<i>Acidithiobacillus ferrooxidans</i> as a Bioelectrocatalyst for Conversion of Atmospheric CO₂ into Extracellular Pyruvic Acid

Abstract

This study investigated the ability of the bacterium Acidithiobacillus ferrooxidans to convert CO 2 into organic compounds in batch culture and during electrochemical cultivation. Metabolites secreted into the culture medium were detected and analyzed by HPLC and mass spectroscopy, which revealed that pyruvic acid was one of the organic acids present in both cultures. We found that although pyruvic acid acted as a strong inhibitor for microbial growth in batch cultures, microbial CO 2 fixation activity in electrochemical cultures was not significantly affected by the addition of excess pyruvic acid. Together, these findings indicate that A. ferrooxidans is a promising bioelectrocatalyst for the conversion of CO 2 into extracellular organic compounds.

From chemolithoautotrophs to electrolithoautotrophs: CO2 fixation by Fe(II)-oxidizing bacteria coupled with direct uptake of electrons from solid electron sources

“…In the presence of Fe 2+ ions, the onset potential for cathodic current generation was estimated to be +0.65 V, as indicated in the peak in the logarithmic plot for current. This value is close to the redox potential of Fe 3+ /Fe 2+ couple and consistent well with the previously reported model for electrochemical cultivation of A. ferrooxidans ( Yunker and Radovich, 1986 ; Matsumoto et al, 1999 , 2002 ; Ishii et al, 2012 ). Namely, diffusible Fe 2+ and Fe 3+ ions serve as an electron shuttle which bridges electron transfer between planktonic cells and electrodes.…”

“…To evaluate the redox potential of electrical conduits established at the cell-electrode interface, electrodes covered with viable cells were examined by linear sweep (LS) voltammetry (solid line, Figure 2 ). As a reference, we also conducted LS voltammetry for cell cultures containing soluble Fe 2+ ions, a system known as electrochemical cultivation of A. ferrooxidans (broken line, Figure 2 ) ( Yunker and Radovich, 1986 ; Matsumoto et al, 1999 , 2002 ; Ishii et al, 2012 ). In the presence of Fe 2+ ions, the onset potential for cathodic current generation was estimated to be +0.65 V, as indicated in the peak in the logarithmic plot for current.…”

Microbial Chromate Reduction Coupled to Anaerobic Oxidation of Elemental Sulfur or Zerovalent Iron

“…It has been reported that Thiobacillus could oxidize S(0) to release electrons and gain energy to synthesize metabolites to reduce Cr(VI). 56,57 The accumulated Blvii28 (17.9%) might play an important role in autotrophic S(0) oxidation in B−S, which has been reported to be able to generate hydrogen for S(0) autotrophic microbes. 58 In both B−S and B−Fe, archaeal communities were also observed to shift significantly.…”

Enhancing isobutyric acid production from engineered Acidithiobacillus ferrooxidans cells via media optimization

“…Its metabolic capability has led to its utilization in bioprocesses including copper bioleaching and desulfurization of coal and sour gases (Monticello and Finnerty, 1985). We have been investigating these cells for use as a unique biotechnology platform enabling biofuels and biomass to be produced from carbon dioxide and electricity (termed electrofuels) (Conrado et al, 2013;Ishii et al, 2012;Li and Liao, 2013;Nybo et al, 2015). We have reported the genetic modification of A. ferrooxidans to produce exogenous chemicals (isobutyric acid [IBA] or heptadecane) from carbon dioxide (Kernan et al, 2015).…”