Fractionation and characterization of lignin streams from unique high-lignin content endocarp feedstocks

Abstract Background Lignin is a promising source of building blocks for upgrading to valuable aromatic chemicals and materials. Endocarp biomass represents a non-edible crop residue in an existing agricultural setting which cannot be used as animal feed nor soil amendment. With significantly higher...

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Main Authors: Wenqi Li, Kirtley Amos, Mi Li, Yunqiao Pu, Seth Debolt, Arthur J. Ragauskas, Jian Shi
Format: Article
Language:English
Published: BMC 2018-11-01
Series:Biotechnology for Biofuels
Subjects:
Online Access:http://link.springer.com/article/10.1186/s13068-018-1305-7
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spelling doaj-9fad3238b7254d618d2f4d07d60a69dc2020-11-25T01:34:03ZengBMCBiotechnology for Biofuels1754-68342018-11-0111111410.1186/s13068-018-1305-7Fractionation and characterization of lignin streams from unique high-lignin content endocarp feedstocksWenqi Li0Kirtley Amos1Mi Li2Yunqiao Pu3Seth Debolt4Arthur J. Ragauskas5Jian Shi6Biosystems and Agricultural Engineering, University of KentuckyDepartment of Horticulture, University of KentuckyJoint Institute of Biological Science, Biosciences Division, Oak Ridge National LaboratoryJoint Institute of Biological Science, Biosciences Division, Oak Ridge National LaboratoryDepartment of Horticulture, University of KentuckyJoint Institute of Biological Science, Biosciences Division, Oak Ridge National LaboratoryBiosystems and Agricultural Engineering, University of KentuckyAbstract Background Lignin is a promising source of building blocks for upgrading to valuable aromatic chemicals and materials. Endocarp biomass represents a non-edible crop residue in an existing agricultural setting which cannot be used as animal feed nor soil amendment. With significantly higher lignin content and bulk energy density, endocarps have significant advantages to be converted into both biofuel and bioproducts as compared to other biomass resources. Deep eutectic solvent (DES) is highly effective in fractionating lignin from a variety of biomass feedstocks with high yield and purity while at lower cost comparing to certain ionic liquids. Results In the present study, the structural and compositional features of peach and walnut endocarp cells were characterized. Compared to typical woody and herbaceous biomass, endocarp biomass exhibits significantly higher bulk density and hardness due to its high cellular density. The sugar yields of DES (1:2 choline chloride: lactic acid) pretreated peach pit (Prunus persica) and walnut shell (Juglans nigra) were determined and the impacts of DES pretreatment on the physical and chemical properties of extracted lignin were characterized. Enzymatic saccharification of DES pretreated walnut and peach endocarps gave high glucose yields (over 90%); meanwhile, compared with dilute acid and alkaline pretreatment, DES pretreatment led to significantly higher lignin removal (64.3% and 70.2% for walnut and peach endocarps, respectively). The molecular weights of the extracted lignin from DES pretreated endocarp biomass were significantly reduced. 1H–13C HSQC NMR results demonstrate that the native endocarp lignins were SGH type lignins with dominant G-unit (86.7% and 80.5% for walnut and peach endocarps lignins, respectively). DES pretreatment decreased the S and H-unit while led to an increase in condensed G-units, which may contribute to a higher thermal stability of the isolated lignin. Nearly all β-O-4′ and a large portion of β-5′ linkages were removed during DES pretreatment. Conclusions The high lignin content endocarps have unique cell wall characteristics when compared to the other lignocellulosic biomass feedstocks. DES pretreatment was highly effective in fractionating high lignin content endocarps to produce both sugar and lignin streams while the DES extracted lignins underwent significant changes in SGH ratio, interunit linkages, and molecular sizes.http://link.springer.com/article/10.1186/s13068-018-1305-7EndocarpDeep eutectic solventPretreatmentLigninBiofuelBiorefinery
collection DOAJ
language English
format Article
sources DOAJ
author Wenqi Li
Kirtley Amos
Mi Li
Yunqiao Pu
Seth Debolt
Arthur J. Ragauskas
Jian Shi
spellingShingle Wenqi Li
Kirtley Amos
Mi Li
Yunqiao Pu
Seth Debolt
Arthur J. Ragauskas
Jian Shi
Fractionation and characterization of lignin streams from unique high-lignin content endocarp feedstocks
Biotechnology for Biofuels
Endocarp
Deep eutectic solvent
Pretreatment
Lignin
Biofuel
Biorefinery
author_facet Wenqi Li
Kirtley Amos
Mi Li
Yunqiao Pu
Seth Debolt
Arthur J. Ragauskas
Jian Shi
author_sort Wenqi Li
title Fractionation and characterization of lignin streams from unique high-lignin content endocarp feedstocks
title_short Fractionation and characterization of lignin streams from unique high-lignin content endocarp feedstocks
title_full Fractionation and characterization of lignin streams from unique high-lignin content endocarp feedstocks
title_fullStr Fractionation and characterization of lignin streams from unique high-lignin content endocarp feedstocks
title_full_unstemmed Fractionation and characterization of lignin streams from unique high-lignin content endocarp feedstocks
title_sort fractionation and characterization of lignin streams from unique high-lignin content endocarp feedstocks
publisher BMC
series Biotechnology for Biofuels
issn 1754-6834
publishDate 2018-11-01
description Abstract Background Lignin is a promising source of building blocks for upgrading to valuable aromatic chemicals and materials. Endocarp biomass represents a non-edible crop residue in an existing agricultural setting which cannot be used as animal feed nor soil amendment. With significantly higher lignin content and bulk energy density, endocarps have significant advantages to be converted into both biofuel and bioproducts as compared to other biomass resources. Deep eutectic solvent (DES) is highly effective in fractionating lignin from a variety of biomass feedstocks with high yield and purity while at lower cost comparing to certain ionic liquids. Results In the present study, the structural and compositional features of peach and walnut endocarp cells were characterized. Compared to typical woody and herbaceous biomass, endocarp biomass exhibits significantly higher bulk density and hardness due to its high cellular density. The sugar yields of DES (1:2 choline chloride: lactic acid) pretreated peach pit (Prunus persica) and walnut shell (Juglans nigra) were determined and the impacts of DES pretreatment on the physical and chemical properties of extracted lignin were characterized. Enzymatic saccharification of DES pretreated walnut and peach endocarps gave high glucose yields (over 90%); meanwhile, compared with dilute acid and alkaline pretreatment, DES pretreatment led to significantly higher lignin removal (64.3% and 70.2% for walnut and peach endocarps, respectively). The molecular weights of the extracted lignin from DES pretreated endocarp biomass were significantly reduced. 1H–13C HSQC NMR results demonstrate that the native endocarp lignins were SGH type lignins with dominant G-unit (86.7% and 80.5% for walnut and peach endocarps lignins, respectively). DES pretreatment decreased the S and H-unit while led to an increase in condensed G-units, which may contribute to a higher thermal stability of the isolated lignin. Nearly all β-O-4′ and a large portion of β-5′ linkages were removed during DES pretreatment. Conclusions The high lignin content endocarps have unique cell wall characteristics when compared to the other lignocellulosic biomass feedstocks. DES pretreatment was highly effective in fractionating high lignin content endocarps to produce both sugar and lignin streams while the DES extracted lignins underwent significant changes in SGH ratio, interunit linkages, and molecular sizes.
topic Endocarp
Deep eutectic solvent
Pretreatment
Lignin
Biofuel
Biorefinery
url http://link.springer.com/article/10.1186/s13068-018-1305-7
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