Thermochemical Wastewater Valorization via Enhanced Microbial Toxicity Tolerance

Gregg Beckham, Christopher Johnson, Brenna Pleitner, Nicholas Cleveland, William Michener, Jessica Olstad-Thompson, Derek Vardon, Jason Whitham, Richard Giannone, Dawn Klingeman, Robert Brown, Steven Brown, Robert Hettich, Adam Guss

Research output: Contribution to journalArticlepeer-review

71 Scopus Citations


Thermochemical (TC) biomass conversion processes such as pyrolysis and liquefaction generate considerable amounts of wastewater, which often contains highly toxic compounds that are incredibly challenging to convert via standard wastewater treatment approaches such as anaerobic digestion. These streams represent a cost for TC biorefineries, and a potential valorization opportunity, if effective conversion methods are developed. The primary challenge hindering microbial conversion of TC wastewater is toxicity. In this study, we employ a robust bacterium, Pseudomonas putida, with TC wastewater streams to demonstrate that aldehydes are the most inhibitory compounds in these streams. Proteomics, transcriptomics, and fluorescence-based immunoassays of P. putida grown in a representative wastewater stream indicate that stress results from protein damage, which we hypothesize is a primary toxicity mechanism. Constitutive overexpression of the chaperone genes, groEL, groES, and clpB, in a genome-reduced P. putida strain improves the tolerance towards multiple TC wastewater samples up to 200-fold. Moreover, the concentration ranges of TC wastewater are industrially relevant for further bioprocess development for all wastewater streams examined here, representing different TC process configurations. Furthermore, we demonstrate proof-of-concept polyhydroxyalkanoate production from the usable carbon in an exemplary TC wastewater stream. Overall, this study demonstrates that protein quality control machinery and repair mechanisms can enable substantial gains in microbial tolerance to highly toxic substrates, including heterogeneous waste streams. When coupled to other metabolic engineering advances such as expanded substrate utilization and enhanced product accumulation, this study generally enables new strategies for biological conversion of highly-toxic, organic-rich wastewater via engineered aerobic monocultures or designer consortia.

Original languageAmerican English
Pages (from-to)1625-1638
Number of pages14
JournalEnergy and Environmental Science
Issue number6
StatePublished - Jun 2018

Bibliographical note

Publisher Copyright:
© 2018 The Royal Society of Chemistry.

NREL Publication Number

  • NREL/JA-2A00-71485


  • thermochemical biomass conversion
  • toxicity
  • wastewater


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