Anode-assisted electro-fermentation with Bacillus subtilis under oxygen-limited conditions

Yu Sun, Marika Kokko, Igor Vassilev

Research output: Contribution to journalArticleScientificpeer-review

3 Citations (Scopus)
8 Downloads (Pure)

Abstract

Background: Bacillus subtilis is generally regarded as a ubiquitous facultative anaerobe. Oxygen is the major electron acceptor of B. subtilis, and when oxygen is absent, B. subtilis can donate electrons to nitrate or perform fermentation. An anode electrode can also be used by microorganisms as the electron sink in systems called anodic electro-fermentation. The facultative anaerobic character of B. subtilis makes it an excellent candidate to explore with different electron acceptors, such as an anode. This study aimed to optimise industrial aerobic bioprocesses using alternative electron acceptors. In particular, different end product spectrum of B. subtilis with various electron acceptors, including anode from the electro-fermentation system, was investigated. Results: B. subtilis was grown using three electron acceptors, i.e. oxygen, nitrate and anode (poised at a potential of 0.7 V vs. standard hydrogen electrode). The results showed oxygen had a crucial role for cells to remain metabolically active. When nitrate or anode was applied as the sole electron acceptor anaerobically, immediate cell lysis and limited glucose consumption were observed. In anode-assisted electro-fermentation with a limited aeration rate, acetoin, as the main end product showed the highest yield of 0.78 ± 0.04 molproduct/molglucose, two-fold higher than without poised potential (0.39 ± 0.08 molproduct/molglucose). Conclusions: Oxygen controls B. subtilis biomass growth, alternative electron acceptors utilisation and metabolites formation. Limited oxygen/air supply enabled the bacteria to donate excess electrons to nitrate or anode, leading to steered product spectrum. The anode-assisted electro-fermentation showed its potential to boost acetoin production for future industrial biotechnology applications.

Original languageEnglish
Number of pages12
JournalBiotechnology for Biofuels and Bioproducts
Volume16
Issue number6
DOIs
Publication statusPublished - Jan 2023
Publication typeA1 Journal article-refereed

Keywords

  • Acetoin bioproduction
  • Anode respiration
  • Anode-assisted electro-fermentation
  • Bacillus subtilis
  • Oxygen supply

Publication forum classification

  • Publication forum level 2

ASJC Scopus subject areas

  • Biotechnology
  • Renewable Energy, Sustainability and the Environment
  • Applied Microbiology and Biotechnology
  • Energy (miscellaneous)
  • Management, Monitoring, Policy and Law

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