Syngas Fermentation to Acetate and Ethanol with Adaptative Electroactive Carboxydotrophs in Single Chambered Microbial Electrochemical System

Abstract

Microbial electrosynthesis system (MES; single-chambered) was fabricated and evaluated with carbon cloth/graphite as a working/counter electrode employing an enriched microbiome. Continuous syngas sparging (at working electrode; WE) enabled the growth of endo electrogenic bacteria by availing the inorganic carbon source. Applied potential (−0.5 V) on the working electrode facilitated the reduction in syngas, leading to the synthesis of fatty acids and alcohols. The higher acetic acid titer of 3.8 g/L and ethanol concentration of 0.2 g/L was observed at an active microbial metabolic state, evidencing the shift in metabolism from acetogenic to solventogenesis. Voltammograms evidenced distinct redox species with low charge transfer resistance (Rct; Nyquist impedance). Reductive catalytic current (−0.02 mA) enabled the charge transfer efficiency of the cathodes favoring syngas conversion to products. The surface morphology of carbon cloth and system-designed conditions favored the growth of electrochemically active consortia. Metagenomic analysis revealed the enrichment of phylum/class with Actinobacteria, Firmicutes/Clostridia and Bacilli, which accounts for the syngas fermentation through suitable gene loci.

Syngas fermentation to ethanol: CODH/AdhE1 gene expression and microbial community dynamics

“…The amount of IC fixation rate (ICFR; mg L −1 h −1 ) in the enriched culture with CO 2 /CO was computed using the following eqn (1). 13 where M 1 is the acetic acid (g L −1 ) at t 1 (h) and M 0 is the acetic acid (g L −1 ) at t 0 (h).…”

“…The amount of IC xation rate (ICFR; mg L −1 h −1 ) in the enriched culture with CO 2 /CO was computed using the following eqn (1). 13…”

Hybrid electrosynthesis as non‐genetic approach for regulating microbial metabolism towards waste valorization in circular framework

“…Acidogenesis is key biological step in waste valorization (solid/liquid/gaseous) towards microbial conversion to predominantly carboxylate platform products (volatile fatty acids [VFA], that is, acetic, propionic, butyric, iso‐butyric, valeric and iso‐valeric acids), along with alcohols, aldehydes, H 2 and CO 2 production (Tharak & Venkata Mohan, 2022 ). The spectrum of products is of huge interest due to their commercial applications and economic viability garnered from the process (Venkata Mohan & Katakojwala, 2021 ).…”

“…Biogenic waste (solid/liquid/gaseous) has huge potential to capture market, when cohesively involved with individual advantages of the bioprocesses in an integrated manner (Venkata Mohan et al, 2016 ; Venkata Mohan & Katakojwala, 2021 ). Non‐genetic biological approaches could be economically viable with higher reach for execution at variable operational scales for multiple products benefit (renewable chemicals, energy and fuels) with carbon neutralization (Tharak & Venkata Mohan, 2022 ). Hence, the advantage of biocatalysts with regulation on the process limitations and mechanism towards maximizing products conversion using waste feedstock could be considered a challenge to address in the context of waste biorefinery.…”

“…Biological processes are considered sustainable options in waste utilization/conversion towards renewable chemicals, energy and fuels production (Tharak & Venkata Mohan, 2022 ; Van et al, 2020 ). Anaerobic fermentation (AF)/anaerobic digestion (AD) are potential bioconversion processes for treating diverse biogenic waste/wastewaters resulting in energy/product spectrum generation (Van et al, 2020 ; Zhao et al, 2020 ).…”