• 한국지하수토양환경학회지:지하수토양환경
• /
• 제14권6호
• /
• pp.45-52
• /
• 2009

나프탈렌 분해균주인 Pseudomonas aeruginosa CZ6을 오염된 토양에서 분리하였으며 분리된 균주는 결정상태의 나프탈렌에 부착하고 그 주변에 extracellular polymeric substance를 분비하는 특성을 가졌다. LB, YM과 MSM 배지를 사용하여 배지의 종류에 따른 biofilm 생성량을 측정한 결과, LB 배지에서 biofilm이 가장 많이 생성되는 것으로 나타났다. 나프탈렌을 기질로 한 배양조건에서 균주는 기질의 농도 영향을 크게 받지 않고 0.10% 기질, 150 rpm 조건에서 최적 배양조건은 $30^{\circ}C$, pH 7로 나타났다. 두 가지 토양에서 배지의 종류에 따른 나프탈렌의 분해특성을 관찰한 결과 초기에는 MSM 배지에서 나프탈렌이 가장 많이 분해가 되었다. 그러나 생물이용성이 제한을 받는 조건에서 LB 배지의 나프탈렌이 가장 빨리 제거가 되었다. 이런 결과는 biofilm의 형성과 extracellular polymeric substance 생성이 토양에 흡착된 잔류 나프탈렌의 생물학적 이용성을 향상시키기 때문인 것으로 사료된다.

• 한국물환경학회지
• /
• 제36권3호
• /
• pp.185-193
• /
• 2020

Bimodal flocculation describes the aggregation and breakage processes of the flocculi (or primary particles) and the flocs in the water environment. Bimodal flocculation causes bimodal size distribution with the two separate peaks of the flocculi and the flocs. Extracellular polymeric substances and ionic species common in the water environment increase the occurrence of bimodal flocculation and flocculi-floc size distribution, under the flocculation mechanisms of electrostatic attraction and polymeric bridging. This study investigated bimodal flocculation and flocculi-floc size distribution, with respect to the extracellular polymeric substance concentration and ionic strength in the kaolinite-containing suspension. The batch flocculation tests comprising 0.12 g/L of kaolinite showed that the highest flocculation potential occurred at the lowest xanthan gum (as extracellular polymeric substances) concentration, under all the ionic strengths of 0.001, 0.01, and 0.1 M NaCl. Also, it was important to note that the higher ionic strength resulted in the higher flocculation potential, at all the xanthan gum concentrations. The bimodal flocculation and flocculi-floc size distribution became apparent in the experimental conditions, which had low and intermediate flocculation potential. Besides the polymeric bridging flocculation, steric stabilization increased the flocculi mass fraction against the floc mass fraction, thereby developing the bimodal size distribution.

• 상하수도학회지
• /
• 제35권1호
• /
• pp.63-69
• /
• 2021

Microalgae are primary producers of aquatic ecosystems, securing biodiversity and health of the ecosystem and contributing to reducing the impact of climate change through carbon dioxide fixation. Also, they are useful biomass that can be used as biological resources for producing valuable industrial products. However, harvesting process, which is the separation of microalgal biomass from mixed liquor, is an important bottleneck in use of valorization of microalgae as a bioresource accounting for 20 to 30% of the total production cost. This study investigates the applicability of sewage sludge-derived extracellular polymeric substance (EPS) as bioflucculant for harvesting microalgae. We compared the flocculation characteristics of microalgae using EPSs extracted from sewage sludge by three methods. The flocculation efficiency of microalgae is closely related to the carbohydrate and protein concentrations of EPS. Heat-extracted EPS contains the highest carbohydrate and protein concentrations and can be a best-suited bioflocculant for microalgae recovery with 87.2% flocculation efficiency. Injection of bioflocculant improved the flocculation efficiency of all three different algal strains, Chlorella Vulgaris, Chlamydomonas Asymmetrica, Scenedesmus sp., however the improvement was more significant when it was used for flocculation of Chlamydomonas Asymmetrica with flagella.

• Environmental Engineering Research
• /
• 제15권1호
• /
• pp.3-7
• /
• 2010

To better understand the ecology of tetrade forming organisms (TFOs) floating in a large amount of dairy wastewater treatment plant (WWTP) effluent (sequencing batch reactor [SBR]) during the inefficient phosphorus (P) removal process of an enhanced biological P removal system, the TFOs from the effluent of a full scale WWTP were separated and attempts made to culture the TFOs in presence/absence of oxygen. The intact TFOs only grew aerobically in the form of unicellular short-rods. Furthermore, to identify the intact TFOs and unicellular short-rods the DNAs of both were extracted, analyzed using their denaturing gradient gel electrophoresis (DGGE)-profiles and then sequenced. The TFOs and unicellular short-rods exhibited the same banding pattern in their DGGE-profiles, and those sequencing data resulted in their identification as Acinetobacter sp. The intact TFOs appeared in clumps and packages of tetrade cells, and were identified as Acinetobacter sp., which are known as strict aerobes and efficient P-removers. The thick layer of extracellular polymeric substance surrounding Acinetobacter sp. may inhibit phosphate uptake, and the cell morphology of TFOs might subsequently be connected with their survival strategy under the anaerobic regime of the SBR system.

• Bulletin of the Korean Chemical Society
• /
• 제32권10호
• /
• pp.3726-3729
• /
• 2011

Biofilm formation is inevitable in a bioelectrochemical system in which microorganisms act as a sole biocatalyst. Cathodic biofilm (CBF) works as a double-edged sword in the performance of the air-cathode microbial fuel cells (MFCs). Proton and oxygen crossover through the CBF are limited by the robust structure of extracellular polymeric substances, composition of available constituents and environmental condition from which the biofilm is formed. The MFC performance in terms of power, current and coulombic efficiency is influenced by the nature and origin of CBF. Development of CBF from different ecological environment while keeping the same anode inoculums, contributes additional charge transfer resistance to the total internal resistance, with increase in coulombic efficiency at the expense of power reduction. This study demonstrates that MFC operation conditions need to be optimized on the choice of initial inoculum medium that leads to the biofilm formation on the air cathode.

• Journal of Microbiology and Biotechnology
• /
• 제28권1호
• /
• pp.77-86
• /
• 2018

The human pathogen and food spoiler Bacillus cereus can form biofilms that act as a persistent source of contamination, which is of public health concern. This study aimed to understand how the source of isolation might affect the behavior of biofilm formation. Biofilm formation abilities of 56 strains of B. cereus isolated from different environments, including human food poisoning, farm, and food, were determined. Crystal violet assay results revealed significant (p < 0.05) differences in biofilm formation abilities among the strains isolated from different sources only at an early stage of incubation. However, strain origin showed no impact on later stage of biofilm formation. Next, correlation of the group of isolates on the basis of their biofilm-forming abilities with the number of sessile cells, sporulation, and extracellular polymeric substance (EPS) formation was determined. The number of sessile cells and spores in biofilms was greatly influenced by the groups of isolates that formed dense, moderate, and weak biofilms. The contribution of extracellular DNA and/or proteins to EPS formation was also positively correlated with biofilm formation abilities. Our results that the source of isolation had significant impact on biofilm formation might provide important information to develop strategies to control B. cereus biofilm formation.

• Biotechnology and Bioprocess Engineering:BBE
• /
• 제5권6호
• /
• pp.460-464
• /
• 2000

Extracellular polymeric substances (EPS) are believed to play a role in the binding and formation of microbial flocs. However, the precise role is not well known. Sludge settling characteristics and the carbohydrate to protein ratio in EPS were tested with various airflow rates in this study. Sludge was collected from three modified sequencing batch reactors (SBRs), which were operated at 16$\^{C}$ with an airflow rate of 0.8L/min, 3L/min and 6L/min, respectively. During the operation, the reactor operated at an airflow rate of 0.8L/min showed sludge volume index (SVI) of 80 to 90ml/g and a constant ratio of carbohydrate to protein in the EPS, while a significant increase in the SVI was seen in the other reactors. Sludge bulking increased the amount of carbohydrate in the EPS, while kept protein almost constant in the airflow rate of 3L/min ad 6L/min. Surface charge also increased with increases in the carbohydrate to protein ratio in the EPS, which weakens the attraction between the EPS and multivalent cations. The ratio of carbohydrate to protein in the EPS was tween the EPS and multivalent cations. The ratio of carbohydrate to protein in the EPS was inferred to be essential for bioflocculation.

• Membrane and Water Treatment
• /
• 제9권3호
• /
• pp.195-203
• /
• 2018

N-acetylcysteine (NAC) has been widely used as an initial mucolytic agent and is generally used as an antioxidant to help alleviate various inflammatory symptoms. NAC reduces bacterial extracellular polymeric substances (EPS) production, bacterial adhesion to the surface and strength of mature biofilm. The efficacy has been shown to inhibit proliferation of gram-positive and gram-negative bacteria. In membrane bioreactor (MBR) processes, which contain a variety of gram negative bacteria, biofilm formation has become a serious problem in stable operation. In this study, use of NAC as an inhibitor of biofilm contamination was investigated using the center for disease control (CDC) reactors with MBR sludge. Biomass reduction was confirmed with CLSM images of membrane surfaces by addition of NAC, which was more efficient as the concentration of NAC was increased to 1.5 mg/mL. NAC addition also showed decreases in EPS concentrations of the preformed biofilm, indicating that NAC was able to degrade EPS in the mature biofilm. NAC addition was also effective to inhibit biofilm formation by MBR sludge, which consisted of various microorganisms in consortia.

• Membrane and Water Treatment
• /
• 제10권5호
• /
• pp.331-338
• /
• 2019

This study aimed to investigate the membrane fouling and sludge characteristics in a pilot-scale submerged membrane bioreactor (MBR) operated under low temperature ($7^{\circ}C$). To elucidate the mechanisms of membrane fouling at low temperature, we studied the correlation between MBR performances and physicochemical properties of sludge including extracellular polymeric substance (EPS), relative hydrophobicity (RH) and floc size during long-term operation. The MBR was shown able to remove chemical oxygen demand (COD) stably and efficiently (>90 %) in the case of overgrowth of filamentous bacteria (bulking sludge) at low temperature. On the other hand, the occurrence of filamentous bulking greatly accelerated membrane fouling, as indicated by membrane filtration period of 14 days for filamentous bulking at $7^{\circ}C$, in comparison with that of 27 days for non-bulking sludge at $24^{\circ}C$ The overgrowth of filamentous bacteria resulting from low-temperature condition led to an increased release of EPS, higher RH, smaller floc size and lower fractal dimension of sludge. These factors accelerated the formation of compact cake layer on membrane surface in association with performance diminution in terms of increase in transmembrane pressure (TMP) of the membrane and thus the decrease in membrane permeability.

• 대한환경공학회지
• /
• 제22권2호
• /
• pp.323-329
• /
• 2000

막결합형 활성슬러지 공정은 막오염으로 인한 플럭스 감소 때문에 시스템의 경제성과 효율성이 떨어지는 문제점을 지니고 있어 막오염에 대한 체계적인 연구가 요구되고 있다. 따라서 본 연구에서는 한외여과막과 결합된 활성슬러지 시스템을 운영하면서 막오염 유발 인자를 규명하고자 하였다. 활성슬러지 공정의 운전 초기에 급격한 플록 크기 감소와 동시에 급격한 플럭스 감소가 관찰되었다. 초기 플럭스 감소현상은 활성슬러지 플록의 입자 크기 감소로 인한 케이크 저항의 증가가 주요 원인이었다. 이것은 운전시간에 따른 각 여과 저항값을 측정하여 확인하였다. 또한, 플록 해체로 인하여 EPS 양이 운전 전보다 약 150 % 가량 증가한 것을 볼 때 EPS 양의 증가가 케이크 저항 증가의 또 다른 원인이 될 수 있음을 제시하였다.