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A synthetic consortium of Klebsiella pneumoniae and Shewanella oneidensis is engineered to efficiently harvest electricity from glycerol in microbial fuel cells.

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What they did

System
MFC

What worked

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Abstract

Microbial fuel cell (MFC) is an eco‐friendly bio‐electrochemical sys­tem that uses microorganism as biocatalyst to convert biomass into electricity. Glycerol, as a waste in the biodiesel refinery processes, is an appealing substrate for MFC. Nevertheless, glycerol cannot be utilized as carbon source by well‐known exoelectrogens such as Shewanella oneidensis . Herein, to generate electricity by rapidly harnessing glycerol, the authors rationally constructed a Klebsiella pneumoniae ‐ Shewanella oneidensis microbial consortium to efficiently harvest electricity from glyc­erol, in which K. pneumoniae converted glycerol into lactate, fed to S. oneidensis as carbon source and electron donor. To improve electricity output, the authors systematically engineered the consortium in terms of carbon flux distribution and efficiency of extracellular electron transfer (EET). To direct more carbon flux to lactate biosynthesis in K. pneumoniae , the authors eliminated the ethanol pathway by knocking out the alcohol dehydrogenase gene ( adhE ), and enhanced lactate biosynthesis by heterologously expressing a lactate dehydrogen­ase gene ( ldhD ) from Lactobacillus bulgaricus and a lactate transporter gene ( lldP ) from Escherichia coli . To facilitate EET between S. oneidensis and anode surfaces, a biosynthetic flavins pathway from Bacillus subtilis is introduced into S. oneidensis . The author further optimized the glycerol concentration, thus S. oneidensis could be continuously fed with lactate synthesized from K. pneumoniae at a constant rate. Our glycerol‐fed MFC generated a maximum power density of 19.9 mW/m 2 , significantly higher than that of the wild‐type consor­tium. This work suggested that engineering microbial consortia is an effi­cient strategy to expand the spectrum of usable carbon sources and promote electricity power production in MFCs.

Key findings

  • Glycerol cannot be utilized as a carbon source by Shewanella oneidensis, but can be converted to lactate by Klebsiella pneumoniae.
  • The consortium is engineered to direct more carbon flux to lactate biosynthesis in Klebsiella pneumoniae.
  • Elimination of the ethanol pathway in Klebsiella pneumoniae improves electricity output in the microbial fuel cell.

Keywords

Shewanella oneidensisMicrobial fuel cellGlycerolShewanellaMicrobial consortiumKlebsiella pneumoniae

Identifiers

DOI
10.1002/biot.201700491
Journal
Biotechnology Journal
Year
2017