Anode potentials regulate Geobacter biofilms: New insights from the composition and spatial structure of extracellular polymeric substances

Yang, Guiqin; Huang, Lingyan; Yu, Zhen; Liu, Xiaoming; Chen, Shanshan; Zeng, Jianxiong; Zhou, Shungui; Li, Zhuang

doi:10.1016/j.watres.2019.05.027

Cited by 146 publications

(65 citation statements)

References 54 publications

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“…Each reactor was equipped with a CNT membrane module (1.02 × 10 −3 m 2 working area), six graphite rods (Φ 1.0× 6.0 cm), and a silver chloride electrode as the anode, cathode, and reference electrode, respectively. According to the previous studies 47–50 , two reactors in which the membranes were imposed with −0.3 and −0.2 V anode potential were referred to as R-0.3 and R-0.2, respectively. The third reactor was not imposed with any potential to be used as the control (referred to as R–M).…”

Section: Methodsmentioning

confidence: 99%

Fouling-resistant biofilter of an anaerobic electrochemical membrane reactor

Zhang

2019

Nat Commun

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Membrane fouling is a considerable challenge for the stable operation of anaerobic membrane-based bioreactors. Membrane used as a cathode is a common measure to retard fouling growth in anaerobic electrochemical membrane bioreactors (AnEMBR), which; however, cannot avoid the fouling growth. Here we report a strategy using the membrane as an anode to resist membrane fouling in an AnEMBR. Although aggravating in the initial stage, the fouling on the anode membrane is gradually alleviated by the anode oxidation with enriching exoelectrogens to finally achieve a dynamic equilibrium between fouling growth and decomposition to maintain the operation stable. A mesh-like biofilter layer composed of cells with less extracellular polymeric substance (EPS) is formed on the membrane surface to lower the trans-membrane pressure and promote the interception of the anode membrane. The membrane has high electron storage and transfer capacities to accelerate the oxidation of the intercepted fouling materials, especially, the redundant EPSs of the biofilter layer.

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Section: Methodsmentioning

confidence: 99%

Fouling-resistant biofilter of an anaerobic electrochemical membrane reactor

Zhang

2019

Nat Commun

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“…A recent study reported that the current generated from anode biofilms was positively associated with EPS protein content and negatively correlated to carbohydrates in EPS (Yang et al, 2019). In this study, both carbohydrates and proteins were considerably higher in EPS extracted from stainless steel biocathode than that of carbon fiber biocathode.…”

Section: Resultsmentioning

confidence: 99%

Section: Eps Structures and Characteristicsmentioning

confidence: 99%

“…The details of EPS extraction and analytical methods for various EPS components (proteins, carbohydrates, eDNA, heme-binding proteins, and uronic acid) are provided in the Supporting Information. These five major EPS components were selected based on the EPS components previously found in electroactive anode biofilms 20,[46][47][48] . Furthermore, these EPS components were also found in archaeal biofilms in conventional anaerobic biofilm reactors 49,50 .…”

Section: Eps and Ros Analysesmentioning

confidence: 99%

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Characterization and significance of extracellular polymeric substances, reactive oxygen species, and extracellular electron transfer in methanogenic biocathode

Zakaria

Dhar

2020

Preprint

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Carbon-based electrodes have been mostly used as a biocathode material in microbial electrolysis cell assisted anaerobic digestion (MEC-AD) due to their excellent biocompatibility and higher surface area over metal-based electrodes. Here, we report a multifaceted approach combining characterization of microbial communities, extracellular polymeric substances (EPS), redox oxygen species (ROS), and expression of genes associated with extracellular electron transfer (EET) to shed light on mechanisms governing electro-methanogenic activity in different biocathode materials. Carbon fiber and stainless-steel mesh biocathode were tested in MEC-AD systems fed with synthetic glucose medium. Despite the higher specific surface area provided by carbon fiber biocathode, methanogenesis performance was much inferior (100.3 mL CH4) than that obtained from a stainless steel biocathode (179.5 mL CH4). Interestingly, biofilms did not entirely cover the surfaces of carbon fibers, while stainless steel biocathode showed evenly denser biofilms with higher biovolume (30.2±4.2 vs. 13.5±2.8 μm3/μm2). Analyses of microbial communities indicated that the key mechanism for electro-methanogenesis in both reactors was hydrogenotrophic methanogenesis by Methanobacterium species. The redox activity of EPS derived from biocathode, as well as expressions of EET genes, suggested that electro-methanogenesis via direct electron transfer might have occurred to some extent in both biocathodes. Higher abundance of strictly hydrogenotrophic Methanobacterium sp. and homoacetogenic Acetobacterium appeared to play a major role in higher methanogenesis performance from stainless steel biocathode. It was possibly attributed to effective catalysis of hydrogen evolution reaction (HER) on stainless steel biocathode. The most considerable secretion of EPS accompanied by the lowest ROS level in stainless steel biocathode indicated that higher EPS possibly protected cells from harsh metabolic conditions (e.g., unfavorable local pH) induced by faster HER. The results of this study have important significance in the development of effective biocathode for MEC-AD systems.HighlightsStainless-steel mesh outperformed carbon fibers for methanogenic biocathode.Multifaceted characterization of biofilms unveiled underlying mechanisms.The results confirmed H2-utilizing methanogenesis is the dominant pathway.Homoacetogenesis only played a crucial role in the stainless-steel biocathode.Biocathode EPS might be responsible for superior methanogenesis.Graphical Abstract

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“…In a polarized system, the working electrode was polarized at 0.0V versus SCE using a CHI1000C electrochemical workstation (CH Instruments Inc., Shanghai, China) to culture the anode biofilm. Such potential is optimal for electroactive biofilm growth on graphite plate anodes (Yang et al, 2019a; Zhu et al, 2014). The current densities were recorded every 100s.…”

Section: Methodsmentioning

confidence: 99%

Stratified microbial structure and activity within anode biofilm during electrochemically assisted brewery wastewater treatment

Mai

Yang

Cao

et al. 2020

Biotech & Bioengineering

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In a bioelectrochemical system (BES), microbial community of anode biofilm is crucial to BES performance. In this study, the stratified pattern of community structure and activity of an anode‐respiring biofilm in a BES fueled with brewery wastewater was investigated over time. The anode biofilm exhibited a superior performance in the removal of ethanol to that of an open‐circuit system. The electrical current density reached a high level of 0.55mA/cm2 with a Coulombic efficiency of 71.4%, but decreased to 0.18mA/cm2 in the late stage of operation. A mature biofilm developed a more active outer layer covering a less active inner core, although the activities of the outer and inner layers of biofilm were similar in the early stage. More Geobacter spp., typical exoelectrogens, were enriched in the outer layer than in the inner layer of biofilm in the early stage, while more Geobacter spp. were distributed in the inner layer than in the outer layer in the late stage. The inactive and Geobacter‐occupied inner layer of biofilm might be responsible for the decreased electricity generation from wastewater in the late stage of operation. This study provides better understanding of the effect of anode biofilm structure on BES performance.

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Anode potentials regulate Geobacter biofilms: New insights from the composition and spatial structure of extracellular polymeric substances

Cited by 146 publications

References 54 publications

Fouling-resistant biofilter of an anaerobic electrochemical membrane reactor

Fouling-resistant biofilter of an anaerobic electrochemical membrane reactor

Characterization and significance of extracellular polymeric substances, reactive oxygen species, and extracellular electron transfer in methanogenic biocathode

Stratified microbial structure and activity within anode biofilm during electrochemically assisted brewery wastewater treatment

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