Microbial Ecology of Anodic Biofilms: From Species Selection to Microbial Interactions

Flayac, Jean-Clément; Trably, Eric; Bernet, Nicolas

doi:10.1007/978-3-319-66793-5_4

Cited by 4 publications

(3 citation statements)

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“…These conflicting observations suggest that there are other factors beyond thermodynamics, such as energy investment [ 35 ], that influence the utilization preference between different electron sources. The preferred utilization of propionate over butyrate observed in this study may also be attributed to the potential existence of specialized exoelectrogenic bacteria, such as Geobacter anodireducens , capable of directly utilizing propionate for current generation [ 56 , 64 ]. Lactate, which has a similar molecular structure to propionate, can also be directly converted to electrical current by some Geobacter species [ 53 ].…”

Section: Resultsmentioning

confidence: 99%

“…Lactate can be consumed directly by exoelectrogenic bacteria (e.g. Geobacter sulfurreducens PCA) without electron shuttle through intracellular conversion of lactate to acetate and hydrogen, followed by their oxidation to electrons, and this overall oxidation reaction is known to be highly spontaneous process [ 65 ]. Although the anodic microbial community was not analyzed in this study, it is possible that exoelectrogenic bacteria, which can directly utilize propionate (and lactate), were active and helped to facilitate the utilization of propionate (and lactate) in the experimental MECs.…”

Section: Resultsmentioning

confidence: 99%

“…Another point to consider regarding the exoelectrogenic propionate utilization is the effect of pH. Syntrophic degradation of propionate can occur through two pathways: the acetate/H 2 pathway, which is more favorable at a pH below 6.37, or the acetate/formate pathway, which is more favorable at a pH above that [ 64 ]. Given that the latter pathway is more energetically favorable than the former ( Table 1 ), the less acidic anodic pH of AEM-MECs (6.2–6.7) compared to PEM-MECs (5.5–6.0) likely contributed to the more efficient degradation of propionate in the AEM-MECs ( Figure 5 ).…”

Section: Resultsmentioning

confidence: 99%

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A study of electron source preference and its impact on hydrogen production in microbial electrolysis cells fed with synthetic fermentation effluent

Choi,

Kim,

Choi

et al. 2023

Bioengineered

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Fermentation effluents from organic wastes contain simple organic acids and ethanol, which are good electron sources for exoelectrogenic bacteria, and hence are considered a promising substrate for hydrogen production in microbial electrolysis cells (MECs). These fermentation products have different mechanisms and thermodynamics for their anaerobic oxidation, and therefore the composition of fermentation effluent significantly influences MEC performance. This study examined the microbial electrolysis of a synthetic fermentation effluent (containing acetate, propionate, butyrate, lactate, and ethanol) in two-chamber MECs fitted with either a proton exchange membrane (PEM) or an anion exchange membrane (AEM), with a focus on the utilization preference between the electron sources present in the effluent. Throughout the eight cycles of repeated batch operation with an applied voltage of 0.8 V, the AEM-MECs consistently outperformed the PEM-MECs in terms of organic removal, current generation, and hydrogen production. The highest hydrogen yield achieved for AEM-MECs was 1.26 L/g chemical oxygen demand (COD) fed (approximately 90% of the theoretical maximum), which was nearly double the yield for PEM-MECs (0.68 L/g COD fed). The superior performance of AEM-MECs was attributed to the greater pH imbalance and more acidic anodic pH in PEM-MECs (5.5–6.0), disrupting anodic respiration. Although butyrate is more thermodynamically favorable than propionate for anaerobic oxidation, butyrate was the least favored electron source, followed by propionate, in both AEM- and PEM-MECs, while ethanol and lactate were completely consumed. Further research is needed to better comprehend the preferences for different electron sources in fermentation effluents and enhance their microbial electrolysis.

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