grass Breeding in the North of the National Forestry and Grassland Administration, College of Grassland, Resources and Environment, Inner Mongolia Agricultural University, Hohhot 010010, China
| | - Zhiqiang Zhang
- Key Laboratory of Grassland Resources of the Ministry of Education, Technology Engineering Center of Drought and Cold-Resistant Grass Breeding in the North of the National Forestry and Grassland Administration, College of Grassland, Resources and Environment, Inner Mongolia Agricultural University, Hohhot 010010, China
- Key Laboratory of Forage Cultivation, Processing and High Efficient Utilization of Ministry of Agriculture, Inner Mongolia Agricultural University, Hohhot 010010, China
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Cultivar Discrimination of Single Alfalfa ( Medicago sativa L.) Seed via Multispectral Imaging Combined with Multivariate Analysis. SENSORS 2020; 20:s20226575. [PMID: 33217897 PMCID: PMC7698633 DOI: 10.3390/s20226575] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/29/2020] [Revised: 11/08/2020] [Accepted: 11/13/2020] [Indexed: 12/18/2022]
Abstract
Rapid and accurate discrimination of alfalfa cultivars is crucial for producers, consumers, and market regulators. However, the conventional routine of alfalfa cultivars discrimination is time-consuming and labor-intensive. In this study, the potential of a new method was evaluated that used multispectral imaging combined with object-wise multivariate image analysis to distinguish alfalfa cultivars with a single seed. Three multivariate analysis methods including principal component analysis (PCA), linear discrimination analysis (LDA), and support vector machines (SVM) were applied to distinguish seeds of 12 alfalfa cultivars based on their morphological and spectral traits. The results showed that the combination of morphological features and spectral data could provide an exceedingly concise process to classify alfalfa seeds of different cultivars with multivariate analysis, while it failed to make the classification with only seed morphological features. Seed classification accuracy of the testing sets was 91.53% for LDA, and 93.47% for SVM. Thus, multispectral imaging combined with multivariate analysis could provide a simple, robust and nondestructive method to distinguish alfalfa seed cultivars.
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Tokunaga Y, Nagata T, Kondo K, Katahira M, Watanabe T. NMR elucidation of nonproductive binding sites of lignin models with carbohydrate-binding module of cellobiohydrolase I. BIOTECHNOLOGY FOR BIOFUELS 2020; 13:164. [PMID: 33042221 PMCID: PMC7541279 DOI: 10.1186/s13068-020-01805-w] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/24/2020] [Accepted: 09/27/2020] [Indexed: 05/30/2023]
Abstract
BACKGROUND Highly efficient enzymatic saccharification of pretreated lignocellulose is a key step in achieving lignocellulosic biorefinery. Cellobiohydrolase I (Cel7A) secreted by Trichoderma reesei is an industrially used cellulase that possesses carbohydrate-binding module 1 (TrCBM1) at the C-terminal domain. The nonproductive binding of TrCBM1 to lignin significantly decreases the enzymatic saccharification efficiency and increases the cost of biomass conversion because of the additionally required enzymes. Understanding the interaction mechanism between lignin and TrCBM1 is essential for realizing a cost-effective biofuel production; however, the binding sites in lignin have not been clearly elucidated. RESULTS Three types of 13C-labeled β-O-4 lignin oligomer models were synthesized and characterized. The 2D 1H-13C heteronuclear single-quantum correlation (HSQC) spectra of the 13C-labeled lignin models confirmed that the three types of the 13C labels were correctly incorporated in the (1) aromatic rings and β positions, (2) α positions, and (3) methoxy groups, respectively. The TrCBM1-binding sites in lignin were analyzed by observing NMR chemical shift perturbations (CSPs) using the synthetic 13C-labeled β-O-4 lignin oligomer models. Obvious CSPs were observed in signals from the aromatic regions in oligomers bound to TrCBM1, whereas perturbations in the signals from aliphatic regions and methoxy groups were insignificant. These findings indicated that hydrophobic interactions and π-π stacking were dominating factors in nonproductive binding. The synthetic lignin models have two configurations whose terminal units were differently aligned and donated C(I) and C(II). The C(I) ring showed remarkable perturbation compared with the C(II), which indicated that the binding of TrCBM1 was markedly affected by the configuration of the lignin models. The long-chain lignin models (degree of polymerization (DP) 4.16-4.70) clearly bound to TrCBM1. The interactions of TrCBM1 with the short-chain lignin models (DP 2.64-3.12) were insignificant, indicating that a DP greater than 4 was necessary for TrCBM1 binding. CONCLUSION The CSP analysis using 13C-labeled β-O-4 lignin oligomer models enabled the identification of the TrCBM1 binding sites in lignins at the atomic level. This specific interaction analysis will provide insights for new molecular designs of cellulase having a controlled affinity to cellulose and lignin for a cost-effective biorefinery process.
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Affiliation(s)
- Yuki Tokunaga
- Research Institute for Sustainable Humanosphere (RISH), Kyoto University, Uji, Kyoto 611-0011 Japan
| | - Takashi Nagata
- Institute of Advanced Energy (IAE), Kyoto University, Uji, Kyoto 611-0011 Japan
| | - Keiko Kondo
- Institute of Advanced Energy (IAE), Kyoto University, Uji, Kyoto 611-0011 Japan
| | - Masato Katahira
- Institute of Advanced Energy (IAE), Kyoto University, Uji, Kyoto 611-0011 Japan
| | - Takashi Watanabe
- Research Institute for Sustainable Humanosphere (RISH), Kyoto University, Uji, Kyoto 611-0011 Japan
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Lu C, Jing Y, Zhang H, Lee DJ, Tahir N, Zhang Q, Li W, Wang Y, Liang X, Wang J, Jin P, Zhang X. Biohydrogen production through active saccharification and photo-fermentation from alfalfa. BIORESOURCE TECHNOLOGY 2020; 304:123007. [PMID: 32070841 DOI: 10.1016/j.biortech.2020.123007] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2019] [Revised: 02/05/2020] [Accepted: 02/08/2020] [Indexed: 06/10/2023]
Abstract
Studying biohydrogen production from alfalfa is of practical significance to cleaner production and biomass utilization. The performances of biohydrogen production through active/passive saccharification and photo-fermentation were compared. The effects of initial pH, substrate concentration, and cellulase loading on biohydrogen production from alfalfa by photosynthetic bacteria HAU-M1 were presented. It was found that the maximum hydrogen yield of 55.81 mL/g was achieved at initial pH of 6.90, substrate concentration of 31.23 g/mL, and cellulase loading of 0.13 g/g. Hydrogen yield of active saccharification and photo-fermentation was much higher as compare to passive saccharification and photo-fermentation. Initial pH value showed a more significant influence on photosynthetic bacteria in comparison to cellulase in active saccharification and photo-fermentation biohydrogen production. The low yield of propionic acid suggested that it was an efficient photosynthetic hydrogen production. Photo-fermentation hydrogen production from alfalfa provides a novel path for efficient utilization of alfalfa.
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Affiliation(s)
- Chaoyang Lu
- Key Laboratory of New Materials and Facilities for Rural Renewable Energy, MOA of China, Henan Agricultural University, Zhengzhou 450002, China; Institute of Agricultural Engineering, Huanghe S & T University, Zhengzhou 450006, China
| | - Yanyan Jing
- Key Laboratory of New Materials and Facilities for Rural Renewable Energy, MOA of China, Henan Agricultural University, Zhengzhou 450002, China
| | - Huan Zhang
- Key Laboratory of New Materials and Facilities for Rural Renewable Energy, MOA of China, Henan Agricultural University, Zhengzhou 450002, China
| | - Duu-Jong Lee
- Department of Chemical Engineering, National Taiwan University, Taipei 10617, Taiwan
| | - Nadeem Tahir
- Key Laboratory of New Materials and Facilities for Rural Renewable Energy, MOA of China, Henan Agricultural University, Zhengzhou 450002, China
| | - Quanguo Zhang
- Key Laboratory of New Materials and Facilities for Rural Renewable Energy, MOA of China, Henan Agricultural University, Zhengzhou 450002, China; Institute of Agricultural Engineering, Huanghe S & T University, Zhengzhou 450006, China.
| | - Wenzhe Li
- Institute of Agricultural Engineering, Huanghe S & T University, Zhengzhou 450006, China
| | - Yi Wang
- Key Laboratory of New Materials and Facilities for Rural Renewable Energy, MOA of China, Henan Agricultural University, Zhengzhou 450002, China; Institute of Agricultural Engineering, Huanghe S & T University, Zhengzhou 450006, China
| | - Xiaoyu Liang
- Key Laboratory of New Materials and Facilities for Rural Renewable Energy, MOA of China, Henan Agricultural University, Zhengzhou 450002, China
| | - Jian Wang
- Key Laboratory of New Materials and Facilities for Rural Renewable Energy, MOA of China, Henan Agricultural University, Zhengzhou 450002, China
| | - Peng Jin
- Key Laboratory of New Materials and Facilities for Rural Renewable Energy, MOA of China, Henan Agricultural University, Zhengzhou 450002, China
| | - Xueting Zhang
- Key Laboratory of New Materials and Facilities for Rural Renewable Energy, MOA of China, Henan Agricultural University, Zhengzhou 450002, China
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Patyshakuliyeva A, Falkoski DL, Wiebenga A, Timmermans K, de Vries RP. Macroalgae Derived Fungi Have High Abilities to Degrade Algal Polymers. Microorganisms 2019; 8:E52. [PMID: 31888103 PMCID: PMC7023191 DOI: 10.3390/microorganisms8010052] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2019] [Revised: 12/13/2019] [Accepted: 12/26/2019] [Indexed: 12/21/2022] Open
Abstract
Marine fungi associated with macroalgae are an ecologically important group that have a strong potential for industrial applications. In this study, twenty-two marine fungi isolated from the brown seaweed Fucus sp. were examined for their abilities to produce algal and plant biomass degrading enzymes. Growth of these isolates on brown and green algal biomass revealed a good growth, but no preference for any specific algae. Based on the analysis of enzymatic activities, macroalgae derived fungi were able to produce algae specific and (hemi-)cellulose degrading enzymes both on algal and plant biomass. However, the production of algae specific activities was lower than the production of cellulases and xylanases. These data revealed the presence of different enzymatic approaches for the degradation of algal biomass by macroalgae derived fungi. In addition, the results of the present study indicate our poor understanding of the enzymes involved in algal biomass degradation and the mechanisms of algal carbon source utilization by marine derived fungi.
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Affiliation(s)
- Aleksandrina Patyshakuliyeva
- Fungal Physiology, Westerdijk Fungal Biodiversity Institute & Fungal Molecular Physiology, Utrecht University, Uppsalalaan 8, 3584 CT Utrecht, The Netherlands; (A.P.); (D.L.F.); (A.W.)
| | - Daniel L. Falkoski
- Fungal Physiology, Westerdijk Fungal Biodiversity Institute & Fungal Molecular Physiology, Utrecht University, Uppsalalaan 8, 3584 CT Utrecht, The Netherlands; (A.P.); (D.L.F.); (A.W.)
| | - Ad Wiebenga
- Fungal Physiology, Westerdijk Fungal Biodiversity Institute & Fungal Molecular Physiology, Utrecht University, Uppsalalaan 8, 3584 CT Utrecht, The Netherlands; (A.P.); (D.L.F.); (A.W.)
| | - Klaas Timmermans
- NIOZ Royal Netherlands Institute for Sea Research, Landsdiep 4, 1797 SZ ′t Horntje, The Netherlands;
| | - Ronald P. de Vries
- Fungal Physiology, Westerdijk Fungal Biodiversity Institute & Fungal Molecular Physiology, Utrecht University, Uppsalalaan 8, 3584 CT Utrecht, The Netherlands; (A.P.); (D.L.F.); (A.W.)
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Lei Y, Hannoufa A, Prates LL, Christensen D, Wang Y, Yu P. Silencing TT8 and HB12 Decreased Protein Degradation and Digestion, Microbial Synthesis, and Metabolic Protein in Relation to Molecular Structures of Alfalfa ( Medicago sativa). JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2019; 67:7898-7907. [PMID: 31282664 DOI: 10.1021/acs.jafc.9b02317] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
This study aimed to explore the effects of silencing HB12 and TT8 genes on protein utilization characteristics of alfalfa. Ground samples of 11 HB12-silenced (HB12i), 5 TT8-silenced (TT8i) and 4 wild type (WT) were incubated in a Daisy II incubator with N15 labeled ammonium sulfate for 0, 4, 8, 12, and 24 h. CP degradation and degradational kinetics, microbial nitrogen fractions, and protein metabolic profiles were determined. Moreover, relationships between protein profiles and FTIR spectral parameters were estimated. Results showed that transgenic alfalfa had lower CP degradation, microbial protein, and total available protein compared with WT, especially for HB12i. In addition, CP degradation and protein metabolic profiles were closely correlated with FTIR spectral parameters and thereby could be predicted from spectral parameters. In conclusion, silencing of HB12 and TT8 genes in alfalfa decreased protein degradational and metabolic profiles, which were predictable with FTIR spectral parameters.
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Affiliation(s)
- Yaogeng Lei
- Department of Animal and Poultry Science, College of Agriculture and Bioresources , University of Saskatchewan , 51 Campus Drive , Saskatoon , Saskatchewan S7N5A8 , Canada
| | - Abdelali Hannoufa
- London Research and Development Centre , Agriculture and Agri-Food Canada , 1391 Sandford Street , London , Ontario N5 V 4T3 , Canada
| | - Luciana L Prates
- Department of Animal and Poultry Science, College of Agriculture and Bioresources , University of Saskatchewan , 51 Campus Drive , Saskatoon , Saskatchewan S7N5A8 , Canada
| | - David Christensen
- Department of Animal and Poultry Science, College of Agriculture and Bioresources , University of Saskatchewan , 51 Campus Drive , Saskatoon , Saskatchewan S7N5A8 , Canada
| | - Yuxi Wang
- Lethbridge Research and Development Centre , Agriculture and Agri-Food Canada , Alberta T1J 4B1 , Canada
| | - Peiqiang Yu
- Department of Animal and Poultry Science, College of Agriculture and Bioresources , University of Saskatchewan , 51 Campus Drive , Saskatoon , Saskatchewan S7N5A8 , Canada
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Integration of renewable deep eutectic solvents with engineered biomass to achieve a closed-loop biorefinery. Proc Natl Acad Sci U S A 2019; 116:13816-13824. [PMID: 31235605 DOI: 10.1073/pnas.1904636116] [Citation(s) in RCA: 53] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Despite the enormous potential shown by recent biorefineries, the current bioeconomy still encounters multifaceted challenges. To develop a sustainable biorefinery in the future, multidisciplinary research will be essential to tackle technical difficulties. Herein, we leveraged a known plant genetic engineering approach that results in aldehyde-rich lignin via down-regulation of cinnamyl alcohol dehydrogenase (CAD) and disruption of monolignol biosynthesis. We also report on renewable deep eutectic solvents (DESs) synthesized from phenolic aldehydes that can be obtained from CAD mutant biomass. The transgenic Arabidopsis thaliana CAD mutant was pretreated with the DESs and showed a twofold increase in the yield of fermentable sugars compared with wild type (WT) upon enzymatic saccharification. Integrated use of low-recalcitrance engineered biomass, characterized by its aldehyde-type lignin subunits, in combination with a DES-based pretreatment, was found to be an effective approach for producing a high yield of sugars typically used for cellulosic biofuels and biobased chemicals. This study demonstrates that integration of renewable DES with plant genetic engineering is a promising strategy in developing a closed-loop process.
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Liu Q, Li J, Zhao J, Wu J, Shao T. Enhancement of lignocellulosic degradation in high-moisture alfalfa via anaerobic bioprocess of engineered Lactococcus lactis with the function of secreting cellulase. BIOTECHNOLOGY FOR BIOFUELS 2019; 12:88. [PMID: 31015862 PMCID: PMC6469111 DOI: 10.1186/s13068-019-1429-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/15/2018] [Accepted: 04/09/2019] [Indexed: 06/09/2023]
Abstract
BACKGROUND Butyric fermentation and a substantial loss of dry matter (DM) often occur in alfalfa silage during the rainy season, which is not conducive to subsequent biofuel production. Currently, there have been negative effects on the combination of cellulases and lactic acid bacteria (LAB) on processing high-moisture alfalfa silage; however, transgenically engineered LAB strains that secrete cellulase have been proposed as an alternative approach to avoid the above problem. The objective of the present study was to construct engineered Lactococcus lactis strains with high-efficiency secretory-expressing cellulase genes from Trichoderma reesei and to investigate the effects of the combination of transgenically engineered L. lactis strains HT1/pMG36e-usp45-bgl1, HT1/pMG36e-usp45-cbh2, and HT1/pMG36e-usp45-egl3 (HT2) on fermentation quality, structural carbohydrate degradability and nonstructural carbohydrate fermentation kinetics of high-moisture alfalfa silage treated without additive as a negative control (Control), or/and with cellulase (EN), wild-type L. lactis subsp. lactis MG1363 (HT1) and the combination of HT1 and EN (HT1 + EN) as positive additive controls. RESULTS Engineered L. lactis strains were successfully constructed and efficiently secreted endoglucanase (1118 mU/mL), cellobiohydrolase (222 mU/mL), and β-glucosidase (131 mU/mL) and had high filter paper activity (236 mU/mL). Ensiling experiments verified that HT2 obtained the highest fermentation quality score (83.6) and most efficiently processed high-moisture alfalfa silage, demonstrated by a low pH (4.49) and ammonia-N content (106 g/kg nitrogen) and a high lactic acid content (67.1 g/kg DM) and without butyric acid. Change curves of structural carbohydrates revealed that HT2 degraded more lignocelluloses, demonstrated by the lowest contents of neutral detergent fibre, acid detergent fibre, cellulose and hemicellulose after ensiling for 60 days. Kinetic analysis showed that the most residual water-soluble carbohydrates, glucose, fructose and xylose generated by lignocellulose degradation were produced by HT2, followed by HT1 + EN. The HT2-treated silages had the highest DM recovery, had the fewest Clostridia spores, emitted a fragrance and were not sticky. CONCLUSION HT2 improved the conversion of lignocellulose to sugars and processed high-moisture alfalfa silage efficiently. This is a novel strategy that can be used to enhance lignocellulosic degradation in high-moisture alfalfa via a bioprocess with transgenically engineered L. lactis strains, which could enhance the development of alfalfa as a biomass feedstock and promote second-generation biofuel development in the rainy season.
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Affiliation(s)
- Qinhua Liu
- Institute of Ensiling and Processing of Grass, Nanjing Agricultural University, Weigang 1, Nanjing, 210095 China
| | - Junfeng Li
- Institute of Ensiling and Processing of Grass, Nanjing Agricultural University, Weigang 1, Nanjing, 210095 China
| | - Jie Zhao
- Institute of Ensiling and Processing of Grass, Nanjing Agricultural University, Weigang 1, Nanjing, 210095 China
| | - Jingxing Wu
- Institute of Ensiling and Processing of Grass, Nanjing Agricultural University, Weigang 1, Nanjing, 210095 China
| | - Tao Shao
- Institute of Ensiling and Processing of Grass, Nanjing Agricultural University, Weigang 1, Nanjing, 210095 China
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Wang Z, Jönsson LJ. Comparison of catalytically non-productive adsorption of fungal proteins to lignins and pseudo-lignin using isobaric mass tagging. BIORESOURCE TECHNOLOGY 2018; 268:393-401. [PMID: 30099290 DOI: 10.1016/j.biortech.2018.07.149] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/01/2018] [Revised: 07/28/2018] [Accepted: 07/30/2018] [Indexed: 06/08/2023]
Abstract
Catalytically non-productive adsorption of fungal enzymes to pseudo-lignin (PL) was compared to adsorption to lignin preparations derived from different sources (SL, spruce; BL, birch; OL, beech) using different methods [steam pretreatment/enzymatic saccharification (SL, BL) and organosolv processing (OL)]. The protein adsorption to the SL was more extensive than the adsorption to the hardwood lignins, which was relatively similar to the adsorption to the PL. The adsorption patterns of 13 individual proteins were studied using isobaric mass tagging with TMTsixplex reagent and LC-MS/MS analysis. The results suggest that, on an average, adsorption of proteins equipped with carbohydrate-binding modules, such as the cellulases CBHI, EGII, and EGIV, was less dependent on the quality of the lignin/PL than adsorption of other proteins, such as β-Xyl, Xyn-1, and Xyn-2, which are involved in xylan degradation.
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Affiliation(s)
- Zhao Wang
- Department of Chemistry, KBC Chemical-Biological Centre, Umeå University, SE-901 87 Umeå, Sweden
| | - Leif J Jönsson
- Department of Chemistry, KBC Chemical-Biological Centre, Umeå University, SE-901 87 Umeå, Sweden.
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13
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Byrne E, Kovacs K, van Niel EWJ, Willquist K, Svensson SE, Kreuger E. Reduced use of phosphorus and water in sequential dark fermentation and anaerobic digestion of wheat straw and the application of ensiled steam-pretreated lucerne as a macronutrient provider in anaerobic digestion. BIOTECHNOLOGY FOR BIOFUELS 2018; 11:281. [PMID: 30337960 PMCID: PMC6180601 DOI: 10.1186/s13068-018-1280-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/19/2018] [Accepted: 10/04/2018] [Indexed: 05/14/2023]
Abstract
BACKGROUND Current EU directives demand increased use of renewable fuels in the transportation sector but restrict governmental support for production of biofuels produced from crops. The use of intercropped lucerne and wheat may comply with the directives. In the current study, the combination of ensiled lucerne (Medicago sativa L.) and wheat straw as substrate for hydrogen and methane production was investigated. Steam-pretreated and enzymatically hydrolysed wheat straw [WSH, 76% of total chemical oxygen demand (COD)] and ensiled lucerne (LH, 24% of total COD) were used for sequential hydrogen production through dark fermentation and methane production through anaerobic digestion and directly for anaerobic digestion. Synthetic co-cultures of extreme thermophilic Caldicellulosiruptor species adapted to elevated osmolalities were used for dark fermentation. RESULTS Based on 6 tested steam pretreatment conditions, 5 min at 200 °C was chosen for the ensiled lucerne. The same conditions as applied for wheat straw (10 min at 200 °C with 1% acetic acid) would give similar sugar yields. Volumetric hydrogen productivities of 6.7 and 4.3 mmol/L/h and hydrogen yields of 1.9 and 1.8 mol/mol hexose were observed using WSH and the combination of WSH and LH, respectively, which were relatively low compared to those of the wild-type strains. The combinations of WSH plus LH and the effluent from dark fermentation of WSH plus LH were efficiently converted to methane in anaerobic digestion with COD removal of 85-89% at organic loading rates of COD 5.4 and 8.5 g/L/day, respectively, in UASB reactors. The nutrients in the combined hydrolysates could support this conversion. CONCLUSIONS This study demonstrates the possibility of reducing the water addition to WSH by 26% and the phosphorus addition by 80% in dark fermentation with Caldicellulosiruptor species, compared to previous reports. WSH and combined WSH and LH were well tolerated by osmotolerant co-cultures. The yield was not significantly different when using defined media or hydrolysates with the same concentrations of sugars. However, the sugar concentration was negatively correlated with the hydrogen yield when comparing the results to previous reports. Hydrolysates and effluents from dark fermentation can be efficiently converted to methane. Lucerne can serve as macronutrient provider in anaerobic digestion. Intercropping with wheat is promising.
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Affiliation(s)
- Eoin Byrne
- Division of Applied Microbiology, Dept. of Chemistry, Lund University, PO Box 124, 221 00 Lund, Sweden
| | - Krisztina Kovacs
- Dept. of Chemical Engineering, Lund University, PO Box 124, 221 00 Lund, Sweden
| | - Ed W. J. van Niel
- Division of Applied Microbiology, Dept. of Chemistry, Lund University, PO Box 124, 221 00 Lund, Sweden
| | - Karin Willquist
- RISE, Forskningsbyn Ideon Scheelevägen 27, 223 70 Lund, Sweden
| | - Sven-Erik Svensson
- Dept. of Biosystems and Technology, Swedish University of Agricultural Sciences, PO Box 103, 230 53 Alnarp, Sweden
| | - Emma Kreuger
- Division of Biotechnology, Dept. of Chemistry, Lund University, PO Box 124, 221 00 Lund, Sweden
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Dier TKF, Rauber D, Durneata D, Hempelmann R, Volmer DA. Sustainable Electrochemical Depolymerization of Lignin in Reusable Ionic Liquids. Sci Rep 2017; 7:5041. [PMID: 28698638 PMCID: PMC5505966 DOI: 10.1038/s41598-017-05316-x] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2017] [Accepted: 05/26/2017] [Indexed: 11/23/2022] Open
Abstract
Lignin's aromatic building blocks provide a chemical resource that is, in theory, ideal for substitution of aromatic petrochemicals. Moreover, degradation and valorization of lignin has the potential to generate many high-value chemicals for technical applications. In this study, electrochemical degradation of alkali and Organosolv lignin was performed using the ionic liquids 1-ethyl-3-methylimidazolium trifluoromethanesulfonate and triethylammonium methanesulfonate. The extensive degradation of the investigated lignins with simultaneous almost full recovery of the electrolyte materials provided a sustainable alternative to more common lignin degradation processes. We demonstrate here that both the presence (and the absence) of water during electrolysis and proton transport reactions had significant impact on the degradation efficiency. Hydrogen peroxide radical formation promoted certain electrochemical mechanisms in electrolyte systems "contaminated" with water and increased yields of low molecular weight products significantly. The proposed mechanisms were tentatively confirmed by determining product distributions using a combination of liquid chromatography-mass spectrometry and gas-chromatography-mass spectrometry, allowing measurement of both polar versus non-polar as well as volatile versus non-volatile components in the mixtures.
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Affiliation(s)
- Tobias K F Dier
- Institute of Bioanalytical Chemistry, Saarland University, Campus B2.2, 66123, Saarbrücken, Germany
| | - Daniel Rauber
- Institute of Physical Chemistry, Saarland University, Campus B2.2, 66123, Saarbrücken, Germany
| | - Dan Durneata
- Institute of Physical Chemistry, Saarland University, Campus B2.2, 66123, Saarbrücken, Germany
| | - Rolf Hempelmann
- Institute of Physical Chemistry, Saarland University, Campus B2.2, 66123, Saarbrücken, Germany
| | - Dietrich A Volmer
- Institute of Bioanalytical Chemistry, Saarland University, Campus B2.2, 66123, Saarbrücken, Germany.
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15
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Li X, Zheng Y. Lignin-enzyme interaction: Mechanism, mitigation approach, modeling, and research prospects. Biotechnol Adv 2017; 35:466-489. [DOI: 10.1016/j.biotechadv.2017.03.010] [Citation(s) in RCA: 115] [Impact Index Per Article: 16.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2016] [Revised: 02/19/2017] [Accepted: 03/23/2017] [Indexed: 01/23/2023]
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Hojilla-Evangelista MP, Selling GW, Hatfield R, Digman M. Extraction, composition, and functional properties of dried alfalfa (Medicago sativa L.) leaf protein. JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE 2017; 97:882-888. [PMID: 27198121 DOI: 10.1002/jsfa.7810] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/22/2016] [Revised: 04/22/2016] [Accepted: 05/15/2016] [Indexed: 05/14/2023]
Abstract
BACKGROUND Alfalfa is considered a potential feedstock for biofuels; co-products with value-added uses would enhance process viability. This work evaluated dried alfalfa leaves for protein production and describes the functional properties of the protein. RESULTS Dried alfalfa leaves contained 260 g kg-1 dry basis (DB) crude protein, with albumins being the major fraction (260 g kg-1 of total protein). Alkali solubilization for 2 h at 50 °C, acid precipitation, dialysis, and freeze-drying produced a protein concentrate (600 g kg-1 DB crude protein). Alfalfa leaf protein concentrate showed moderate solubility (maximum 500 g kg-1 soluble protein from pH 5.5 to 10), excellent emulsifying properties (activity 158-219 m2 g-1 protein, stability 17-49 min) and minimal loss of solubility during heating at pH ≥ 7.0. CONCLUSIONS It is technically feasible to extract protein with desirable emulsifying and heat stability properties from dried alfalfa leaves; however, the dried form may not be a practical starting material for protein production, given the difficulty of achieving high yields and high-purity protein product. © 2016 Society of Chemical Industry.
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Affiliation(s)
- Mila P Hojilla-Evangelista
- Plant Polymer Research Unit, National Center for Agricultural Utilization Research (NCAUR), USDA Agricultural Research Service (ARS), 1815 N. University St, Peoria, IL, 61604, USA
| | - Gordon W Selling
- Plant Polymer Research Unit, National Center for Agricultural Utilization Research (NCAUR), USDA Agricultural Research Service (ARS), 1815 N. University St, Peoria, IL, 61604, USA
| | - Ronald Hatfield
- United States Dairy Forage Research Center, USDA ARS, 1925 Linden Drive West, Madison, WI, 53706, USA
| | - Matthew Digman
- United States Dairy Forage Research Center, USDA ARS, 1925 Linden Drive West, Madison, WI, 53706, USA
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17
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Dier TKF, Rauber D, Jauch J, Hempelmann R, Volmer DA. Novel Mixed-Mode Stationary Phases for Chromatographic Separation of Complex Mixtures of Decomposed Lignin. ChemistrySelect 2017. [DOI: 10.1002/slct.201601673] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Tobias K. F. Dier
- Institute of Bioanalytical Chemistry; Saarland University; 66123 Saarbrücken Germany
| | - Daniel Rauber
- Institute of Physical Chemistry; Saarland University; 66123 Saarbrücken Germany
| | - Johann Jauch
- Institute of Organic Chemistry; Saarland University; 66123 Saarbrücken Germany
| | - Rolf Hempelmann
- Institute of Physical Chemistry; Saarland University; 66123 Saarbrücken Germany
| | - Dietrich A. Volmer
- Institute of Bioanalytical Chemistry; Saarland University; 66123 Saarbrücken Germany
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18
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Harman-Ware AE, Happs RM, Davison BH, Davis MF. The effect of coumaryl alcohol incorporation on the structure and composition of lignin dehydrogenation polymers. BIOTECHNOLOGY FOR BIOFUELS 2017; 10:281. [PMID: 29213321 PMCID: PMC5707875 DOI: 10.1186/s13068-017-0962-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/05/2017] [Accepted: 11/06/2017] [Indexed: 05/14/2023]
Abstract
BACKGROUND Lignin dehydrogenation polymers (DHPs) are polymers generated from phenolic precursors for the purpose of studying lignin structure and polymerization processes. METHODS Here, DHPs were synthesized using a Zutropfverfahren method with horseradish peroxidase and three lignin monomers, sinapyl (S), coumaryl (H), and coniferyl (G) alcohols, in the presence of hydrogen peroxide. The H monomer was reacted with G and a 1:1 molar mixture of S:G monomers at H molar compositions of 0, 5, 10, and 20 mol% to study how the presence of the H monomer affected the structure and composition of the recovered polymers. RESULTS At low H concentrations, solid-state NMR spectra suggest that the H and G monomers interact to form G:H polymers that have a lower average molecular weight than the solely G-based polymer or the G:H polymer produced at higher H concentrations. Solid-state NMR and pyrolysis-MBMS analyses suggest that at higher H concentrations, the H monomer primarily self-polymerizes to produce clusters of H-based polymer that are segregated from clusters of G- or S:G-based polymers. Thioacidolysis generally showed higher recoveries of thioethylated products from S:G or S:G:H polymers made with higher H content, indicating an increase in the linear ether linkages. CONCLUSIONS Overall, the experimental results support theoretical predictions for the reactivity and structural influences of the H monomer on the formation of lignin-like polymers.
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Affiliation(s)
- Anne E. Harman-Ware
- Biosciences Center, National Renewable Energy Laboratory, 15013 Denver West Parkway, Golden, CO 80401 USA
- Bioenergy Science Center, National Renewable Energy Laboratory, 15013 Denver West Parkway, Golden, CO 80401 USA
| | - Renee M. Happs
- Biosciences Center, National Renewable Energy Laboratory, 15013 Denver West Parkway, Golden, CO 80401 USA
- Bioenergy Science Center, National Renewable Energy Laboratory, 15013 Denver West Parkway, Golden, CO 80401 USA
| | - Brian H. Davison
- Bioenergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
| | - Mark F. Davis
- Biosciences Center, National Renewable Energy Laboratory, 15013 Denver West Parkway, Golden, CO 80401 USA
- Bioenergy Science Center, National Renewable Energy Laboratory, 15013 Denver West Parkway, Golden, CO 80401 USA
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Harman-Ware AE, Foster C, Happs RM, Doeppke C, Meunier K, Gehan J, Yue F, Lu F, Davis MF. A thioacidolysis method tailored for higher-throughput quantitative analysis of lignin monomers. Biotechnol J 2016; 11:1268-1273. [PMID: 27534715 PMCID: PMC5096032 DOI: 10.1002/biot.201600266] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2016] [Revised: 08/15/2016] [Accepted: 08/17/2016] [Indexed: 11/17/2022]
Abstract
Thioacidolysis is a method used to measure the relative content of lignin monomers bound by β‐O‐4 linkages. Current thioacidolysis methods are low‐throughput as they require tedious steps for reaction product concentration prior to analysis using standard GC methods. A quantitative thioacidolysis method that is accessible with general laboratory equipment and uses a non‐chlorinated organic solvent and is tailored for higher‐throughput analysis is reported. The method utilizes lignin arylglycerol monomer standards for calibration, requires 1–2 mg of biomass per assay and has been quantified using fast‐GC techniques including a Low Thermal Mass Modular Accelerated Column Heater (LTM MACH). Cumbersome steps, including standard purification, sample concentrating and drying have been eliminated to help aid in consecutive day‐to‐day analyses needed to sustain a high sample throughput for large screening experiments without the loss of quantitation accuracy. The method reported in this manuscript has been quantitatively validated against a commonly used thioacidolysis method and across two different research sites with three common biomass varieties to represent hardwoods, softwoods, and grasses.
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Affiliation(s)
- Anne E Harman-Ware
- Bioenergy Science Center, Golden, CO, USA. .,National Bioenergy Center, National Renewable Energy Laboratory, Golden, CO, USA.
| | - Cliff Foster
- Great Lakes BioEnergy Research Center, Michigan State University, East Lansing, MI, USA
| | - Renee M Happs
- Bioenergy Science Center, Golden, CO, USA.,National Bioenergy Center, National Renewable Energy Laboratory, Golden, CO, USA
| | - Crissa Doeppke
- Bioenergy Science Center, Golden, CO, USA.,National Bioenergy Center, National Renewable Energy Laboratory, Golden, CO, USA
| | - Kristoffer Meunier
- Great Lakes BioEnergy Research Center, Michigan State University, East Lansing, MI, USA
| | - Jackson Gehan
- Great Lakes BioEnergy Research Center, Michigan State University, East Lansing, MI, USA
| | - Fengxia Yue
- Wisconsin Bioenergy Initiative, University of Wisconsin, Madison, WI, USA
| | - Fachuang Lu
- Wisconsin Bioenergy Initiative, University of Wisconsin, Madison, WI, USA
| | - Mark F Davis
- Bioenergy Science Center, Golden, CO, USA.,National Bioenergy Center, National Renewable Energy Laboratory, Golden, CO, USA
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20
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Ho-Yue-Kuang S, Alvarado C, Antelme S, Bouchet B, Cézard L, Le Bris P, Legée F, Maia-Grondard A, Yoshinaga A, Saulnier L, Guillon F, Sibout R, Lapierre C, Chateigner-Boutin AL. Mutation in Brachypodium caffeic acid O-methyltransferase 6 alters stem and grain lignins and improves straw saccharification without deteriorating grain quality. JOURNAL OF EXPERIMENTAL BOTANY 2016; 67:227-37. [PMID: 26433202 PMCID: PMC4682429 DOI: 10.1093/jxb/erv446] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
Cereal crop by-products are a promising source of renewable raw material for the production of biofuel from lignocellulose. However, their enzymatic conversion to fermentable sugars is detrimentally affected by lignins. Here the characterization of the Brachypodium Bd5139 mutant provided with a single nucleotide mutation in the caffeic acid O-methyltransferase BdCOMT6 gene is reported. This BdCOMT6-deficient mutant displayed a moderately altered lignification in mature stems. The lignin-related BdCOMT6 gene was also found to be expressed in grains, and the alterations of Bd5139 grain lignins were found to mirror nicely those evidenced in stem lignins. The Bd5139 grains displayed similar size and composition to the control. Complementation experiments carried out by introducing the mutated gene into the AtCOMT1-deficient Arabidopsis mutant demonstrated that the mutated BdCOMT6 protein was still functional. Such a moderate down-regulation of lignin-related COMT enzyme reduced the straw recalcitrance to saccharification, without compromising the vegetative or reproductive development of the plant.
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Affiliation(s)
- Séverine Ho-Yue-Kuang
- INRA-UR1268 Biopolymères, Interactions, Assemblages, F-44316 Nantes, France INRA-UMR1318, Institut Jean-Pierre Bourgin, F-78026 Versailles, France
| | - Camille Alvarado
- INRA-UR1268 Biopolymères, Interactions, Assemblages, F-44316 Nantes, France
| | - Sébastien Antelme
- INRA-UMR1318, Institut Jean-Pierre Bourgin, F-78026 Versailles, France
| | - Brigitte Bouchet
- INRA-UR1268 Biopolymères, Interactions, Assemblages, F-44316 Nantes, France
| | - Laurent Cézard
- INRA-UMR1318, Institut Jean-Pierre Bourgin, F-78026 Versailles, France
| | - Philippe Le Bris
- INRA-UMR1318, Institut Jean-Pierre Bourgin, F-78026 Versailles, France
| | - Frédéric Legée
- INRA-UMR1318, Institut Jean-Pierre Bourgin, F-78026 Versailles, France
| | | | - Arata Yoshinaga
- Laboratory of Tree Cell Biology, Division of Forest and Biomaterials Science, Graduate School of Agriculture, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan
| | - Luc Saulnier
- INRA-UR1268 Biopolymères, Interactions, Assemblages, F-44316 Nantes, France
| | - Fabienne Guillon
- INRA-UR1268 Biopolymères, Interactions, Assemblages, F-44316 Nantes, France
| | - Richard Sibout
- INRA-UMR1318, Institut Jean-Pierre Bourgin, F-78026 Versailles, France
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Wang P, Dudareva N, Morgan JA, Chapple C. Genetic manipulation of lignocellulosic biomass for bioenergy. Curr Opin Chem Biol 2015; 29:32-9. [DOI: 10.1016/j.cbpa.2015.08.006] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2015] [Revised: 08/11/2015] [Accepted: 08/12/2015] [Indexed: 11/30/2022]
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22
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Tong Z, Li H, Zhang R, Ma L, Dong J, Wang T. Co-downregulation of the hydroxycinnamoyl-CoA:shikimate hydroxycinnamoyl transferase and coumarate 3-hydroxylase significantly increases cellulose content in transgenic alfalfa (Medicago sativa L.). PLANT SCIENCE : AN INTERNATIONAL JOURNAL OF EXPERIMENTAL PLANT BIOLOGY 2015; 239:230-7. [PMID: 26398807 DOI: 10.1016/j.plantsci.2015.08.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/12/2015] [Revised: 08/06/2015] [Accepted: 08/06/2015] [Indexed: 05/04/2023]
Abstract
Lignin is a component of the cell wall that is essential for growth, development, structure and pathogen resistance in plants, but high lignin is an obstacle to the conversion of cellulose to ethanol for biofuel. Genetically modifying lignin and cellulose contents can be a good approach to overcoming that obstacle. Alfalfa (Medicago sativa L.) is rich in lignocellulose biomass and used as a model plant for the genetic modification of lignin in this study. Two key enzymes in the lignin biosynthesis pathway-hydroxycinnamoyl -CoA:shikimate hydroxycinnamoyl transferase (HCT) and coumarate 3-hydroxylase (C3H)-were co-downregulated. Compared to wild-type plants, the lignin content in the modified strain was reduced by 38%, cellulose was increased by 86.1%, enzyme saccharification efficiency was increased by 10.9%, and cell wall digestibility was increased by 13.0%. The modified alfalfa exhibited a dwarf phenotype, but normal above ground biomass. This approach provides a new strategy for reducing lignin and increasing cellulose contents and creates a new genetically modified crop with enhanced value for biofuel.
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Affiliation(s)
- Zongyong Tong
- State Key Laboratory of Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing 100193, China; Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, Beijing 100193, China.
| | - Heng Li
- State Key Laboratory of Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing 100193, China.
| | - Rongxue Zhang
- State Key Laboratory of Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing 100193, China.
| | - Lei Ma
- State Key Laboratory of Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing 100193, China.
| | - Jiangli Dong
- State Key Laboratory of Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing 100193, China.
| | - Tao Wang
- State Key Laboratory of Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing 100193, China; National Energy R&D Center for Non-food Biomass, China Agricultural University, Beijing 100193, China.
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23
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Zhou S, Runge TM. Mechanism of improved cellulosic bio-ethanol production from alfalfa stems via ambient-temperature acid pretreatment. BIORESOURCE TECHNOLOGY 2015; 193:288-296. [PMID: 26142995 DOI: 10.1016/j.biortech.2015.06.096] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/14/2015] [Revised: 06/19/2015] [Accepted: 06/20/2015] [Indexed: 06/04/2023]
Abstract
Model compounds and recalcitrant biomass were studied to elucidate the mechanism of ambient-temperature acid pretreatment of cellulosic biomass for bio-ethanol production. Pure cellulose, a pure hemicellulose and alfalfa stems were pretreated with sulfuric acid under ambient temperature with varied acid loading and time. Changes in water-soluble carbohydrates (WSCs) and chemical components of substrates were determined, and ethanol production via simultaneous saccharification and fermentation (SSF) was studied. The results showed significant amount of WSCs formed, and the WSCs increased with increasing acid loading and pretreatment time. The ethanol yields from pure cellulose were primarily affected by the added ash. Acid loading showed significant positive effect on ethanol production from alfalfa stems, whereas pretreatment time showed much weaker positive effect. However, non-significant amounts of WSCs were removed by washing of dried substrates. It was hypothesized to be because the WSCs adsorbed onto bulk substrates during the freeze-drying step, as supported by experimental results.
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Affiliation(s)
- Shengfei Zhou
- Department of Biological System Engineering, University of Wisconsin-Madison, Agricultural Engineering Building, Madison, WI 53706, USA
| | - Troy M Runge
- Department of Biological System Engineering, University of Wisconsin-Madison, Agricultural Engineering Building, Madison, WI 53706, USA.
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Analysis of a Modern Hybrid and an Ancient Sugarcane Implicates a Complex Interplay of Factors in Affecting Recalcitrance to Cellulosic Ethanol Production. PLoS One 2015; 10:e0134964. [PMID: 26252208 PMCID: PMC4529190 DOI: 10.1371/journal.pone.0134964] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2015] [Accepted: 07/15/2015] [Indexed: 11/19/2022] Open
Abstract
Abundant evidence exists to support a role for lignin as an important element in biomass recalcitrance. However, several independent studies have also shown that factors apart from lignin are also relevant and overall, the relative importance of different recalcitrance traits remains in dispute. In this study we used two genetically distant sugarcane genotypes, and performed a correlational study with the variation in anatomical parameters, cell wall composition, and recalcitrance factors between these genotypes. In addition we also tracked alterations in these characteristics in internodes at different stages of development. Significant differences in the development of the culm between the genotypes were associated with clear differential distributions of lignin content and composition that were not correlated with saccharification and fermentation yield. Given the strong influence of the environment on lignin content and composition, we hypothesized that sampling within a single plant could allow us to more easily interpret recalcitrance and changes in lignin biosynthesis than analysing variations between different genotypes with extensive changes in plant morphology and culm anatomy. The syringyl/guaiacyl (S/G) ratio was higher in the oldest internode of the modern genotype, but S/G ratio was not correlated with enzymatic hydrolysis yield nor fermentation efficiency. Curiously we observed a strong positive correlation between ferulate ester level and cellulose conversion efficiency. Together, these data support the hypothesis that biomass enzymatic hydrolysis recalcitrance is governed by a quantitative heritage rather than a single trait.
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Cass CL, Peraldi A, Dowd PF, Mottiar Y, Santoro N, Karlen SD, Bukhman YV, Foster CE, Thrower N, Bruno LC, Moskvin OV, Johnson ET, Willhoit ME, Phutane M, Ralph J, Mansfield SD, Nicholson P, Sedbrook JC. Effects of PHENYLALANINE AMMONIA LYASE (PAL) knockdown on cell wall composition, biomass digestibility, and biotic and abiotic stress responses in Brachypodium. JOURNAL OF EXPERIMENTAL BOTANY 2015; 66:4317-35. [PMID: 26093023 PMCID: PMC4493789 DOI: 10.1093/jxb/erv269] [Citation(s) in RCA: 109] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
The phenylpropanoid pathway in plants synthesizes a variety of structural and defence compounds, and is an important target in efforts to reduce cell wall lignin for improved biomass conversion to biofuels. Little is known concerning the trade-offs in grasses when perturbing the function of the first gene family in the pathway, PHENYLALANINE AMMONIA LYASE (PAL). Therefore, PAL isoforms in the model grass Brachypodium distachyon were targeted, by RNA interference (RNAi), and large reductions (up to 85%) in stem tissue transcript abundance for two of the eight putative BdPAL genes were identified. The cell walls of stems of BdPAL-knockdown plants had reductions of 43% in lignin and 57% in cell wall-bound ferulate, and a nearly 2-fold increase in the amounts of polysaccharide-derived carbohydrates released by thermochemical and hydrolytic enzymic partial digestion. PAL-knockdown plants exhibited delayed development and reduced root growth, along with increased susceptibilities to the fungal pathogens Fusarium culmorum and Magnaporthe oryzae. Surprisingly, these plants generally had wild-type (WT) resistances to caterpillar herbivory, drought, and ultraviolet light. RNA sequencing analyses revealed that the expression of genes associated with stress responses including ethylene biosynthesis and signalling were significantly altered in PAL knocked-down plants under non-challenging conditions. These data reveal that, although an attenuation of the phenylpropanoid pathway increases carbohydrate availability for biofuel, it can adversely affect plant growth and disease resistance to fungal pathogens. The data identify notable differences between the stress responses of these monocot pal mutants versus Arabidopsis (a dicot) pal mutants and provide insights into the challenges that may arise when deploying phenylpropanoid pathway-altered bioenergy crops.
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Affiliation(s)
- Cynthia L Cass
- School of Biological Sciences, Illinois State University, Normal, IL 61790 USA US Department of Energy Great Lakes Bioenergy Research Center, Madison, WI 53706, USA
| | - Antoine Peraldi
- Department of Crop Genetics, John Innes Centre, Norwich Research Park, Norwich NR4 7UH, UK
| | - Patrick F Dowd
- USDA, Agricultural Research Service, National Center for Agricultural Utilization Research, Crop Bioprotection Research Unit, Peoria, IL 61604, USA
| | - Yaseen Mottiar
- US Department of Energy Great Lakes Bioenergy Research Center, Madison, WI 53706, USA Department of Wood Science, University of British Columbia, Vancouver, V6T 1Z4, Canada
| | - Nicholas Santoro
- US Department of Energy Great Lakes Bioenergy Research Center, Michigan State University, East Lansing, MI 48824, USA
| | - Steven D Karlen
- US Department of Energy Great Lakes Bioenergy Research Center, Madison, WI 53706, USA
| | - Yury V Bukhman
- US Department of Energy Great Lakes Bioenergy Research Center, Madison, WI 53706, USA
| | - Cliff E Foster
- US Department of Energy Great Lakes Bioenergy Research Center, Michigan State University, East Lansing, MI 48824, USA
| | - Nick Thrower
- US Department of Energy Great Lakes Bioenergy Research Center, Michigan State University, East Lansing, MI 48824, USA
| | - Laura C Bruno
- Department of Crop Genetics, John Innes Centre, Norwich Research Park, Norwich NR4 7UH, UK
| | - Oleg V Moskvin
- US Department of Energy Great Lakes Bioenergy Research Center, Madison, WI 53706, USA
| | - Eric T Johnson
- USDA, Agricultural Research Service, National Center for Agricultural Utilization Research, Crop Bioprotection Research Unit, Peoria, IL 61604, USA
| | - Megan E Willhoit
- School of Biological Sciences, Illinois State University, Normal, IL 61790 USA US Department of Energy Great Lakes Bioenergy Research Center, Madison, WI 53706, USA
| | - Megha Phutane
- School of Biological Sciences, Illinois State University, Normal, IL 61790 USA US Department of Energy Great Lakes Bioenergy Research Center, Madison, WI 53706, USA
| | - John Ralph
- US Department of Energy Great Lakes Bioenergy Research Center, Madison, WI 53706, USA Department of Biochemistry, Wisconsin Energy Institute, University of Wisconsin, Madison, WI 53706, USA
| | - Shawn D Mansfield
- US Department of Energy Great Lakes Bioenergy Research Center, Madison, WI 53706, USA Department of Wood Science, University of British Columbia, Vancouver, V6T 1Z4, Canada
| | - Paul Nicholson
- Department of Crop Genetics, John Innes Centre, Norwich Research Park, Norwich NR4 7UH, UK
| | - John C Sedbrook
- School of Biological Sciences, Illinois State University, Normal, IL 61790 USA US Department of Energy Great Lakes Bioenergy Research Center, Madison, WI 53706, USA
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Zhang WJ, Wang T. Enhanced salt tolerance of alfalfa (Medicago sativa) by rstB gene transformation. PLANT SCIENCE : AN INTERNATIONAL JOURNAL OF EXPERIMENTAL PLANT BIOLOGY 2015; 234:110-8. [PMID: 25804814 DOI: 10.1016/j.plantsci.2014.11.016] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/31/2014] [Revised: 11/25/2014] [Accepted: 11/28/2014] [Indexed: 05/02/2023]
Abstract
Generating salt tolerance forage plant is essential for use of the land affected by high salinity. A salt tolerance gene rstB was used as a selectable marker gene in Agrobacterium-mediated transformation of tobacco under a selective regime of 170mM NaCl. The transgenic plants showed clear improvement in salt tolerance. To improve salt tolerance of alfalfa (Medicago sativa L.), rstB gene was introduced into alfalfa genome by Agrobacterium-mediated transformation. No abnormal phenotype was observed among the transgenic plants when compared with wild type (wt) plants. Significant enhancement of resistance to salt-shock treatment was noted on the rstB transgenic (T0) plants. Transgenic second-generation (T1) seeds showed improved germination rate and seedling growth under salt-stress condition. Hindered Na(+) accumulation, but enhanced Ca(2+) accumulation was observed on the rstB T1 plants when subjected to salt-stresses. Enhanced calcium accumulation in transgenic plants was also verified by cytohistochemical localization of calcium. Under salt-stress of 50mM NaCl, about 15% of the transgenic plants finished their life-cycle but the wt plants had no flower formation. The results demonstrated that the expression of rstB gene improved salt tolerance in transgenic alfalfa.
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Affiliation(s)
- Wan-Jun Zhang
- Department of Grassland Science, China Agricultural University, No. 2 Yuanmingyuan West Road, Haidian District, Beijing 100193, PR China.
| | - Tao Wang
- State Key Laboratory of Agro-biotechnology, China Agricultural University, 2 Yuanmingyuan West Road, Haidian District, Beijing 100193, PR China.
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Bowman MJ, Dien BS, Vermillion KE, Mertens JA. Isolation and characterization of unhydrolyzed oligosaccharides from switchgrass (Panicum virgatum, L.) xylan after exhaustive enzymatic treatment with commercial enzyme preparations. Carbohydr Res 2015; 407:42-50. [DOI: 10.1016/j.carres.2015.01.018] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2014] [Revised: 01/21/2015] [Accepted: 01/23/2015] [Indexed: 11/30/2022]
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Li Q, Song J, Peng S, Wang JP, Qu GZ, Sederoff RR, Chiang VL. Plant biotechnology for lignocellulosic biofuel production. PLANT BIOTECHNOLOGY JOURNAL 2014; 12:1174-92. [PMID: 25330253 DOI: 10.1111/pbi.12273] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/25/2014] [Revised: 08/11/2014] [Accepted: 09/05/2014] [Indexed: 05/18/2023]
Abstract
Lignocelluloses from plant cell walls are attractive resources for sustainable biofuel production. However, conversion of lignocellulose to biofuel is more expensive than other current technologies, due to the costs of chemical pretreatment and enzyme hydrolysis for cell wall deconstruction. Recalcitrance of cell walls to deconstruction has been reduced in many plant species by modifying plant cell walls through biotechnology. These results have been achieved by reducing lignin content and altering its composition and structure. Reduction of recalcitrance has also been achieved by manipulating hemicellulose biosynthesis and by overexpression of bacterial enzymes in plants to disrupt linkages in the lignin-carbohydrate complexes. These modified plants often have improved saccharification yield and higher ethanol production. Cell wall-degrading (CWD) enzymes from bacteria and fungi have been expressed at high levels in plants to increase the efficiency of saccharification compared with exogenous addition of cellulolytic enzymes. In planta expression of heat-stable CWD enzymes from bacterial thermophiles has made autohydrolysis possible. Transgenic plants can be engineered to reduce recalcitrance without any yield penalty, indicating that successful cell wall modification can be achieved without impacting cell wall integrity or plant development. A more complete understanding of cell wall formation and structure should greatly improve lignocellulosic feedstocks and reduce the cost of biofuel production.
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Affiliation(s)
- Quanzi Li
- State Key Laboratory of Tree Genetics and Breeding, Northeast Forestry University, Harbin, China; State Key Laboratory of Tree Genetics and Breeding, Chinese Academy of Forestry, Beijing, China
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Bowman MJ, Dien BS, Vermillion KE, Mertens JA. Structural characterization of (1→2)-β-xylose-(1→3)-α-arabinose-containing oligosaccharide products of extracted switchgrass (Panicum virgatum, L.) xylan after exhaustive enzymatic treatment with α-arabinofuranosidase and β-endo-xylanase. Carbohydr Res 2014; 398:63-71. [DOI: 10.1016/j.carres.2014.08.006] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2014] [Revised: 08/06/2014] [Accepted: 08/09/2014] [Indexed: 12/30/2022]
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Zhou S, Weimer PJ, Hatfield RD, Runge TM, Digman M. Improving ethanol production from alfalfa stems via ambient-temperature acid pretreatment and washing. BIORESOURCE TECHNOLOGY 2014; 170:286-292. [PMID: 25151072 DOI: 10.1016/j.biortech.2014.08.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/27/2014] [Revised: 08/01/2014] [Accepted: 08/02/2014] [Indexed: 05/27/2023]
Abstract
The concept of co-production of liquid fuel (ethanol) along with animal feed on farm was proposed, and the strategy of using ambient-temperature acid pretreatment, ensiling and washing to improve ethanol production from alfalfa stems was investigated. Alfalfa stems were separated and pretreated with sulfuric acid at ambient-temperature after harvest, and following ensiling, after which the ensiled stems were subjected to simultaneous saccharification and fermentation (SSF) for ethanol production. Ethanol yield was improved by ambient-temperature sulfuric acid pretreatment before ensiling, and by washing before SSF. It was theorized that the acid pretreatment at ambient temperature partially degraded hemicellulose, and altered cell wall structure, resulted in improved cellulose accessibility, whereas washing removed soluble ash in substrates which could inhibit the SSF. The pH of stored alfalfa stems can be used to predict the ethanol yield, with a correlation coefficient of +0.83 for washed alfalfa stems.
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Affiliation(s)
- Shengfei Zhou
- Department of Biological System Engineering, University of Wisconsin, Agricultural Engineering Building, Madison, WI 53706, USA.
| | - Paul J Weimer
- USDA-ARS, U.S. Dairy Forage Research Center, Madison, WI 53706, USA.
| | - Ronald D Hatfield
- USDA-ARS, U.S. Dairy Forage Research Center, Madison, WI 53706, USA.
| | - Troy M Runge
- Department of Biological System Engineering, University of Wisconsin, Agricultural Engineering Building, Madison, WI 53706, USA.
| | - Matthew Digman
- KUHN North America, 1501 West Seventh Avenue, Brodhead, WI 53520, USA.
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Irigoyen JJ, Goicoechea N, Antolín MC, Pascual I, Sánchez-Díaz M, Aguirreolea J, Morales F. Growth, photosynthetic acclimation and yield quality in legumes under climate change simulations: an updated survey. PLANT SCIENCE : AN INTERNATIONAL JOURNAL OF EXPERIMENTAL PLANT BIOLOGY 2014; 226:22-29. [PMID: 25113447 DOI: 10.1016/j.plantsci.2014.05.008] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/25/2013] [Revised: 05/05/2014] [Accepted: 05/17/2014] [Indexed: 06/03/2023]
Abstract
Continued emissions of CO2, derived from human activities, increase atmospheric CO2 concentration. The CO2 rise stimulates plant growth and affects yield quality. Effects of elevated CO2 on legume quality depend on interactions with N2-fixing bacteria and mycorrhizal fungi. Growth at elevated CO2 increases photosynthesis under short-term exposures in C3 species. Under long-term exposures, however, plants generally acclimate to elevated CO2 decreasing their photosynthetic capacity. An updated survey of the literature indicates that a key factor, perhaps the most important, that characteristically influences this phenomenon, its occurrence and extent, is the plant source-sink balance. In legumes, the ability of exchanging C for N at nodule level with the N2-fixing symbionts creates an extra C sink that avoids the occurrence of photosynthetic acclimation. Arbuscular mycorrhizal fungi colonizing roots may also result in increased C sink, preventing photosynthetic acclimation. Defoliation (Anthyllis vulneraria, simulated grazing) or shoot cutting (alfalfa, usual management as forage) largely increases root/shoot ratio. During re-growth at elevated CO2, new shoots growth and nodule respiration function as strong C sinks that counteracts photosynthetic acclimation. In the presence of some limiting factor, the legumes response to elevated CO2 is weakened showing photosynthetic acclimation. This survey has identified limiting factors that include an insufficient N supply from bacterial strains, nutrient-poor soils, low P supply, excess temperature affecting photosynthesis and/or nodule activity, a genetically determined low nodulation capacity, an inability of species or varieties to increase growth (and therefore C sink) at elevated CO2 and a plant phenological state or season when plant growth is stopped.
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Affiliation(s)
- J J Irigoyen
- Grupo de Fisiología del Estrés en Plantas (Dpto. de Biología Ambiental), Unidad Asociada al CSIC, EEAD, Zaragoza e ICVV, Logroño, Facultades de Ciencias y Farmacia, Universidad de Navarra, Irunlarrea 1, 31008 Pamplona, Spain
| | - N Goicoechea
- Grupo de Fisiología del Estrés en Plantas (Dpto. de Biología Ambiental), Unidad Asociada al CSIC, EEAD, Zaragoza e ICVV, Logroño, Facultades de Ciencias y Farmacia, Universidad de Navarra, Irunlarrea 1, 31008 Pamplona, Spain
| | - M C Antolín
- Grupo de Fisiología del Estrés en Plantas (Dpto. de Biología Ambiental), Unidad Asociada al CSIC, EEAD, Zaragoza e ICVV, Logroño, Facultades de Ciencias y Farmacia, Universidad de Navarra, Irunlarrea 1, 31008 Pamplona, Spain
| | - I Pascual
- Grupo de Fisiología del Estrés en Plantas (Dpto. de Biología Ambiental), Unidad Asociada al CSIC, EEAD, Zaragoza e ICVV, Logroño, Facultades de Ciencias y Farmacia, Universidad de Navarra, Irunlarrea 1, 31008 Pamplona, Spain
| | - M Sánchez-Díaz
- Grupo de Fisiología del Estrés en Plantas (Dpto. de Biología Ambiental), Unidad Asociada al CSIC, EEAD, Zaragoza e ICVV, Logroño, Facultades de Ciencias y Farmacia, Universidad de Navarra, Irunlarrea 1, 31008 Pamplona, Spain
| | - J Aguirreolea
- Grupo de Fisiología del Estrés en Plantas (Dpto. de Biología Ambiental), Unidad Asociada al CSIC, EEAD, Zaragoza e ICVV, Logroño, Facultades de Ciencias y Farmacia, Universidad de Navarra, Irunlarrea 1, 31008 Pamplona, Spain
| | - F Morales
- Estación Experimental de Aula Dei (EEAD), CSIC, Dpto. Nutrición Vegetal, Apdo. 13034, 50080 Zaragoza, Spain; Grupo de Fisiología del Estrés en Plantas (Dpto. de Biología Ambiental), Unidad Asociada al CSIC, EEAD, Zaragoza e ICVV, Logroño, Facultades de Ciencias y Farmacia, Universidad de Navarra, Irunlarrea 1, 31008 Pamplona, Spain.
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Park SH, Ong RG, Mei C, Sticklen M. Lignin down-regulation of Zea mays via dsRNAi and klason lignin analysis. J Vis Exp 2014. [PMID: 25080235 DOI: 10.3791/51340] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
To facilitate the use of lignocellulosic biomass as an alternative bioenergy resource, during biological conversion processes, a pretreatment step is needed to open up the structure of the plant cell wall, increasing the accessibility of the cell wall carbohydrates. Lignin, a polyphenolic material present in many cell wall types, is known to be a significant hindrance to enzyme access. Reduction in lignin content to a level that does not interfere with the structural integrity and defense system of the plant might be a valuable step to reduce the costs of bioethanol production. In this study, we have genetically down-regulated one of the lignin biosynthesis-related genes, cinnamoyl-CoA reductase (ZmCCR1) via a double stranded RNA interference technique. The ZmCCR1_RNAi construct was integrated into the maize genome using the particle bombardment method. Transgenic maize plants grew normally as compared to the wild-type control plants without interfering with biomass growth or defense mechanisms, with the exception of displaying of brown-coloration in transgenic plants leaf mid-ribs, husks, and stems. The microscopic analyses, in conjunction with the histological assay, revealed that the leaf sclerenchyma fibers were thinned but the structure and size of other major vascular system components was not altered. The lignin content in the transgenic maize was reduced by 7-8.7%, the crystalline cellulose content was increased in response to lignin reduction, and hemicelluloses remained unchanged. The analyses may indicate that carbon flow might have been shifted from lignin biosynthesis to cellulose biosynthesis. This article delineates the procedures used to down-regulate the lignin content in maize via RNAi technology, and the cell wall compositional analyses used to verify the effect of the modifications on the cell wall structure.
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Affiliation(s)
| | - Rebecca Garlock Ong
- Department of Chemical Engineering and Materials Science, DOE Great Lakes Bioenergy Research Center, Michigan State University
| | - Chuansheng Mei
- The Institute for Sustainable and Renewable Resources, The Institute for Advanced Learning and Research
| | - Mariam Sticklen
- Department of Plant, Soil and Microbial Sciences, Michigan State University
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Guo F, Shi W, Sun W, Li X, Wang F, Zhao J, Qu Y. Differences in the adsorption of enzymes onto lignins from diverse types of lignocellulosic biomass and the underlying mechanism. BIOTECHNOLOGY FOR BIOFUELS 2014; 7:38. [PMID: 24624960 PMCID: PMC3995585 DOI: 10.1186/1754-6834-7-38] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/18/2014] [Accepted: 03/04/2014] [Indexed: 05/02/2023]
Abstract
BACKGROUND Non-productive cellulase adsorption onto lignin has always been deemed to negatively affect the enzymatic hydrolysis of lignocellulosic feedstocks. Therefore, understanding enzyme-lignin interactions is essential for the development of enzyme mixtures, the processes of lignocellulose hydrolysis, and the genetic modification of lignocellulosic biomass and enzymes. In this work, we examined the properties of six lignins from diverse types of lignocellulosic biomass (aspen, pine, corn stover, kenaf, and two Arabidopsis lines, wild-type and SALK mutant of fah1) to determine the mechanism of differences in their adsorption of enzymes. RESULTS We found that lignin sources affected enzyme adsorption using structural features, such as functional groups and lignin composition. Guaiacyl (G) lignin had a higher adsorption capacity on enzymes than syringyl (S) lignin. The low S/G ratio and high uniform lignin fragment size had good correlations with high adsorption capacity. A higher content of phenolic hydroxyl groups and a lower content of carboxylic acid groups resulted in stronger adsorption affinity for corn stover lignin (CL) than for kenaf lignin (KL) and aspen lignin (AL). The lower amount of aliphatic hydroxyls that reduced hydrophobic interactions could explain the higher adsorption capacity of pine lignin (PL) than CL. Enzyme activity assays, as well as the hydrolysis of Avicel, phosphoric acid-swollen cellulose (PASC), and holocellulose, were performed to study the behaviors of mono-component enzymes that resulted in adsorption. We found that cellobiohydrolase (CBH) and xylanase were adsorbed the most by all lignins, endoglucanase (EG) showed less inhibition, and β-glucosidase (BG) was the least affected by lignins, indicating the important role of carbohydrate-binding module (CBM) in protein adsorption. CONCLUSION Lignin sources affect enzyme adsorption using structural features and lignin composition, such as S/G ratio, carboxylic acid, aliphatic hydroxyl, and phenolic hydroxyl. For mono-component enzymes, the adsorption capacity decreased in the order CBH, xylanase > EG > BG. These investigations revealed the difference in lignin properties between diverse biomass and adsorption capacity of enzymes to lignins, and the possible underlying mechanism. The results can also serve as a reference for the genetic modification of lignocellulosic biomass and enzymes.
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Affiliation(s)
- Fenfen Guo
- State Key Laboratory of Microbial Technology, Shandong University, Ji-nan City, Shandong Province 250100, China
| | - Wenjing Shi
- State Key Laboratory of Microbial Technology, Shandong University, Ji-nan City, Shandong Province 250100, China
| | - Wan Sun
- State Key Laboratory of Microbial Technology, Shandong University, Ji-nan City, Shandong Province 250100, China
| | - Xuezhi Li
- State Key Laboratory of Microbial Technology, Shandong University, Ji-nan City, Shandong Province 250100, China
| | - Feifei Wang
- State Key Laboratory of Microbial Technology, Shandong University, Ji-nan City, Shandong Province 250100, China
| | - Jian Zhao
- State Key Laboratory of Microbial Technology, Shandong University, Ji-nan City, Shandong Province 250100, China
| | - Yinbo Qu
- State Key Laboratory of Microbial Technology, Shandong University, Ji-nan City, Shandong Province 250100, China
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Dien BS, O'Bryan PJ, Hector RE, Iten LB, Mitchell RB, Qureshi N, Sarath G, Vogel KP, Cotta MA. Conversion of switchgrass to ethanol using dilute ammonium hydroxide pretreatment: influence of ecotype and harvest maturity. ENVIRONMENTAL TECHNOLOGY 2013; 34:1837-1848. [PMID: 24350437 DOI: 10.1080/09593330.2013.833640] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Switchgrass (Panicum virgatum L.) is a perennial C4 grass that is being developed as a bioenergy crop because it has high production yields and suitable agronomic traits. Five switchgrass biomass samples from upland and lowland switchgrass ecotypes harvested at different stages or maturity were used in this study. Switchgrass samples contained 317.0-385.0 g glucans/kg switchgrass dry basis (db) and 579.3-660.2 g total structural carbohydrates/kg switchgrass, db. Carbohydrate contents were greater for the upland ecotype versus lowland ecotype and increased with harvest maturity. Pretreatment of switchgrass with dilute ammonium hydroxide (8% w/w ammonium loading) at 170 degrees C for 20 min was determined to be effective for preparing switchgrass for enzymatic conversion to monosaccharides; glucose recoveries were 66.9-90.5% and xylose recoveries 60.1-84.2% of maximum and decreased with increased maturity at harvest. Subsequently, pretreated switchgrass samples were converted to ethanol by simultaneous saccharification and fermentation using engineered xylose-fermenting Saccharomyces cerevisiae strain YRH400. Ethanol yields were 176.2-202.01/Mg of switchgrass (db) and followed a similar trend as observed for enzymatic sugar yields.
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Affiliation(s)
- Bruce S Dien
- Bioenergy Research Unit, National Center for Agricultural Utilization Research, USDA, Agricultural Research Service, 1815 N. University Street, Peoria, IL 61604-3902, USA.
| | - Patricia J O'Bryan
- Bioenergy Research Unit, National Center for Agricultural Utilization Research, USDA, Agricultural Research Service, 1815 N. University Street, Peoria, IL 61604-3902, USA
| | - Ronald E Hector
- Bioenergy Research Unit, National Center for Agricultural Utilization Research, USDA, Agricultural Research Service, 1815 N. University Street, Peoria, IL 61604-3902, USA
| | - Loren B Iten
- Bioenergy Research Unit, National Center for Agricultural Utilization Research, USDA, Agricultural Research Service, 1815 N. University Street, Peoria, IL 61604-3902, USA
| | - Robert B Mitchell
- Grain, Forage, and Bioenergy Research Unit, University of Nebraska, 137 Keim Hall, Box 830937, Lincoln, NE 68583-0937, USA
| | - Nasib Qureshi
- Bioenergy Research Unit, National Center for Agricultural Utilization Research, USDA, Agricultural Research Service, 1815 N. University Street, Peoria, IL 61604-3902, USA
| | - Gautum Sarath
- Grain, Forage, and Bioenergy Research Unit, University of Nebraska, 137 Keim Hall, Box 830937, Lincoln, NE 68583-0937, USA
| | - Kenneth P Vogel
- Grain, Forage, and Bioenergy Research Unit, University of Nebraska, 137 Keim Hall, Box 830937, Lincoln, NE 68583-0937, USA
| | - Michael A Cotta
- Bioenergy Research Unit, National Center for Agricultural Utilization Research, USDA, Agricultural Research Service, 1815 N. University Street, Peoria, IL 61604-3902, USA
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35
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Gea G, Kjell S, Jean-François H. Integrated -omics: a powerful approach to understanding the heterogeneous lignification of fibre crops. Int J Mol Sci 2013; 14:10958-78. [PMID: 23708098 PMCID: PMC3709712 DOI: 10.3390/ijms140610958] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2013] [Revised: 05/15/2013] [Accepted: 05/17/2013] [Indexed: 12/15/2022] Open
Abstract
Lignin and cellulose represent the two main components of plant secondary walls and the most abundant polymers on Earth. Quantitatively one of the principal products of the phenylpropanoid pathway, lignin confers high mechanical strength and hydrophobicity to plant walls, thus enabling erect growth and high-pressure water transport in the vessels. Lignin is characterized by a high natural heterogeneity in its composition and abundance in plant secondary cell walls, even in the different tissues of the same plant. A typical example is the stem of fibre crops, which shows a lignified core enveloped by a cellulosic, lignin-poor cortex. Despite the great value of fibre crops for humanity, however, still little is known on the mechanisms controlling their cell wall biogenesis, and particularly, what regulates their spatially-defined lignification pattern. Given the chemical complexity and the heterogeneous composition of fibre crops' secondary walls, only the use of multidisciplinary approaches can convey an integrated picture and provide exhaustive information covering different levels of biological complexity. The present review highlights the importance of combining high throughput -omics approaches to get a complete understanding of the factors regulating the lignification heterogeneity typical of fibre crops.
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Affiliation(s)
- Guerriero Gea
- Department Environment and Agro-biotechnologies (EVA), Centre de Recherche Public-Gabriel Lippmann, 41, Rue du Brill, L-4422 Belvaux, Luxembourg; E-Mails: (G.G.); (S.K.)
| | - Sergeant Kjell
- Department Environment and Agro-biotechnologies (EVA), Centre de Recherche Public-Gabriel Lippmann, 41, Rue du Brill, L-4422 Belvaux, Luxembourg; E-Mails: (G.G.); (S.K.)
| | - Hausman Jean-François
- Department Environment and Agro-biotechnologies (EVA), Centre de Recherche Public-Gabriel Lippmann, 41, Rue du Brill, L-4422 Belvaux, Luxembourg; E-Mails: (G.G.); (S.K.)
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36
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Van Acker R, Vanholme R, Storme V, Mortimer JC, Dupree P, Boerjan W. Lignin biosynthesis perturbations affect secondary cell wall composition and saccharification yield in Arabidopsis thaliana. BIOTECHNOLOGY FOR BIOFUELS 2013; 6:46. [PMID: 23622268 PMCID: PMC3661393 DOI: 10.1186/1754-6834-6-46] [Citation(s) in RCA: 187] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/27/2012] [Accepted: 03/26/2013] [Indexed: 05/02/2023]
Abstract
BACKGROUND Second-generation biofuels are generally produced from the polysaccharides in the lignocellulosic plant biomass, mainly cellulose. However, because cellulose is embedded in a matrix of other polysaccharides and lignin, its hydrolysis into the fermentable glucose is hampered. The senesced inflorescence stems of a set of 20 Arabidopsis thaliana mutants in 10 different genes of the lignin biosynthetic pathway were analyzed for cell wall composition and saccharification yield. Saccharification models were built to elucidate which cell wall parameters played a role in cell wall recalcitrance. RESULTS Although lignin is a key polymer providing the strength necessary for the plant's ability to grow upward, a reduction in lignin content down to 64% of the wild-type level in Arabidopsis was tolerated without any obvious growth penalty. In contrast to common perception, we found that a reduction in lignin was not compensated for by an increase in cellulose, but rather by an increase in matrix polysaccharides. In most lignin mutants, the saccharification yield was improved by up to 88% cellulose conversion for the cinnamoyl-coenzyme A reductase1 mutants under pretreatment conditions, whereas the wild-type cellulose conversion only reached 18%. The saccharification models and Pearson correlation matrix revealed that the lignin content was the main factor determining the saccharification yield. However, also lignin composition, matrix polysaccharide content and composition, and, especially, the xylose, galactose, and arabinose contents influenced the saccharification yield. Strikingly, cellulose content did not significantly affect saccharification yield. CONCLUSIONS Although the lignin content had the main effect on saccharification, also other cell wall factors could be engineered to potentially increase the cell wall processability, such as the galactose content. Our results contribute to a better understanding of the effect of lignin perturbations on plant cell wall composition and its influence on saccharification yield, and provide new potential targets for genetic improvement.
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Affiliation(s)
- Rebecca Van Acker
- Department of Plant Systems Biology, VIB, Technologiepark 927, Gent, 9052, Belgium
- Department of Plant Biotechnology and Bioinformatics, Ghent University, Gent, 9052, Belgium
| | - Ruben Vanholme
- Department of Plant Systems Biology, VIB, Technologiepark 927, Gent, 9052, Belgium
- Department of Plant Biotechnology and Bioinformatics, Ghent University, Gent, 9052, Belgium
| | - Véronique Storme
- Department of Plant Systems Biology, VIB, Technologiepark 927, Gent, 9052, Belgium
- Department of Plant Biotechnology and Bioinformatics, Ghent University, Gent, 9052, Belgium
| | - Jennifer C Mortimer
- Department of Biochemistry, Cambridge University, Cambridge, CB2 1QW, United Kingdom
| | - Paul Dupree
- Department of Biochemistry, Cambridge University, Cambridge, CB2 1QW, United Kingdom
| | - Wout Boerjan
- Department of Plant Systems Biology, VIB, Technologiepark 927, Gent, 9052, Belgium
- Department of Plant Biotechnology and Bioinformatics, Ghent University, Gent, 9052, Belgium
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37
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Fiasconaro ML, Gogorcena Y, Muñoz F, Andueza D, Sánchez-Díaz M, Antolín MC. Effects of nitrogen source and water availability on stem carbohydrates and cellulosic bioethanol traits of alfalfa plants. PLANT SCIENCE : AN INTERNATIONAL JOURNAL OF EXPERIMENTAL PLANT BIOLOGY 2012; 191-192:16-23. [PMID: 22682561 DOI: 10.1016/j.plantsci.2012.04.007] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/27/2012] [Revised: 04/16/2012] [Accepted: 04/18/2012] [Indexed: 06/01/2023]
Abstract
Symbiotic association of legumes with rhizobia frequently results in higher photosynthesis and soluble carbohydrates in comparison with nitrate-fed plants, which might improve its potential for biomass conversion into bioethanol. A greenhouse experiment was conducted to examine the effects of nitrogen source and water availability on stem characteristics and on relationships between carbohydrates, phenolic metabolism activity and cell wall composition in alfalfa (Medicago sativa L. cv. Aragón). The experiment included three treatments: (1) plants fed with ammonium nitrate (AN); (2) plants inoculated with rhizobia (R); and (3) plants inoculated with rhizobia and amended with sewage sludge (RS). Two levels of irrigation were imposed: (1) well-watered and (2) drought stress. Under well-watered conditions, nitrogen-fixing plants have increased photosynthesis and stem fermentable carbohydrate concentrations, which result in higher potential for biomass conversion to bioethanol than in AN plants. The latter had higher lignin due to enhanced activities of phenolic metabolism-related enzymes. Under drought conditions, the potential for bioethanol conversion decreased to a similar level in all treatments. Drought-stressed nitrogen-fixing plants have high concentrations of fermentable carbohydrates and cell wall cellulose, but ammonium nitrate-fed plants produced higher plant and stem biomass, which might compensate the decreasing stem carbohydrates and cellulose concentrations.
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Affiliation(s)
- M Laura Fiasconaro
- Dpto. Biología Vegetal, Sección Biología Vegetal, Unidad Asociada al CSIC-EEAD, Zaragoza, ICVV, Logroño, Facultades de Ciencias y Farmacia, Universidad de Navarra, C/Irunlarrea 1, 31008 Pamplona, Spain
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38
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Eudes A, George A, Mukerjee P, Kim JS, Pollet B, Benke PI, Yang F, Mitra P, Sun L, Cetinkol OP, Chabout S, Mouille G, Soubigou-Taconnat L, Balzergue S, Singh S, Holmes BM, Mukhopadhyay A, Keasling JD, Simmons BA, Lapierre C, Ralph J, Loqué D. Biosynthesis and incorporation of side-chain-truncated lignin monomers to reduce lignin polymerization and enhance saccharification. PLANT BIOTECHNOLOGY JOURNAL 2012; 10:609-20. [PMID: 22458713 DOI: 10.1111/j.1467-7652.2012.00692.x] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Lignocellulosic biomass is utilized as a renewable feedstock in various agro-industrial activities. Lignin is an aromatic, hydrophobic and mildly branched polymer integrally associated with polysaccharides within the biomass, which negatively affects their extraction and hydrolysis during industrial processing. Engineering the monomer composition of lignins offers an attractive option towards new lignins with reduced recalcitrance. The presented work describes a new strategy developed in Arabidopsis for the overproduction of rare lignin monomers to reduce lignin polymerization degree (DP). Biosynthesis of these 'DP reducers' is achieved by expressing a bacterial hydroxycinnamoyl-CoA hydratase-lyase (HCHL) in lignifying tissues of Arabidopsis inflorescence stems. HCHL cleaves the propanoid side-chain of hydroxycinnamoyl-CoA lignin precursors to produce the corresponding hydroxybenzaldehydes so that plant stems expressing HCHL accumulate in their cell wall higher amounts of hydroxybenzaldehyde and hydroxybenzoate derivatives. Engineered plants with intermediate HCHL activity levels show no reduction in total lignin, sugar content or biomass yield compared with wild-type plants. However, cell wall characterization of extract-free stems by thioacidolysis and by 2D-NMR revealed an increased amount of unusual C₆C₁ lignin monomers most likely linked with lignin as end-groups. Moreover the analysis of lignin isolated from these plants using size-exclusion chromatography revealed a reduced molecular weight. Furthermore, these engineered lines show saccharification improvement of pretreated stem cell walls. Therefore, we conclude that enhancing the biosynthesis and incorporation of C₆C₁ monomers ('DP reducers') into lignin polymers represents a promising strategy to reduce lignin DP and to decrease cell wall recalcitrance to enzymatic hydrolysis.
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Affiliation(s)
- Aymerick Eudes
- Joint BioEnergy Institute, EmeryStation East, Emeryville, CA, USA
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Bowman MJ, Dien BS, Hector RE, Sarath G, Cotta MA. Liquid chromatography-mass spectrometry investigation of enzyme-resistant xylooligosaccharide structures of switchgrass associated with ammonia pretreatment, enzymatic saccharification, and fermentation. BIORESOURCE TECHNOLOGY 2012; 110:437-47. [PMID: 22330596 DOI: 10.1016/j.biortech.2012.01.062] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/08/2011] [Revised: 01/03/2012] [Accepted: 01/13/2012] [Indexed: 05/11/2023]
Abstract
Switchgrass is a potential source of renewable biomass for conversion to liquid biofuels. Efficient conversion requires effective strategies for pretreatment and enzymatic saccharification to produce fermentable sugars. Standard analysis of fermentation liquids includes detection of monosaccharides and ethanol to determine efficiency of conversion. Larger components, specifically oligosaccharides, are typically not measured due to the structural complexity of the products; however, as oligosaccharides they represent carbon available in biomass that is not converted to liquid fuels. In this study, ammonia-pretreated switchgrass was enzymatically depolymerized either independently or under simultaneous saccharification and fermentation conditions. Residual oligosaccharides were reducing end-labeled followed by hydrophilic interaction liquid chromatography mass spectrometry/mass spectrometry analysis. These data reveal 20 oligosaccharide peaks with distinct retention times and tandem mass spectrometry fragmentation patterns representing 13 different oligosaccharide compositions. All measured compositions were smaller than a chain length of six and were neither linear xylooligosaccharides nor modified with phenolic esters. This work represents a robust method to monitor and identify unhydrolyzed oligosaccharides from fermentations, thereby permitting the screening of targeted enzymatic activities to promote the complete hydrolysis of xylan.
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Affiliation(s)
- Michael J Bowman
- USDA, Agricultural Research Service, National Center for Agricultural Utilization Research, Bioenergy Research Unit, 1815 N. University Street, Peoria, IL 61604, USA.
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