Superior anodic electro-fermentation by enhancing capacity for extracellular electron transfer

Liuyan Gu; Xinxin Xiao; Sang Yup Lee; Bin Lai; Christian Solem

doi:10.1016/j.biortech.2023.129813

Superior anodic electro-fermentation by enhancing capacity for extracellular electron transfer

Bioresour Technol. 2023 Dec:389:129813. doi: 10.1016/j.biortech.2023.129813. Epub 2023 Sep 28.

Authors

Liuyan Gu¹, Xinxin Xiao², Sang Yup Lee³, Bin Lai⁴, Christian Solem⁵

Affiliations

¹ National Food Institute, Technical University of Denmark, Kongens Lyngby, 2800, Denmark.
² Department of Chemistry and Bioscience, Aalborg University, 9220 Aalborg, Denmark.
³ Department of Chemical and Biomolecular Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Republic of Korea.
⁴ BMBF junior research group Biophotovoltaics, Helmholtz Center for Environmental Research - UFZ, Leipzig 04318, Germany. Electronic address: bin.lai@ufz.de.
⁵ National Food Institute, Technical University of Denmark, Kongens Lyngby, 2800, Denmark. Electronic address: chso@food.dtu.dk.

PMID: 37776913
DOI: 10.1016/j.biortech.2023.129813

Abstract

Anodic electro-fermentation (AEF), where an anode replaces the terminal electron acceptor, shows great promise. Recently a Lactococcus lactis strain blocked in NAD⁺ regeneration was demonstrated to use ferricyanide as an alternative electron acceptor to support fast growth, but the need for high concentrations of this non-regenerated electron acceptor limits practical applications. To address this, growth of this L. lactis strain, and an adaptively evolved (ALE) mutant with enhanced ferricyanide respiration capacity were investigated using an anode as electron acceptor in a bioelectrochemical system (BES) setup. Both strains grew well, however, the ALE mutant significantly faster. The ALE mutant almost exclusively generated 2,3-butanediol, whereas its parent strain mainly produced acetoin. The ALE mutant interacted efficiently with the anode, achieving a record high current density of 0.81 ± 0.05 mA/cm². It is surprising that a Lactic Acid Bacterium, with fermentative metabolism, interacts so well with an anode, which demonstrates the potential of AEF.

Keywords: 2,3-butanediol; Acetoin; Anodic electro-fermentation; Bioelectrochemical system; Lactococcus lactis.