Base-Catalyzed Depolymerization of Solid Lignin-Rich Streams Enables Microbial Conversion

Alberto Rodriguez, Davinia Salvachúa, Rui Katahira, Brenna A. Black, Nicholas S. Cleveland, Michelle Reed, Holly Smith, Edward E.K. Baidoo, Jay D. Keasling, Blake A. Simmons, Gregg T. Beckham, John M. Gladden

Research output: Contribution to journalArticlepeer-review

113 Scopus Citations

Abstract

Lignin valorization offers significant potential to enhance the economic viability of lignocellulosic biorefineries. However, because of its heterogeneous and recalcitrant nature, conversion of lignin to value-added coproducts remains a considerable technical challenge. In this study, we employ base-catalyzed depolymerization (BCD) using a process-relevant solid lignin stream produced via deacetylation, mechanical refining, and enzymatic hydrolysis to enable biological lignin conversion. BCD was conducted with the solid lignin substrate over a range of temperatures at two NaOH concentrations, and the results demonstrate that the lignin can be partially extracted and saponified at temperatures as low as 60 °C. At 120 °C and 2% NaOH, the high extent of lignin solubility was accompanied by a considerable decrease in the lignin average molecular weight and the release of lignin-derived monomers including hydroxycinnamic acids. BCD liquors were tested for microbial growth using seven aromatic-catabolizing bacteria and two yeasts. Three organisms (Pseudomonas putida KT2440, Rhodotorula mucilaginosa, and Corynebacterium glutamicum) tolerate high BCD liquor concentrations (up to 90% v/v) and rapidly consume the main lignin-derived monomers, resulting in lignin conversion of up to 15%. Furthermore, as a proof of concept, muconic acid production from a representative lignin BCD liquor was demonstrated with an engineered P. putida KT2440 strain. These results highlight the potential for a mild lignin depolymerization process to enhance the microbial conversion of solid lignin-rich biorefinery streams.

Original languageAmerican English
Pages (from-to)8171-8180
Number of pages10
JournalACS Sustainable Chemistry and Engineering
Volume5
Issue number9
DOIs
StatePublished - 5 Sep 2017

Bibliographical note

Publisher Copyright:
© 2017 American Chemical Society.

NREL Publication Number

  • NREL/JA-5100-70189

Keywords

  • Base-catalyzed depolymerization
  • Biological conversion
  • Lignin liquor
  • Lignin monomers
  • Muconic acid

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