Biomass augmentation through thermochemical pretreatments greatly enhances digestion of switchgrass by Clostridium thermocellum

Kothari, Ninad; Holwerda, Evert K.; Cai, Charles M.; Kumar, Rajeev; Wyman, Charles E.

doi:10.1186/s13068-018-1216-7

Title: Biomass augmentation through thermochemical pretreatments greatly enhances digestion of switchgrass by Clostridium thermocellum

Journal Article · Sat Aug 04 00:00:00 EDT 2018 · Biotechnology for Biofuels

DOI:https://doi.org/10.1186/s13068-018-1216-7· OSTI ID:1626995

Kothari, Ninad ^[1]; Holwerda, Evert K. ^[2]; Cai, Charles M. ^[3]; Kumar, Rajeev ^[4];

^[5]

Univ. of California, Riverside, CA (United States). Bourns College of Engineering. Dept. of Chemical and Environmental Engineering; Univ. of California, Riverside, CA (United States). Bourns College of Engineering. Center for Environmental Research and Technology (CE-CERT); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). BioEnergy Science Center (BESC)
Dartmouth College, Hanover, NH (United States). Thayer School of Engineering; Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). BioEnergy Science Center (BESC)
Univ. of California, Riverside, CA (United States). Bourns College of Engineering. Dept. of Chemical and Environmental Engineering; Univ. of California, Riverside, CA (United States). Bourns College of Engineering. Center for Environmental Research and Technology (CE-CERT); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Center for Bioenergy Innovation (CBI)
Univ. of California, Riverside, CA (United States). Bourns College of Engineering. Center for Environmental Research and Technology (CE-CERT); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). BioEnergy Science Center (BESC); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Center for Bioenergy Innovation (CBI)
Univ. of California, Riverside, CA (United States). Bourns College of Engineering. Dept. of Chemical and Environmental Engineering; Univ. of California, Riverside, CA (United States). Bourns College of Engineering. Center for Environmental Research and Technology (CE-CERT); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). BioEnergy Science Center (BESC); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Center for Bioenergy Innovation (CBI)

Background: The thermophilic anaerobic bacterium Clostridium thermocellum is a multifunctional ethanol producer, capable of both saccharifcation and fermentation, that is central to the consolidated bioprocessing (CBP) approach of converting lignocellulosic biomass to ethanol without external enzyme supplementation. Although CBP organisms have evolved efcient machinery for biomass deconstruction, achieving complete solubilization requires targeted approaches, such as pretreatment, to prepare recalcitrant biomass feedstocks for further biological digestion. Here, diferences between how C. thermocellum and fungal cellulases respond to senescent switchgrass prepared by four diferent pretreatment techniques revealed relationships between biomass substrate composition and its digestion by the two biological approaches. Results: Alamo switchgrass was pretreated using hydrothermal, dilute acid, dilute alkali, and co-solvent-enhanced lignocellulosic fractionation (CELF) pretreatments to produce solids with varying glucan, xylan, and lignin compositions. C. thermocellum achieved highest sugar release and metabolite production from de-lignifed switchgrass prepared by CELF and dilute alkali pretreatments demonstrating greater resilience to the presence of hemicellulose sugars than fungal enzymes. 100% glucan solubilization and glucan plus xylan release from switchgrass were achieved using the CELF–CBP combination. Lower glucan solubilization and metabolite production by C. thermocellum was observed on solids prepared by dilute acid and hydrothermal pretreatments with higher xylan removal from switchgrass than lignin removal. Further, C. thermocellum (2% by volume inoculum) showed ~48% glucan solubilization compared to <10% through fungal enzymatic hydrolysis (15 and 65 mg protein/g glucan loadings) of unpretreated switchgrass indicating the efectiveness of C. thermocellum’s cellulosome. Overall, C. thermocellum performed equivalent to 65 and better than 15 mg protein/g glucan fungal enzymatic hydrolysis on all substrates except CELFpretreated substrates. CELF pretreatments of switchgrass produced solids that were highly digestible regardless of whether C. thermocellum or fungal enzymes were chosen. Conclusions: The unparalleled comprehensive nature of this work with a comparison of four pretreatment and two biological digestion techniques provides a strong platform for future integration of pretreatment with CBP. Lignin removal had a more positive impact on biological digestion of switchgrass than xylan removal from the biomass. However, the impact of switchgrass structural properties, including cellulose, hemicellulose, and lignin characterization, would provide a better understanding of lignocellulose deconstruction.

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Research Organization:: Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)

Sponsoring Organization:: USDOE Office of Science (SC)

Grant/Contract Number:: AC05-00OR22725

OSTI ID:: 1626995

Journal Information:: Biotechnology for Biofuels, Vol. 11, Issue 1; ISSN 1754-6834

Publisher:: BioMed CentralCopyright Statement

Country of Publication:: United States

Language:: English

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Lignocellulose solubilization and conversion by extremely thermophilic Caldicellulosiruptor bescii improves by maintaining metabolic activity Straub, Christopher T.; Khatibi, Piyum A.; Otten, Jonathan K. Biotechnology and Bioengineering, Vol. 116, Issue 8 https://doi.org/10.1002/bit.26993	journal	May 2019
Cellulose hydrolysis by Clostridium thermocellum is agnostic to substrate structural properties in contrast to fungal cellulases Kothari, Ninad; Bhagia, Samarthya; Zaher, Maher Green Chemistry, Vol. 21, Issue 10 https://doi.org/10.1039/c9gc00262f	journal	January 2019

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09 BIOMASS FUELS
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Biomass augmentation through thermochemical pretreatments greatly enhances digestion of switchgrass by Clostridium thermocellum Kothari, Ninad; Holwerda, Evert; Cai, Charles https://doi.org/10.6084/m9.figshare.c.4189061 The current record is supplemented by this collection	collection	January 2018
MOESM2 of Biomass augmentation through thermochemical pretreatments greatly enhances digestion of switchgrass by Clostridium thermocellum Kothari, Ninad; Holwerda, Evert; Cai, Charles https://doi.org/10.6084/m9.figshare.6934397 The current record is supplemented by this text	text	January 2018
MOESM1 of Biomass augmentation through thermochemical pretreatments greatly enhances digestion of switchgrass by Clostridium thermocellum Kothari, Ninad; Holwerda, Evert; Cai, Charles https://doi.org/10.6084/m9.figshare.6934391 The current record is supplemented by this text	text	January 2018
MOESM2 of Biomass augmentation through thermochemical pretreatments greatly enhances digestion of switchgrass by Clostridium thermocellum Kothari, Ninad; Holwerda, Evert; Cai, Charles https://doi.org/10.6084/m9.figshare.6934397.v1 The current record is supplemented by this text	text	January 2018
Biomass augmentation through thermochemical pretreatments greatly enhances digestion of switchgrass by Clostridium thermocellum Kothari, Ninad; Holwerda, Evert; Cai, Charles https://doi.org/10.6084/m9.figshare.c.4189061.v1 The current record is supplemented by this collection	collection	January 2018
MOESM1 of Biomass augmentation through thermochemical pretreatments greatly enhances digestion of switchgrass by Clostridium thermocellum Kothari, Ninad; Holwerda, Evert; Cai, Charles https://doi.org/10.6084/m9.figshare.6934391.v1 The current record is supplemented by this text	text	January 2018