Microbial electrosynthesis of organic chemicals from CO2 by Clostridium scatologenes ATCC 25775T

Abstract

Background: The conversion of CO 2 into high value-added products has a very important environmental and economic significance. Microbial electrosynthesis (MES) is a promising technology, which adopts a bioelectrochemical system to transform CO 2 into organic chemicals. Results: In this study, Clostridium scatologenes ATCC 25775 T , an anaerobic acetogenic bacterium, demonstrated its utility as a biocatalyst in a MES system, for the first time. With the cathodic potential of the MES system decreased from − 0.6 to − 1.2 V (vs. Ag/AgCl), the current density of the MES, and the production of organic chemicals, increased. Combining the genetic analysis and the results of the wet lab experiments, we believe C. scatologenes may accept electrons directly from the cathode to reduce CO 2 into organic compounds at a potential of − 0.6 V. The acetic and butyric acid reached a maximum value of 0.03 and 0.01 g/L, respectively, and the maximum value of total coulombic efficiency was about 84%, at the potential of − 0.6 V. With the decrease in cathodic potentials, both direct electron transfer and exogenous electron shuttle, H 2 might be adopted for the C. scatologenes MES system. At a potential of − 1.2 V, acetic acid, butyric acid and ethanol were detected in the cathodic chamber, with their maximum values increasing to 0.44, 0.085 and 0.015 g/L, respectively. However, due to the low H 2 utilization rate by the C. scatologenes planktonic cell, the total coulombic efficiency of the MES system dropped to 37.8%. Conclusion: Clostridium scatologenes is an acetogenic bacterium which may fix CO 2 through the Wood-Ljungdahl pathway. Under H 2 fermentation, C. scatologenes may reduce CO 2 to acetic acid, butyric acid and ethanol. It can also be used as the biocatalyst in MES systems.

A variety of hydrogenotrophic enrichment cultures catalyse cathodic reactions

“…The working electrode potential was controlled using Wenking M lab potentiostat and the current was recorded by MlabSci470c sequencer multichannel potentiostat software (version 4.7.0). Since the electrode potential has a strong effect on the magnitude of the cathodic current 31,64 , the MEC were operated at both −0.65 V and −0.8 V versus SHE. The bioelectrochemical activity of the cathode was investigated using cyclic voltammetry (CV).…”

Carbon dioxide to bio-oil in a bioelectrochemical system-assisted microalgae biorefinery process

“…42,43 Clostridium autoethanogenum also has a role in autotrophic ethanol production from industrial waste gases. 44,45 Sequences retrieved from HT2 showed a higher similarity to Clostridium aciditolerans and Clostridium nitrophenolicum (96% identity), so far still not reported as typical species in MES processes. Although additional tests should be performed to conrm the identity of the most abundant ASVs in HT2, the absence of true homoacetogenic clostridia is intriguing in view of the acetate production.…”

Microbial electrosynthesis of methane and acetate—comparison of pure and mixed cultures

“…Investigated S. acidovorans and S. malonica showed APRs of 2.65 ± 0.85 and 2.73 ± 0.29 g day −1 m −2 , which are comparable with the result of S. ovata in the same MES setup (Aryal et al 2017 ). Further studies investigated different Clostridium strains, focusing on the production of organic chemicals from CO 2 by MES (Liu et al 2018b ; Wang et al 2020 ). One of the main products was acetate with a production rate of up to 34.6 ± 1.1 g day −1 m −2 (Roy et al 2021 ).…”

“…One of the main products was acetate with a production rate of up to 34.6 ± 1.1 g day −1 m −2 (Roy et al 2021 ). Overall, the literature suggests that the electron transfer in pure culture MES occurs via H 2 (IDET) and direct electron transfer (DET), depending on the number of suspended cells or biofilm formation (Aryal et al 2017 ; Liu et al 2018b ; Krige et al 2021 ).…”