Integration of renewable deep eutectic solvents with engineered biomass to achieve a closed-loop biorefinery

Kwang Ho Kim, Aymerick Eudes, Keunhong Jeong, Chang Geun Yoo, Chang Soo Kim, and Arthur Ragauskas
PNAS July 9, 2019 116 (28) 13816-13824; first published June 24, 2019 https://doi.org/10.1073/pnas.1904636116

  1. Edited by Alexis T. Bell, University of California, Berkeley, CA, and approved June 3, 2019 (received for review March 17, 2019)

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Significance

Deep eutectic solvents (DESs) have gained increasing attention due to their application-friendly properties, including universal solvating capabilities and wide tunability. Additionally, ease of synthesis and broad availability from inexpensive chemical components could render DESs more versatile solvents for biomass pretreatment, as compared with traditional ionic liquids. Because the long-term success of the biorefinery depends on the development of sustainable processes to convert lignocellulosics into biofuels, DESs derived from renewable sources such as lignin are highly desirable. We herein present our innovative process that integrates the use of low-recalcitrant engineered biomass with its pretreatment using lignin-derived DESs. The promising results described by near-theoretical sugar yield demonstrate the effectiveness of the integrated process, opening up opportunities toward a sustainable and circular bioeconomy.

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.

Footnotes

  • ↵1To whom correspondence may be addressed. Email: kwanghokim{at}kist.re.kr.

  • Author contributions: K.H.K. and A.E. designed research; K.H.K., A.E., K.J., and C.G.Y. performed research; K.H.K., K.J., C.G.Y., C.S.K., and A.R. analyzed data; and K.H.K., A.E., K.J., C.G.Y., C.S.K., and A.R. wrote the paper.

  • The authors declare no conflict of interest.

  • This article is a PNAS Direct Submission.

  • This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1904636116/-/DCSupplemental.

Published under the PNAS license.

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Integration of renewable deep eutectic solvents with engineered biomass to achieve a closed-loop biorefinery
Kwang Ho Kim, Aymerick Eudes, Keunhong Jeong, Chang Geun Yoo, Chang Soo Kim, Arthur Ragauskas
Proceedings of the National Academy of Sciences Jul 2019, 116 (28) 13816-13824; DOI: 10.1073/pnas.1904636116
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