• Journal of Microbiology and Biotechnology
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• v.24 no.1
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• pp.97-105
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• 2014

Quorum quenching (QQ) with a microbial vessel has recently been reported as an economically feasible biofouling control platform in a membrane bioreactor (MBR) for wastewater treatment. In this study, a quorum quenching MBR with a ceramic microbial vessel (CMV) was designed to overcome the extremely low F/M ratio inside a microbial vessel. The CMV was prepared with a monolithic ceramic microporous membrane and AHL-degrading QQ bacteria, Pseudomonas sp. 1A1. The "inner flow feeding mode" was introduced, under which fresh feed was supplied to the MBR only through the center lumen in the CMV. The inner flow feeding mode facilitated nutrient transport to QQ bacteria in the CMV and thus enabled relatively long-term maintenance of cell viability. The quorum quenching effect of the CMV on controlling membrane biofouling in the MBR was more pronounced with the inner flow feeding mode, which was identified by the slower increase in the transmembrane pressure as well as by the visual observation of a biocake that formed on the used membrane surface. In the QQ MBR with the CMV, the concentrations of extracellular polymeric substances were substantially decreased in the biocake on the membrane surface compared with those in the conventional MBR. The CMV also showed its potential with effective biofouling control over long-term operation of the QQ MBR.

• Advances in nano research
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• v.8 no.2
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• pp.183-190
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• 2020

The objectives of this research were the reduction of membrane fouling and improvement of sludge properties by using synthesized H-ZSM-5 and NH₄-ZSM-5 zeolites. These two nano zeolites were synthesized and added to the membrane bioreactor (MBR). Three similar MBRs with the same operational condition were used in order to evaluate their effect on the mentioned matters. The evaluated parameters were trans-membrane pressure (TMP), Fourier-transform infrared spectroscopy (FTIR), particle size distribution (PSD), soluble microbial product (SMP), extracellular polymeric substances (EPS) and, excitation-emission matrix (EEM). The MBR₀ was without any additional zeolite while 0.4 g/L of H-ZSM-5 and NH₄-ZSM-5 were added to MBR_HZSM-5 and MBR_NH4ZSM-5, respectively. The COD removal of the MBR₀, MBR_H-ZSM-5 and MBR_NH4-ZSM-5 were 87.5%, 93.3% and 94.6%, respectively. The TMP of the MBR_H-ZSM-5 was 45% less than MBR₀ whereas the reduction for MBR_NH4-ZSM-5 was 65.5%. Also results showed that both H-ZSM-5 and NH₄-ZSM-5 caused reduction in protein and polysaccharide related EPS but the NH₄-ZSM-5 had better performance toward the elimination of organic compounds.

• Korean Journal of Microbiology
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• v.52 no.2
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• pp.183-191
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• 2016

Marine bacteria have represented unique physiologies and products which are not discovered from terrestrial organisms. There has been great interest to utilize and develop marine bacteria in many industrial sectors. Recently, we isolated and characterized anaerobic bacteria from various marine environments in Korea to search organic acids fermenting strains. From our enrichment performed under anaerobic condition, 65 strains were isolated and identified by the 16S rRNA gene sequence analysis. Among them, eleven strains were selected for phylogenetical and biochemical analysis. All tested strains were affiliated with Class Clostridia except one with Class Bacteroidia. Most of strains produce acetate (6 strains) with butyrate (2 strains) and/or formate (4 strains). Strain MCWD5 transformed 40% of glucose to extracellular polymeric substances. These results indicate that many novel anaerobic microorganisms which have great potential in commercial application are distributed in the marine environments of Korean Peninsula.

• Journal of Microbiology and Biotechnology
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• v.26 no.8
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• pp.1428-1438
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• 2016

In the present work, Arthrobacter sp. 25, a lead-tolerant bacterium, was assayed to remove lead(II) from aqueous solution. The biosorption process was optimized by response surface methodology (RSM) based on the Box-Behnken design. The relationships between dependent and independent variables were quantitatively determined by second-order polynomial equation and 3D response surface plots. The biosorption mechanism was explored by characterization of the biosorbent before and after biosorption using atomic force microscopy (AFM), scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. The results showed that the maximum adsorption capacity of 9.6 mg/g was obtained at the initial lead ion concentration of 108.79 mg/l, pH value of 5.75, and biosorbent dosage of 9.9 g/l (fresh weight), which was close to the theoretically expected value of 9.88 mg/g. Arthrobacter sp. 25 is an ellipsoidal-shaped bacterium covered with extracellular polymeric substances. The biosorption mechanism involved physical adsorption and microprecipitation as well as ion exchange, and functional groups such as phosphoryl, hydroxyl, amino, amide, carbonyl, and phosphate groups played vital roles in adsorption. The results indicate that Arthrobacter sp. 25 may be potentially used as a biosorbent for low-concentration lead(II) removal from wastewater.

• Food Science of Animal Resources
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• v.42 no.1
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• pp.84-97
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• 2022

We evaluated the anti-biofilm formation and anti-inflammatory activity of Hovenia monofloral honey (HMH) against Enterococcus faecalis. Co-culture of HMH with E. faecalis attenuated the biofilm formation of E. faecalis on a polystyrene surface. In addition, HMH effectively eradicated the established E. faecalis biofilm. HMH significantly attenuated E. faecalis growth but did not affect the production of extracellular polymeric substances on E. faecalis, indicating that reduction of E. faecalis biofilm is a result of HMH-mediated killing of E. faecalis. Furthermore, we found that HMH can effectively attenuate E. faecalis-induced expression of a proinflammatory interleukin-8 (IL- 8) in HT-29 cells. Interestingly, treatment of HMH significantly attenuated the E. faecalis-mediated expression of Toll-like receptor-2 (TLR-2) and its adaptor molecules, myeloid differentiation primary response 88 (MyD88), in HT-29 cells. In addition, E. faecalis-induced mitogen-activated protein kinases (MAPKs) phosphorylation was significantly attenuated by HMH administration. Furthermore, HMH-mediated antiinflammatory efficacy (0.2 mg/mL of HMHs) had an equal extent of inhibitory efficacy as 5 μM of MyD88 inhibitor to attenuate E. faecalis-mediated IL-8 expression in HT-29 cells. These results suggest that HMH could effectively inhibit E. faecalis-mediated gastrointestinal inflammation through regulating the TLR-2/MyD88/MAPKs signaling pathways. Collectively, our data suggest that HMH could be developed as a potential natural agent to control E. faecalis-mediated biofilm formation and inflammation.

• Journal of Korean Society on Water Environment
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• v.39 no.2
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• pp.175-180
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• 2023

The aim of this study was to compare the fouling characteristics of Extracellular polymeric substances (EPS) secreted by Chlorella vulgaris with the case of Bacterial-MBR (BMBR), Microalgal-MBR (MMBR) for advanced wastewater treatment using the Laboratory scale, in order to suggest a method to minimize fouling in MMBR by identifying the effects of amounts and compositions of EPS secreted by C. vulgaris and bacteria in the activated sludge on fouling. Contrary to expectations, fouling occurred relatively severely in the MMBR from the beginning of the operation than in the BMBR. Reasons for such a fouling pattern were considered to be the effect of C-EPS, which accumulates on the membrane surface of MMBR 30 times more than that on the membrane surface of activated sludge (BMBR). In this respect, according to the results of this experiment and a comparative review of several previous studies, it was confirmed that unlike activated sludge, in which the ratio of P-EPS was relatively higher than that of C-EPS, in case of C. vulgaris, the ratio of C-EPS to P-EPS was relatively higher than that in case of activated sludge. This was presumed to be the main cause of the significant fouling phenomenon in MMBR. However, an increase in TMP with increasing C-EPS concentration was not observed.

• Journal of Korean Society of Environmental Engineers
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• v.30 no.8
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• pp.789-797
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• 2008

This study was conducted to investigate removal characteristics of gaseous trimethylamine(TMA) through biofilter packed with waste tire-chips. The sludge in this experiment was collected from an activated sludge operated in a wastewater treatment facility treating malodorous pollutants. The nominal amount of collected sludge was inoculated through packing materials in the filter. The removal efficiencies for varying concentrations and SVs(Space velocity) were assessed based on TMA, COD$_{Cr}$, NO$_3{^-}$-N, NO$_2{^-}$-N, NH$_4{^+}$-N and EPS(Extracellular Polymeric Substances) in leachate, since biofilter had been steady-stately operated. The influent concentration of 10 ppm of TMA was removed to approximately 95% regardless of changing SV at 120 and 180 hr$^{-1}$, but it was lowered to 80 to 90% at SV 240 hr$^{-1}$. As influent concentration was gradually increased from 5 to 55 ppm, the removal efficiencies of TMA were initially high for 95% in the range of 5 to 10 ppm, but lowered to 80% for 10 to 30 ppm. As a part of kinetic study for TMA decomposition, V$_m$(maximum substrate removal rate) and $K_s$(substrate infinity coefficient) were 14.3 g$\cdot$m$^{-3}$$\cdot$h$^{-1}$ and 0.043 g$\cdot$m$^{-3}$, respectively while adapted period was shown in the range of 100 to 150 hr. Also, the EPS concentration was consistently observed from the leachate showing 100 to 200 ppm, which indicates that biofilm has been continuously formed and sustained throughout tire-chips packed reactor.

• Proceedings of the Korea Water Resources Association Conference
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• 2006.05a
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• pp.1415-1419
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• 2006

메탄을 탄소원 및 에너지원으로 이용하는 메탄산화균은 물질대사과정 중에 다량의 세포외 고분자물질인 Extracellular polymeric substances(EPS)를 생성하는데, EPS는 카르복실기와 같은 표면흡착 기능을 가지고 있어 생체흡착제로 사용이 가능하다. 따라서 본 연구에서는 메탄산화세균을 이용하여 중금속인 Cd의 흡착성능을 파악하여 활성슬러지의 흡착능과 비교하고, EPS 농도별, pH별 흡착량의 변화를 실험한 후 Freundlich 흡착모델식에 적용하여 흡착공정의 기본적인 설계인자를 도출하고자 하였다. 실험에 사용한 메탄산화세균은 매립지 복토층 상부 토양에서 분리하여 실험실에서 대량으로 배양하였으며, EPS 생성을 위해 메탄을 Head space의 20%를 주입하고 $30^{\circ}C$, 150rpm에서 질소원이 부족한 조건으로 48hr 동안 배양하였다. Cd의 흡착실험은 용액의 pH를 3에서 8까지 변화를 주면서 활성슬러지와 메탄산화세균의 시간별 흡착능을 측정하였다. 또한 중금속의 농도별 흡착능을 측정하여 흡착평형 상수를 파악하였으며, 중금속 흡착 전, 후 미생물의 SEM 촬영, FT-IR 분석, 전자현미분석(EPMA)을 통하여 무기성분 분석 및 표면관찰을 수행하였다. 실험결과 메탄산화세균에 의해 생성된 EPS 물질은 중금속에 대한 강한 결합능력이 있으며, Cd에 대한 최고 흡착능은 26mg Cd(Ⅱ)/g VSS의 값을 보였다. 이러한 미생물의 EPS의 흡착능은 pH와 칼슘이온의 영향을 많이 받았으며, 메탄산화세균의 FT-IR 분석결과 EPS에는 sulfate ester, pyruvate 등과 같은 작용기와 amino sugar, carboxyl 작용기들이 많이 존재하여 활성슬러지에 비해 중금속의 흡착능이 높은 것으로 사료되었다.X>${\mu}_{max,A}$는 최대암모니아 섭취률을 이용하여 구한 결과 $0.65d^{-1}$로 나타났다.EX>$60%{\sim}87%$가 수심 10m 이내에 분포하였고, 녹조강과 남조강이 우점하는 하절기에는 5m 이내에 주로 분포하였다. 취수탑 지점의 수심이 연중 $25{\sim}35m$를 유지하는 H호의 경우 간헐식 폭기장치를 가동하는 기간은 물론 그 외 기간에도 취수구의 심도를 표층 10m 이하로 유지 할 경우 전체 조류 유입량을 60% 이상 저감할 수 있을 것으로 조사되었다.심볼 및 색채 디자인 등의 작업이 수반되어야 하며, 이들을 고려한 인터넷용 GIS기본도를 신규 제작한다. 상습침수지구와 관련된 각종 GIS데이타와 각 기관이 보유하고 있는 공공정보 가운데 공간정보와 연계되어야 하는 자료를 인터넷 GIS를 이용하여 효율적으로 관리하기 위해서는 단계별 구축전략이 필요하다. 따라서 본 논문에서는 인터넷 GIS를 이용하여 상습침수구역관련 정보를 검색, 처리 및 분석할 수 있는 상습침수 구역 종합정보화 시스템을 구축토록 하였다.N, 항목에서 보 상류가 높게 나타났으나, 철거되지 않은 검전보나 안양대교보에 비해 그 차이가 크지 않은 것으로 나타났다.의 기상변화가 자발성 기흉 발생에 영향을 미친다고 추론할 수 있었다. 향후 본 연구에서 추론된 기상변화와 기흉 발생과의 인과관계를 확인하고 좀 더 구체화하기 위한 연구가 필요할 것이다.게 이루어질 수 있을 것으로 기대된다.는 초과수익률이 상승하지만, 이후로는 감소하므로, 반전거래전략을 활용하는 경우 주식투자기간은 24개월이하의 중단기가 적합함을 발견하였다. 이상의 행태적 측면과 투자성과측면의 실증결과를 통하여 한국주식시장에 있어서 시장수익률을 평균적으로 초과할 수 있는 거래전

• Microbiology and Biotechnology Letters
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• v.40 no.2
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• pp.83-91
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• 2012

Quorum sensing (QS) is a cell-to-cell communication system, which is used by many bacteria to regulate diverse gene expression in response to changes in population density. Bacteria recognize the differences in cell density by sensing the concentration of signal molecules such as N-acyl-homoserine lactones (AHL) and autoinducer-2 (AI-2). In particular, QS plays a key role in biofilm formation, which is a specific bacterial group behavior. Biofilms are dense aggregates of packed microbial communities that grow on surfaces, and are embedded in a self-produced matrix of extracellular polymeric substances (EPS). QS regulates biofilm dispersal as well as the production of EPS. In some bacteria, biofilm formations are regulated by c-di-GMP-mediated signaling as well as QS, thus the two signaling systems are mutually connected. Biofilms are one of the major virulence factors in pathogenic bacteria. In addition, they cause numerous problems in industrial fields, such as the biofouling of pipes, tanks and membrane bioreactors (MBR). Therefore, the interference of QS, referred to as quorum quenching (QQ) has received a great deal of attention. To inhibit biofilm formation, several strategies to disrupt bacterial QS have been reported, and many enzymes which can degrade or modify the signal molecule AHL have been studied. QQ enzymes, such as AHL-lactonase, AHL-acylase, and oxidoreductases may offer great potential for the effective control of biofilm formation and membrane biofouling in the future. This review describes the process of bacterial QS, biofilm formation, and the close relationship between them. Finally, QQ enzymes and their applications for the reduction of biofouling are also discussed.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.8 no.3
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• pp.627-631
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• 2007

The factors affecting on sludge sedimentation are reported as F/M ratio, ingredient, composition of influent substrate, dissolved oxygen concentration, temperature, pH, filamentous bacteria and SRT. Aeration tank applying Bacillus sp. has an important role for maintaining the dominant microorganism species to make steady progress for spore growth affecting sedimentation. This research aims to investigate the affecting factor for the sedimentation in B3 system and RABC system with aeration tank applying tapered aeration. Extracellular polymeric substances(EPS), protein and carbohydrate can be produced for the extreme condition, that is down to 0.2 mg/L of dissolved oxygen in the aeration tank. This research found out the relation between the sedimentation and the EPS production, especially the ratio of protein/carbohydrate. The spore of Bacillus sp. was formed at the low DO then microorganisms produced EPS. The results showed that the production of EPS was 109.95 mgEPS/gSS at 1.6 mg/L of DO, however it was 131.77 mgEPS/gSS at 0.5 mg/L of DO. The sedimentation was affected by protein content in EPS and the ratio of protein and carbohydrate. The settleability of sludge was not affected by the ratio of protein/carbohydrate in B3 process, meanwhile settleability was affected by the ratio of it in RABC process, respectively.