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Effective alkaline metal-catalyzed oxidative delignification of hybrid poplar

BACKGROUND: Strategies to improve copper-catalyzed alkaline hydrogen peroxide (Cu-AHP) pretreatment of hybrid poplar were investigated. These improvements included a combination of increasing hydrolysis yields, while simultaneously decreasing process inputs through (i) more efficient utilization of...

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Autores principales: Bhalla, Aditya, Bansal, Namita, Stoklosa, Ryan J., Fountain, Mackenzie, Ralph, John, Hodge, David B., Hegg, Eric L.
Formato: Online Artículo Texto
Lenguaje:English
Publicado: BioMed Central 2016
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4746924/
https://www.ncbi.nlm.nih.gov/pubmed/26862348
http://dx.doi.org/10.1186/s13068-016-0442-0
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author Bhalla, Aditya
Bansal, Namita
Stoklosa, Ryan J.
Fountain, Mackenzie
Ralph, John
Hodge, David B.
Hegg, Eric L.
author_facet Bhalla, Aditya
Bansal, Namita
Stoklosa, Ryan J.
Fountain, Mackenzie
Ralph, John
Hodge, David B.
Hegg, Eric L.
author_sort Bhalla, Aditya
collection PubMed
description BACKGROUND: Strategies to improve copper-catalyzed alkaline hydrogen peroxide (Cu-AHP) pretreatment of hybrid poplar were investigated. These improvements included a combination of increasing hydrolysis yields, while simultaneously decreasing process inputs through (i) more efficient utilization of H(2)O(2) and (ii) the addition of an alkaline extraction step prior to the metal-catalyzed AHP pretreatment. We hypothesized that utilizing this improved process could substantially lower the chemical inputs needed during pretreatment. RESULTS: Hybrid poplar was pretreated utilizing a modified process in which an alkaline extraction step was incorporated prior to the Cu-AHP treatment step and H(2)O(2) was added batch-wise over the course of 10 h. Our results revealed that the alkaline pre-extraction step improved both lignin and xylan solubilization, which ultimately led to improved glucose (86 %) and xylose (95 %) yields following enzymatic hydrolysis. An increase in the lignin solubilization was also observed with fed-batch H(2)O(2) addition relative to batch-only addition, which again resulted in increased glucose and xylose yields (77 and 93 % versus 63 and 74 %, respectively). Importantly, combining these strategies led to significantly improved sugar yields (96 % glucose and 94 % xylose) following enzymatic hydrolysis. In addition, we found that we could substantially lower the chemical inputs (enzyme, H(2)O(2), and catalyst), while still maintaining high product yields utilizing the improved Cu-AHP process. This pretreatment also provided a relatively pure lignin stream consisting of ≥90 % Klason lignin and only 3 % xylan and 2 % ash following precipitation. Two-dimensional heteronuclear single-quantum coherence (2D HSQC) NMR and size-exclusion chromatography demonstrated that the solubilized lignin was high molecular weight (M(w) ≈ 22,000 Da) and only slightly oxidized relative to lignin from untreated poplar. CONCLUSIONS: This study demonstrated that the fed-batch, two-stage Cu-AHP pretreatment process was effective in pretreating hybrid poplar for its conversion into fermentable sugars. Results showed sugar yields near the theoretical maximum were achieved from enzymatically hydrolyzed hybrid poplar by incorporating an alkaline extraction step prior to pretreatment and by efficiently utilizing H(2)O(2) during the Cu-AHP process. Significantly, this study reports high sugar yields from woody biomass treated with an AHP pretreatment under mild reaction conditions. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s13068-016-0442-0) contains supplementary material, which is available to authorized users.
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spelling pubmed-47469242016-02-10 Effective alkaline metal-catalyzed oxidative delignification of hybrid poplar Bhalla, Aditya Bansal, Namita Stoklosa, Ryan J. Fountain, Mackenzie Ralph, John Hodge, David B. Hegg, Eric L. Biotechnol Biofuels Research BACKGROUND: Strategies to improve copper-catalyzed alkaline hydrogen peroxide (Cu-AHP) pretreatment of hybrid poplar were investigated. These improvements included a combination of increasing hydrolysis yields, while simultaneously decreasing process inputs through (i) more efficient utilization of H(2)O(2) and (ii) the addition of an alkaline extraction step prior to the metal-catalyzed AHP pretreatment. We hypothesized that utilizing this improved process could substantially lower the chemical inputs needed during pretreatment. RESULTS: Hybrid poplar was pretreated utilizing a modified process in which an alkaline extraction step was incorporated prior to the Cu-AHP treatment step and H(2)O(2) was added batch-wise over the course of 10 h. Our results revealed that the alkaline pre-extraction step improved both lignin and xylan solubilization, which ultimately led to improved glucose (86 %) and xylose (95 %) yields following enzymatic hydrolysis. An increase in the lignin solubilization was also observed with fed-batch H(2)O(2) addition relative to batch-only addition, which again resulted in increased glucose and xylose yields (77 and 93 % versus 63 and 74 %, respectively). Importantly, combining these strategies led to significantly improved sugar yields (96 % glucose and 94 % xylose) following enzymatic hydrolysis. In addition, we found that we could substantially lower the chemical inputs (enzyme, H(2)O(2), and catalyst), while still maintaining high product yields utilizing the improved Cu-AHP process. This pretreatment also provided a relatively pure lignin stream consisting of ≥90 % Klason lignin and only 3 % xylan and 2 % ash following precipitation. Two-dimensional heteronuclear single-quantum coherence (2D HSQC) NMR and size-exclusion chromatography demonstrated that the solubilized lignin was high molecular weight (M(w) ≈ 22,000 Da) and only slightly oxidized relative to lignin from untreated poplar. CONCLUSIONS: This study demonstrated that the fed-batch, two-stage Cu-AHP pretreatment process was effective in pretreating hybrid poplar for its conversion into fermentable sugars. Results showed sugar yields near the theoretical maximum were achieved from enzymatically hydrolyzed hybrid poplar by incorporating an alkaline extraction step prior to pretreatment and by efficiently utilizing H(2)O(2) during the Cu-AHP process. Significantly, this study reports high sugar yields from woody biomass treated with an AHP pretreatment under mild reaction conditions. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s13068-016-0442-0) contains supplementary material, which is available to authorized users. BioMed Central 2016-02-09 /pmc/articles/PMC4746924/ /pubmed/26862348 http://dx.doi.org/10.1186/s13068-016-0442-0 Text en © Bhalla et al. 2016 Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.
spellingShingle Research
Bhalla, Aditya
Bansal, Namita
Stoklosa, Ryan J.
Fountain, Mackenzie
Ralph, John
Hodge, David B.
Hegg, Eric L.
Effective alkaline metal-catalyzed oxidative delignification of hybrid poplar
title Effective alkaline metal-catalyzed oxidative delignification of hybrid poplar
title_full Effective alkaline metal-catalyzed oxidative delignification of hybrid poplar
title_fullStr Effective alkaline metal-catalyzed oxidative delignification of hybrid poplar
title_full_unstemmed Effective alkaline metal-catalyzed oxidative delignification of hybrid poplar
title_short Effective alkaline metal-catalyzed oxidative delignification of hybrid poplar
title_sort effective alkaline metal-catalyzed oxidative delignification of hybrid poplar
topic Research
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4746924/
https://www.ncbi.nlm.nih.gov/pubmed/26862348
http://dx.doi.org/10.1186/s13068-016-0442-0
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