Use of the lignocellulose-degrading bacterium Caldicellulosiruptor bescii to assess recalcitrance and conversion of wild-type and transgenic poplar
Abstract Background Biological conversion of lignocellulosic biomass is significantly hindered by feedstock recalcitrance, which is typically assessed through an enzymatic digestion assay, often preceded by a thermal and/or chemical pretreatment. Here, we assay 17 lines of unpretreated transgenic bl...
| Main Authors: | , , , , , |
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| Format: | Article |
| Language: | English |
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BMC
2020-03-01
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| Series: | Biotechnology for Biofuels |
| Subjects: | |
| Online Access: | http://link.springer.com/article/10.1186/s13068-020-01675-2 |
| _version_ | 1818547453057564672 |
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| author | Christopher T. Straub Ryan G. Bing Jack P. Wang Vincent L. Chiang Michael W. W. Adams Robert M. Kelly |
| author_facet | Christopher T. Straub Ryan G. Bing Jack P. Wang Vincent L. Chiang Michael W. W. Adams Robert M. Kelly |
| author_sort | Christopher T. Straub |
| collection | DOAJ |
| description | Abstract Background Biological conversion of lignocellulosic biomass is significantly hindered by feedstock recalcitrance, which is typically assessed through an enzymatic digestion assay, often preceded by a thermal and/or chemical pretreatment. Here, we assay 17 lines of unpretreated transgenic black cottonwood (Populus trichocarpa) utilizing a lignocellulose-degrading, metabolically engineered bacterium, Caldicellulosiruptor bescii. The poplar lines were assessed by incubation with an engineered C. bescii strain that solubilized and converted the hexose and pentose carbohydrates to ethanol and acetate. The resulting fermentation titer and biomass solubilization were then utilized as a measure of biomass recalcitrance and compared to data previously reported on the transgenic poplar samples. Results Of the 17 transgenic poplar lines examined with C. bescii, a wide variation in solubilization and fermentation titer was observed. While the wild type poplar control demonstrated relatively high recalcitrance with a total solubilization of only 20% and a fermentation titer of 7.3 mM, the transgenic lines resulted in solubilization ranging from 15 to 79% and fermentation titers from 6.8 to 29.6 mM. Additionally, a strong inverse correlation (R 2 = 0.8) between conversion efficiency and lignin content was observed with lower lignin samples more easily converted and solubilized by C. bescii. Conclusions Feedstock recalcitrance can be significantly reduced with transgenic plants, but finding the correct modification may require a large sample set to identify the most advantageous genetic modifications for the feedstock. Utilizing C. bescii as a screening assay for recalcitrance, poplar lines with down-regulation of coumarate 3-hydroxylase 3 (C3H3) resulted in the highest degrees of solubilization and conversion by C. bescii. One such line, with a growth phenotype similar to the wild-type, generated more than three times the fermentation products of the wild-type poplar control, suggesting that excellent digestibility can be achieved without compromising fitness of the tree. |
| first_indexed | 2024-12-12T08:06:55Z |
| format | Article |
| id | doaj.art-def592aa44ec467eb8fecef76292f1e0 |
| institution | Directory Open Access Journal |
| issn | 1754-6834 |
| language | English |
| last_indexed | 2024-12-12T08:06:55Z |
| publishDate | 2020-03-01 |
| publisher | BMC |
| record_format | Article |
| series | Biotechnology for Biofuels |
| spelling | doaj.art-def592aa44ec467eb8fecef76292f1e02022-12-22T00:31:56ZengBMCBiotechnology for Biofuels1754-68342020-03-0113111010.1186/s13068-020-01675-2Use of the lignocellulose-degrading bacterium Caldicellulosiruptor bescii to assess recalcitrance and conversion of wild-type and transgenic poplarChristopher T. Straub0Ryan G. Bing1Jack P. Wang2Vincent L. Chiang3Michael W. W. Adams4Robert M. Kelly5Department of Chemical and Biomolecular Engineering, North Carolina State UniversityDepartment of Chemical and Biomolecular Engineering, North Carolina State UniversityDepartment of Forestry and Environmental Resources, North Carolina State UniversityDepartment of Forestry and Environmental Resources, North Carolina State UniversityDepartment of Biochemistry and Molecular Biology, University of GeorgiaDepartment of Chemical and Biomolecular Engineering, North Carolina State UniversityAbstract Background Biological conversion of lignocellulosic biomass is significantly hindered by feedstock recalcitrance, which is typically assessed through an enzymatic digestion assay, often preceded by a thermal and/or chemical pretreatment. Here, we assay 17 lines of unpretreated transgenic black cottonwood (Populus trichocarpa) utilizing a lignocellulose-degrading, metabolically engineered bacterium, Caldicellulosiruptor bescii. The poplar lines were assessed by incubation with an engineered C. bescii strain that solubilized and converted the hexose and pentose carbohydrates to ethanol and acetate. The resulting fermentation titer and biomass solubilization were then utilized as a measure of biomass recalcitrance and compared to data previously reported on the transgenic poplar samples. Results Of the 17 transgenic poplar lines examined with C. bescii, a wide variation in solubilization and fermentation titer was observed. While the wild type poplar control demonstrated relatively high recalcitrance with a total solubilization of only 20% and a fermentation titer of 7.3 mM, the transgenic lines resulted in solubilization ranging from 15 to 79% and fermentation titers from 6.8 to 29.6 mM. Additionally, a strong inverse correlation (R 2 = 0.8) between conversion efficiency and lignin content was observed with lower lignin samples more easily converted and solubilized by C. bescii. Conclusions Feedstock recalcitrance can be significantly reduced with transgenic plants, but finding the correct modification may require a large sample set to identify the most advantageous genetic modifications for the feedstock. Utilizing C. bescii as a screening assay for recalcitrance, poplar lines with down-regulation of coumarate 3-hydroxylase 3 (C3H3) resulted in the highest degrees of solubilization and conversion by C. bescii. One such line, with a growth phenotype similar to the wild-type, generated more than three times the fermentation products of the wild-type poplar control, suggesting that excellent digestibility can be achieved without compromising fitness of the tree.http://link.springer.com/article/10.1186/s13068-020-01675-2CaldicellulosiruptorExtreme thermophilesLignocelluloseBiofuelPoplar |
| spellingShingle | Christopher T. Straub Ryan G. Bing Jack P. Wang Vincent L. Chiang Michael W. W. Adams Robert M. Kelly Use of the lignocellulose-degrading bacterium Caldicellulosiruptor bescii to assess recalcitrance and conversion of wild-type and transgenic poplar Biotechnology for Biofuels Caldicellulosiruptor Extreme thermophiles Lignocellulose Biofuel Poplar |
| title | Use of the lignocellulose-degrading bacterium Caldicellulosiruptor bescii to assess recalcitrance and conversion of wild-type and transgenic poplar |
| title_full | Use of the lignocellulose-degrading bacterium Caldicellulosiruptor bescii to assess recalcitrance and conversion of wild-type and transgenic poplar |
| title_fullStr | Use of the lignocellulose-degrading bacterium Caldicellulosiruptor bescii to assess recalcitrance and conversion of wild-type and transgenic poplar |
| title_full_unstemmed | Use of the lignocellulose-degrading bacterium Caldicellulosiruptor bescii to assess recalcitrance and conversion of wild-type and transgenic poplar |
| title_short | Use of the lignocellulose-degrading bacterium Caldicellulosiruptor bescii to assess recalcitrance and conversion of wild-type and transgenic poplar |
| title_sort | use of the lignocellulose degrading bacterium caldicellulosiruptor bescii to assess recalcitrance and conversion of wild type and transgenic poplar |
| topic | Caldicellulosiruptor Extreme thermophiles Lignocellulose Biofuel Poplar |
| url | http://link.springer.com/article/10.1186/s13068-020-01675-2 |
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