• Journal of Microbiology and Biotechnology
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• 제19권12호
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• pp.1665-1671
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• 2009

Anaerobic digestion sludge was cultivated in an electrochemical bioreactor (ECB) to enrich the hydrogenotrophic methanogens. A modified graphite felt cathode with neutral red (NR-cathode) was charged with electrochemical reducing power generated from a solar cell. The methane and carbon dioxide collected in a Teflon bag from the ECB were more than 80 ml/l of reactant/day and less than 20 ml/l of reactant/day, respectively, whereas the methane and carbon dioxide collected from a conventional bioreactor (CB) was around 40 ml/l of reactant/day, respectively. Moreover, the maximal volume ratios of methane to carbon dioxide (M/C ratio) collected in the Teflon bag from the ECB and CB were 7 and 1, respectively. The most predominant methanogens isolated from the CB on the $20^{th}$, $80^{th}$, and $150^{th}$ days of incubation were hydrogenotrophs. The methanogenic diversity analyzed by temperature gradient gel electrophoresis (TGGE) of the 16S rDNA variable region was higher in the ECB than in the CB. The DNA extracted from the TGGE bands was more than 95% homologous with hydrogenotrophic methanogens in the ECB, but was an aceticlastic methanogen in the CB. In conclusion, the ECB was demonstrated as a useful system for enriching hydrogenotrophic methanogens and increasing the M/C ratio of the gas product.

• 한국수소및신에너지학회논문집
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• 제30권3호
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• pp.269-275
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• 2019

This study was conducted to evaluate the microbial communities in coupled system of a microbial electrolysis cell and an anaerobic digestion. Glucose, butyric acid, propionic acid and acetic acid were used as substrates. The maximum methane production and methane production rate of propionic acid respectively were $327.9{\pm}6.7mL\;CH_4/g\;COD$ and $28.3{\pm}3.1mL\;CH_4/g\;COD{\cdot}d$, which were higher than others. Microbial communities' analyses indicated that acetoclastic methangens were predominant in all systems. But the proportion of hydrogenotrophic methanogens was higher in the system using propionic acid as a substrate when compared to others. In coupled system of a microbial electrolysis cell and anaerobic digestion, the methane production was higher as the distribution of hydrogen, which was generated by substrate degradation, and proportion of hydrogenotrophic methanogens was higher.

• Journal of Microbiology and Biotechnology
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• 제23권2호
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• pp.137-143
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• 2013

The diversity and distribution of methanogenic archaea in a four-compartment anaerobic baffled reactor (ABR) treating sugar refinery wastewater were investigated by polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE). At an organic loading rate of 5.33 kg $COD/m^3{\cdot}day$, the ABR could perform steadily with the mean chemical oxygen demand (COD) removal of 94.8% and the specific $CH_4$ yield of 0.21 l/g $COD_{removed}$. The $CH_4$ content in the biogas was increased along the compartments, whereas the percentage of $H_2$ was decreased, indicating the distribution characteristics of the methanogens occurred longitudinally down the ABR. A high phylogenetic and ecological diversity of methanogens was found in the ABR, and all the detected methanogens were classified into six groups, including Methanomicrobiales, Methanosarcinales, Methanobacteriales, Crenarchaeota, Arc I, and Unidentified. Among the methanogenic population, the acid-tolerant hydrogenotrophic methanogens including Methanoregula and Methanosphaerula dominated the first two compartments. In the last two compartments, the dominant methanogenic population was Methanosaeta, which was the major acetate oxidizer under methanogenic conditions and could promote the formation of granular sludge. The distribution of the hydrogenotrophic (acid-tolerant) and acetotrophic methanogens in sequence along the compartments allowed the ABR to perform more efficiently and steadily.

• Journal of Microbiology and Biotechnology
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• 제26권8호
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• pp.1409-1419
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• 2016

The effect of pH on propionate degradation in an upflow anaerobic sludge blanket (UASB) reactor containing propionate as a sole carbon source was studied. Under influent propionate of 2,000 mg/l and 35℃, propionate removal at pH 7.5-6.8 was above 93.6%. Propionate conversion was significantly inhibited with stepwise pH decrease from pH 6.8 to 6.5, 6.0, 5.5, 5.0, 4.5, and then to 4.0. After long-term operation, the propionate removal at pH 6.5-4.5 maintained an efficiency of 88.5%-70.1%, whereas propionate was hardly decomposed at pH 4.0. Microbial composition analysis showed that propionate-oxidizing bacteria from the genera Pelotomaculum and Smithella likely existed in this system. They were significantly reduced at pH ≤5.5. The methanogens in this UASB reactor belonged to four genera: Methanobacterium, Methanospirillum, Methanofollis, and Methanosaeta. Most detectable hydrogenotrophic methanogens were able to grow at low pH conditions (pH 6.0-4.0), but the acetotrophic methanogens were reduced as pH decreased. These results indicated that propionate-oxidizing bacteria and acetotrophic methanogens were more sensitive to low pH (5.5-4.0) than hydrogenotrophic methanogens.

• Journal of Microbiology and Biotechnology
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• 제24권11호
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• pp.1464-1472
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• 2014

The microbial community structures of two continuous stirred tank reactors digesting turkey manure with pine wood shavings as well as chicken and swine manure were investigated. The reactor fed with chicken/swine wastes displayed the highest organic acids concentration (up to 15.2 g/l) and ammonia concentration (up to 3.7 g/l ammonium nitrogen) and generated a higher biogas yield (up to $366ml/g_{VS}$) compared with the reactor supplied with turkey wastes (1.5-1.8 g/l of organic acids and 1.6-1.7 g/l of ammonium levels; biogas yield was up to $195ml/g_{VS}$). The microbial community diversity was assessed using both sequencing and profiling terminal restriction fragment length polymorphisms of 16S rRNA genes. Additionally, methanogens were analyzed using methyl coenzyme M reductase alpha subunit (mcrA) genes. The bacterial community was dominated by members of unclassified Clostridiales with the prevalence of specific clostridial phylotypes in each reactor, indicating the effect of the substrate type on the community structure. Of the methanogenic archaea, methanogens of the genus Methanosarcina were found in high proportions in both reactors with specific methanosarcinas in each reactor, whereas the strict hydrogenotrophic methanogens of Methanoculleus sp. were found at significant levels only in the reactor fed with chicken/swine manure (based on the analyses of 16S rRNA gene). This suggests that among methanogenic archaea, Methanosarcina species which have different metabolic capabilities, including aceticlastic and hydrogenotrophic methanogenesis, were mainly involved in anaerobic digestion of turkey wastes.

• Journal of Microbiology and Biotechnology
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• 제27권8호
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• pp.1513-1518
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• 2017

Anaerobic mono- and co-digestion of sewage sludge and food waste leachate (FWL) were performed by assessing methane production and characterizing microbial communities. Anaerobic digestion (AD) of waste activated sludge (WAS) alone produced the lowest methane ($281ml\;CH_4$), but an approximately 80% increase in methane production was achieved via co-digestion of WAS and FWL ($506ml\;CH_4$). There were less differences in the diversity of bacterial communities in anaerobic digesters, while archaeal (ARC) and bacterial (BAC) amounts reflected AD performance. Compared with the total ARC and BAC amounts in the mono-digestion of WAS, the ARC and BAC amounts increased two and three times, respectively, during co-digestion of FWL and WAS. In characterized archaeal communities, the dominant ratio of hydrogenotrophic methanogens in the mono-digestion of WAS approached nearly a 1:1 ratio of the two acetoclastic and hydrogenotrophic methanogens in the co-digestion of FWL and WAS. The ARC/BAC ratio in the digesters varied in the range of 5.9% to 9.1%, indicating a positive correlation with the methane production of AD.

• 한국환경과학회지
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• 제30권12호
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• pp.1093-1100
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• 2021

The present study investigated the effect of ammonia load on microbial communities in mesophilic anaerobic digestion of propionic acid. A laboratory-scale continuous anaerobic digester treating propionic acid as a sole organic substrate was operated under non-inhibitory condition and inhibitory conditions with ammonia (1.5 g and 3.5 g ammonia-N/L, respectively), and bacterial and archaeal communities in the steady states of each ammonia condition were analyzed using high-throughput sequencing. Thirteen bacterial families were detected as abundant bacterial groups in mesophilic anaerobic digestion of propionic acid. Increase in ammonia concentration resulted in significant shifts in microbial community structures. Syntorophobacter, Pelotomaculum, and Thermovigra were determined as the dominant groups of (potential) propionate oxidizing bacteria in the non-inhibitory condition, whereas Cryptanaerobacter and Aminobacterium were the dominant groups of (potential) propionate oxidizing bacteria in the ammonia-inhibitory condition. Methanoculleus and Methanosaeta were the dominant methanogens. Acetate-oxidation coupled with hydrogenotrophic methanogenesis might be enhanced with increases in the relative abundances of Methanoculleus and Tepidanaerobacter acetatoxydans under the ammonia-inhibitory condition. The results of the present study could be a valuable reference for microbial management of anaerobic digestion systems that are exposed to ammonia inhibition and propionic acid accumulation.

• 한국환경과학회지
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• 제31권12호
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• pp.1051-1059
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• 2022

This study investigated microbial communities and their diversity in a full-scale mesophilic anaerobic digester treating sewage sludge. Influent sewage sludge and anaerobic digester samples collected from a wastewater treatment plant in Busan were analyzed using high-throughput sequencing. It was found that the microbial community structure and diversity in the anaerobic digester could be affected by inoculation effect with influent sewage sludge. Nevertheless, distinct microbial communities were identified as the dominant microbial communities in the anaerobic digester. Twelve genera were identified as abundant bacterial communities, which included several groups of syntrophic bacteria communities, such as Candidatus Cloacimonas, Cloacimonadaceae W5, Smithella, which are (potential) syntrophic-propionate-oxidizing bacteria and Mesotoga and Thermovigra, which are (potential) syntrophic-acetate-oxidizing bacteria. Lentimicrobium, the most abundant genus in the anaerobic digester, may contribute to the decomposition of carbohydrates and the production of volatile fatty acids during the anaerobic digestion of sewage sludge. Of the methanogens identified, Methanollinea, Candidatus Methanofastidiosum, Methanospirillum, and Methanoculleus were the dominant hydrogenotrophic methanogens, and Methanosaeta was the dominant aceticlastic methanogens. The findings may be used as a reference for developing microbial indicators to evaluate the process stability and process efficiency of the anaerobic digestion of sewage sludge.

• 유기물자원화
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• 제7권2호
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• pp.25-34
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• 1999

프로피온산의 혐기성 분해시 구리의 잠재적인 저해효과를 평가하기 위하여 회분식 실험을 수행하였다 프로피온산의 혐기성 분해시 구리의 저해효과는 중간 생성물, 최종 메탄 수율 및 비메탄 활성도를 이용하여 평가하였다. 구리의 농도 $2.5mg\;Cu^{2+}/1$에서는 저해 현상이 거의 발생하지 않았으나. 농도 증가에 따라 저해효과가 점차 증가하는 경향을 보였다. 최종 메탄 발생량 및 비메탄 활성도를 이용하여 산정한 50% 저해농도는 각각 33.8 및 $24.1mg\;Cu^{2+}/gVSS$로 나타났다. 최종 메탄 수율을 이용하여 산정한 저해효과는 운전기간이 지속됨에 따라 미생물 적응 및 첨가한 구리의 용존성 리간드와 체외효소와 결합으로 인하여 점차 저감되는 현상이 나타났다. 초기 메탄 발생속도를 근거로 산정한 비메탄 활성도는 이와 같은 영향을 상대적으로 제외할 수 있으므로 중금속에 의한 저해효과를 보다 정확하게 산정할 수 있을 것으로 판단된다. 황산염을 첨가한 경우 황산염 환원 미생물의 길항작용으로 인하여 첨가한 구리가 환원된 황화물과 결합하여 구리에 의한 저해효과는 거의 없는 것으로 나타났다. 구리를 첨가한 경우 초기 프로피온산의 분해가 지연되었으나, 점차 분해되는 경향을 보였으며. 프로피온산의 초산으로의 전환을 고려서 프로피온산의 분해가 초산의 분해 보다 구리의 영향을 많이 받는 것으로 나타났다. 이와 같은 결과를 고려시 구리에 의한 저해효과는 수소이용 메탄균이 초산 이용 메탄균에 비해 보다 민감한 것으로 판단된다.

• Journal of Microbiology and Biotechnology
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• 제24권12호
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• pp.1707-1718
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• 2014

In this study, the phylogenetic diversities of bacterial and archaeal communities in a plant-microbial fuel cell (P-MFC) were investigated together with the environmental parameters, affecting its performance by using rice as a model plant. The beneficial effect of the plant appeared only during a certain period of the rice-growing season, at which point the maximum power density was approximately 3-fold higher with rice plants. The temperature, electrical conductivity (EC), and pH in the cathodic and anodic compartments changed considerably during the rice-growing season, and a higher temperature, reduced difference in pH between the cathodic and anodic compartments, and higher EC were advantageous to the performance of the P-MFC. A 16S rRNA pyrosequencing analysis showed that the 16S rRNAs of Deltaproteobacteria and those of Gammaproteobacteria were enriched on the anodes and the cathodes, respectively, when the electrical circuit was connected. At the species level, the operational taxonomic units (OTUs) related to Rhizobiales, Geobacter, Myxococcus, Deferrisoma, and Desulfobulbus were enriched on the anodes, while an OTU related to Acidiferrobacter thiooxydans occupied the highest proportion on the cathodes and occurred only when the circuit was connected. Furthermore, the connection of the electrical circuit decreased the abundance of 16S rRNAs of acetotrophic methanogens and increased that of hydrogenotrophic methanogens. The control of these physicochemical and microbiological factors is expected to be able to improve the performance of P-MFCs.