Metagenomic insight into methanogenic reactors promoting direct interspecies electron transfer via granular activated carbon

Park, Jeong Hoon; Park, Jong‐Hun; Seong, Hoon Je; Sul, Woo Jun; Jin, Kang Hyun; Park, Hee Deung

doi:10.1016/j.biortech.2018.03.050

Cited by 128 publications

(37 citation statements)

References 44 publications

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“…The EET from EAB to the anode has been demonstrated to be facilitated via c-type cytochromes and conductive nanowire or pili (Hernández-Eligio et al, 2020), while fundamental aspects of EET mechanisms in methanogenic biocathode (i.e., direct electron transport from the electrode to methanogens) is still not well understood. Previous reports postulated that conductive pili and c-type cytochromes could play an important role in EET to electrotrophic methanogens from DIET-partners (i.e., electroactive bacteria) (Park et al, 2018b; Rotaru et al, 2014). Based on the authors’ knowledge, this study also first reports the expression of EET genes for methanogenic biocathode.…”

Section: Resultsmentioning

confidence: 99%

“…The EET from EAB to the anode has been demonstrated to be facilitated via c-type cytochromes and conductive nanowire or pili 74 , while the significance of EET in methanogenic biocathode is still ambiguous. However, previous reports postulated that conductive pili and c-type cytochromes could play an important role in DIET from EAB to methanogens 75,76 .…”

Section: Expression Of Eet Genesmentioning

confidence: 90%

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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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Section: Resultsmentioning

confidence: 99%

Section: Expression Of Eet Genesmentioning

confidence: 90%

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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“…Universal bacterial primers 341F (5′‐CCTACGGGNGGCWGCAG‐3′) and 805R (5′‐GACTACHVGGGTATCTAATCC‐3′), and universal archaeal primers 787F (5′‐ATTAGATACCCSBGTAGTCC‐3′) and 1059R (5‐GCCATGCACCWCCTCT‐3′) were used to establish the microbial abundance in gene copy numbers of both archaeal and bacterial genes 23 in our AnDMBR and CSTR‐only systems. Amplification was performed using identical qPCR mixtures and cycler conditions as those previously reported by Cayetano et al 17 …”

Section: Methodsmentioning

confidence: 99%

Waste activated sludge treatment in an anaerobic dynamic membrane bioreactor at varying hydraulic retention time: Performance monitoring and microbial community analysis

et al. 2020

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In this study, the variations in system performance and microbial community composition when treating waste activated sludge without prior chemical or physical pretreatment in anaerobic systems is examined. Two lab-scale digesters, namely anaerobic dynamic membrane bioreactor (AnDMBR) and continuously stirred tank reactor (CSTR), were operated and maintained under mesophilic conditions at varying hydraulic retention times (10-25 days). Decreasing the hydraulic retention time (HRT) affected the methane yield (MY) and methane production rate (MPR) proportionally in both systems. The AnDMBR's maximum MY of 252 mL CH 4 /g-VS and MPR of 0.73 L/L/d were 25% and 34% higher than those obtained using the CSTR, respectively. Moreover, a decrease in HRT was accompanied by accumulation of butyric acid in the CSTR, which caused further performance deterioration. In both systems, AnDMBR's dynamic membrane acted as an added layer preventing methanogen wash-out and retaining the essential microorganisms for stable sludge treatment. Dominance in the microbial composition shifted from a strict acetoclastic to a mixed acetoclastic and hydrogenotrophic methanogenic community and that a decrease in the ration of Bacteroidetes to Firmicutes was associated with the increased MY.

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“…Shrestha et al [5] observed upregulation of the OmcT gene in a DIET-performing co-culture relative to a MIET-performing co-culture. Other genes/transcripts/proteins in Table 1 have been linked to DIET by monitoring their up/down regulation or expression upon DIET promotion [13,35,36]. However, some of the genes/transcripts/proteins listed in Table 1 can be involved with other cell functions [37], precluding them as unique identifiers for DIET.…”

Section: Detection Of Species Genes Transcripts or Proteinsmentioning

confidence: 99%

“…For example, it has been hypothesized that genes associated with pili formation (e.g., PilA and OmcS) are downregulated when conductive materials are provided by allowing DIET over long(er) distances without the need for pili [13,36]. Furthermore, our knowledge regarding DIET mechanisms is still rapidly expanding [38][39][40].…”

Section: Detection Of Species Genes Transcripts or Proteinsmentioning

confidence: 99%

Improving anaerobic digestion via direct interspecies electron transfer requires development of suitable characterization methods

Steendam¹,

Smets²,

Skerlos³

et al. 2019

Current Opinion in Biotechnology

117

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Metagenomic insight into methanogenic reactors promoting direct interspecies electron transfer via granular activated carbon

Cited by 128 publications

References 44 publications

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

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

Waste activated sludge treatment in an anaerobic dynamic membrane bioreactor at varying hydraulic retention time: Performance monitoring and microbial community analysis

Improving anaerobic digestion via direct interspecies electron transfer requires development of suitable characterization methods

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