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Lee, Kibaek,Lee, Seonki,Lee, Sang Hyun,Kim, Sang-Ryoung,Oh, Hyun-Suk,Park, Pyung-Kyu,Choo, Kwang-Ho,Kim, Yea-Won,Lee, Jung-Kee,Lee, Chung-Hak American Chemical Society 2016 Environmental science & technology Vol.50 No.20
<P>In the last 30 years, the use of membrane bioreactors (MBRs) for advanced wastewater treatment and reuse have been expanded continuously, but they still suffer from excessive energy consumption resulting from the intrinsic problem of membrane biofouling. One of the major causes of biofouling in MBRs is bacterial quorum sensing (QS) via N-acylhomoserine lactones (AHLs) and/or autoinducer-2 (AI-2), enabling intra- and interspecies communications, respectively. In this study, we demonstrate that farnesol can substantially mitigate membrane biofouling in a MBR due to its quorum quenching (QQ) activity. When Candida albicans (a farnesol producing fungus) entrapping polymer beads (AEBs) were placed in the MBR, the rate of transmembrane pressure (TMP) rise-up was substantially decreased, even for lower aeration intensities. This finding corresponds to a specific aeration energy savings of approximately 40% (25% through the physical washing effect and a further 15% through the biological QQ effect of AEBs) compared to conventional MBRs without AEBs. A real-time RT-qPCR analysis revealed that farnesol secreted from C. albicans mitigated the biofilm formation in MBRs via the suppression of AI-2 QS. Successful control of biofouling and energy savings through fungal-to-bacterial QQ could be expanded to the plant scale for MBRs in wastewater treatment with economic feasibility.</P>
Lee, Kibaek,Kim, Yea-Won,Lee, Seonki,Lee, Sang Hyun,Nahm, Chang Hyun,Kwon, Hyeokpil,Park, Pyung-Kyu,Choo, Kwang-Ho,Koyuncu, Ismail,Drews, Anja,Lee, Chung-Hak,Lee, Jung-Kee American Chemical Society 2018 Environmental science & technology Vol.52 No.11
<P>Bacterial quorum quenching (QQ) by means of degrading signaling molecules has been applied to antibiofouling strategies in a membrane bioreactor (MBR) for wastewater treatment. However, the target signaling molecules have been limited to <I>N</I>-acyl homoserine lactones participating in intraspecies quorum sensing. Here, an approach to disrupting autoinducer-2 (AI-2) signaling molecules participating in interspecies quorum sensing was pursued as a next-generation antibiofouling strategy in an MBR for wastewater treatment. We isolated an indigenous QQ bacterium (<I>Acinetobacter</I> sp. DKY-1) that can attenuate the expression of the quorum-sensing (QS) response through the inactivation of an autoinducer-2 signaling molecule, 4,5-dihydroxy-2,3-pentanedione (DPD), among four kinds of autoinducer-2 QS bacteria. DKY-1 released AI-2 QQ compounds, which were verified to be hydrophilic with a molecular weight of <400 Da. The addition of DKY-1 entrapping beads into an MBR significantly decreased DPD concentration and remarkably reduced membrane biofouling. This new approach, combining molecular biology with wastewater engineering, could enlarge the range of QQ-MBR for antibiofouling and energy savings in the field of wastewater treatment.</P> [FIG OMISSION]</BR>
( Sang Hyun Lee ),( Seonki Lee ),( Kibaek Lee ),( Chang Hyun Nahm ),( Sung-jun Jo ),( Jaewoo Lee ),( Kwang-ho Choo ),( Jung-kee Lee ),( Chung-hak Lee ),( Pyung-kyu Park ) 한국미생물 · 생명공학회 2017 Journal of microbiology and biotechnology Vol.27 No.3
Quorum quenching (QQ) bacteria entrapped in a polymeric composite hydrogel (QQ medium) have been successfully applied in membrane bioreactors (MBRs) for effective biofouling control. However, in order to bring QQ technology closer to practice, the physical strength and lifetime of QQ media should be improved. In this study, enforcement of physical strength, as well as an extension of the lifetime of a previously reported QQ bacteria entrapping hollow cylinder (QQ-HC), was sought by adding a dehydration procedure following the cross-linking of the polymeric hydrogel by inorganic compounds like Ca<sup>2+</sup> and boric acid. Such prepared medium demonstrated enhanced physical strength possibly through an increased degree of physical cross-linking. As a result, a longer lifetime of QQ-HCs was confirmed, which led to improved biofouling mitigation performance of QQ-HC in an MBR. Furthermore, QQ-HCs stored under dehydrated condition showed higher QQ activity when the storage time lasted more than 90 days owing to enhanced cell viability. In addition, the dormant QQ activity after the dehydration step could be easily restored through reactivation with real wastewater, and the reduced weight of the dehydrated media is expected to make handling and transportation of QQ media highly convenient and economical in practice.
Lee, Seonki,Park, Seung-Kook,Kwon, Hyeokpil,Lee, Sang Hyun,Lee, Kibaek,Nahm, Chang Hyun,Jo, Sung Jun,Oh, Hyun-Suk,Park, Pyung-Kyu,Choo, Kwang-Ho,Lee, Chung-Hak,Yi, Taewoo American Chemical Society 2016 Environmental science & technology Vol.50 No.4
<P>Quorum quenching (QQ) has recently been acknowledged to be a sustainable antifouling strategy and has been investigated widely using lab-scale membrane bioreactor (MBR) systems. This study attempted to bring this QQ-MBR closer to potential practical application. Two types of pilot-scale QQ-MBRs with QQ bacteria entrapping beads (QQ-beads) were installed and run at a wastewater treatment plant, feeding real municipal wastewater to test the systems' effectiveness for membrane fouling control and thus the amount of energy savings, even under harsh environmental conditions. The rate of trans membrane pressure (TMP) build-up was significantly mitigated in QQ-MBR compared to that in a conventional-MBR. Consequently, QQ-MBR can substantially reduce energy consumption by reducing coarse bubble aeration without compromising the effluent water quality. The addition of QQ:beads to a conventional MBR substantially affected the EPS concentrations, as well as microbial floc size in the mixed liquor. Furthermore, the QQ activity and mechanical stability of QQ-beads were well maintained for at least four months, indicating QQ-MBR has good potential for practical applications.</P>
Lee, Sang H.,Lee, Seonki,Lee, Kibaek,Nahm, Chang H.,Kwon, Hyeokpil,Oh, Hyun-Suk,Won, Young-June,Choo, Kwang-Ho,Lee, Chung-Hak,Park, Pyung-Kyu American Chemical Society 2016 Environmental science & technology Vol.50 No.16
<P>Recently, membrane bioreactors (MBRs) with quorum quenching (QQ) bacteria entrapping beads have been reported as a new paradigm in biofouling control because, unlike conventional post-biofilm control methods, bacterial QQ can inhibit biofilm formation through its combined effects of physical scouring of the membrane and inhibition of quorum sensing (QS). In this study, using a special reporter strain (Escherichia coli JB525), the interaction between QS signal molecules and quorum quenching bacteria entrapping beads (QQ-beads) was elucidated through visualization of the QS signal molecules within a QQ-bead using a fluorescence microscope. As a result, under the conditions considered in this study, the surface area of QQ-media was likely to be a dominant parameter in enhancing QQ activity over total mass of entrapped QQ bacteria because QQ bacteria located near the core of a QQ-bead were unable to display their QQ activities. On the basis of this information, a more efficient QQ-medium, a QQ hollow cylinder (QQ-HC), was designed and prepared. In batch experiments, QQ-HCs showed greater QQ activity than QQ:beads as a result of their higher surface area and enhanced physical washing effect because of their larger impact area against the membrane surface. Furthermore, it was shown that such advantages of QQ-HCs resulted in more effective mitigation of membrane fouling than from QQ-beads in lab-scale continuous MBRs.</P>
( Seonki Lee ),( Sang Hyun Lee ),( Kibaek Lee ),( Hyeokpil Kwon ),( Chang Hyun Nahm ),( Chung-hak Lee ),( Pyung-kyu Park ),( Kwang-ho Choo ),( Jung-kee Lee ),( Hyun-suk Oh ) 한국미생물 · 생명공학회 2016 Journal of microbiology and biotechnology Vol.26 No.10
Recently, spherical beads entrapping quorum quenching (QQ) bacteria have been reported as effective moving QQ-media for biofouling control in MBRs for wastewater treatment owing to their combined effects of biological (i.e., quorum quenching) and physical washing. Taking into account both the mass transfer of signal molecules through the QQ-medium and collision efficiencies of the QQ-medium against the filtration membranes in a bioreactor, a cylindrical medium (QQ-cylinder) was developed as a new shape of moving QQ-medium. The QQcylinders were compared with previous QQ-beads in terms of the QQ activity and the physical washing effect under identical loading volumes of each medium in batch tests. It was found that the QQ activity of a QQ-medium was highly dependent on its specific surface area, regardless of the shape of the medium. In contrast, the physical washing effect of a QQmedium was greatly affected by its geometric structure. The enhanced anti-biofouling property of the QQ-cylinders relative to QQ-beads was confirmed in a continuous laboratoryscale MBR with a flat-sheet membrane module.
( Chang Hyun Nahm ),( Seonki Lee ),( Sang Hyun Lee ),( Kibaek Lee ),( Jaewoo Lee ),( Hyeokpil Kwon ),( Kwang-ho Choo ),( Jung-kee Lee ),( Jae Young Jang ),( Chung-hak Lee ),( Pyung-kyu Park ) 한국미생물 · 생명공학회 2017 Journal of microbiology and biotechnology Vol.27 No.3
Biofilm formation on the membrane surface results in the loss of permeability in membrane bioreactors (MBRs) for wastewater treatment. Studies have revealed that cellulose is not only produced by a number of bacterial species but also plays a key role during formation of their biofilm. Hence, in this study, cellulase was introduced to a MBR as a cellulose-induced biofilm control strategy. For practical application of cellulase to MBR, a cellulolytic (i.e., cellulaseproducing) bacterium, Undibacterium sp. DM-1, was isolated from a lab-scale MBR for wastewater treatment. Prior to its application to MBR, it was confirmed that the cell-free supernatant of DM-1 was capable of inhibiting biofilm formation and of detaching the mature biofilm of activated sludge and cellulose-producing bacteria. This suggested that cellulase could be an effective anti-biofouling agent for MBRs used in wastewater treatment. Undibacterium sp. DM-1-entrapping beads (i.e., cellulolytic-beads) were applied to a continuous MBR to mitigate membrane biofouling 2.2-fold, compared with an MBR with vacant-beads as a control. Subsequent analysis of the cellulose content in the biofilm formed on the membrane surface revealed that this mitigation was associated with an approximately 30% reduction in cellulose by cellulolytic-beads in MBR.
Nahm, Chang Hyun,Choi, Dong-Chan,Kwon, Hyeokpil,Lee, Seonki,Lee, Sang Hyun,Lee, Kibaek,Choo, Kwang-Ho,Lee, Jung-Kee,Lee, Chung-Hak,Park, Pyung-Kyu Elsevier 2017 Journal of membrane science Vol.526 No.-
<P><B>Abstract</B></P> <P>Quorum quenching (QQ) has been recognized as an innovative approach for biofouling control in membrane bioreactors (MBRs). Recently, QQ bacteria entrapping beads (QQ-beads) have been developed and verified to have excellent anti-biofouling potential in a pilot-scale MBR with flat-sheet membrane modules. In this study, considering the dense structure of hollow fiber (HF) bundles into which QQ-beads can hardly penetrate, QQ bacteria entrapping sheets (QQ-sheets) were developed as a new shape of QQ-media suitable for MBRs with HF modules. In a lab-scale MBR, QQ-sheets with a thickness of 0.5mm exhibited a greater physical washing effect than did QQ-beads with a diameter of 3.5mm because the former collided with membrane surfaces at the inner as well as the outer part of HF bundles, whereas the latter only made contact with the outer part. Moreover, QQ-sheets showed 2.5-fold greater biological QQ activity than did QQ-beads due to their greater total surface area at a fixed volume of QQ-media. These results suggest high potential for QQ-sheets to be used in MBRs with HF modules.</P> <P><B>Highlights</B></P> <P> <UL> <LI> QQ-sheets were developed to effectively mitigate biofouling in MBR with HF module. </LI> <LI> QQ-sheets effectively detached biofilm on both inner and outer part in HF module. </LI> <LI> QQ-sheets showed greater QQ activity than QQ-beads due to their higher surface area. </LI> <LI> The merits of QQ-sheets were confirmed in lab-scale continuous MBR with a HF module. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Lee, Kibaek,Yu, Huarong,Zhang, Xiaolei,Choo, Kwang-Ho Elsevier 2018 Bioresource technology Vol.270 No.-
<P><B>Abstract</B></P> <P>Membrane biofouling, due to biofilm growth after planktonic bacteria attachment to a membrane, is a major bottleneck limiting the energy-efficient operation and maintenance of membrane bioreactors (MBRs). Microbial communications, known as quorum sensing (QS), are responsible for this biofouling behavior. Novel strategies for stopping this communication, known as quorum quenching (QQ), appear to be successful for biofouling control in MBRs used for wastewater treatment. This review describes recent information regarding the signal molecules and mechanisms responsible for QS behaviors, promising approaches for QQ (enzymatic, bacterial, fungal, photocatalytic, mimicking, and biostimulating methods), and efficient fabrication and use of QQ media for MBR applications. We discuss the opportunities and challenges of QQ techniques for their further improvement and practical use in MBRs.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Membrane bioreactors exhibit unavoidable fouling caused by microbial complexes. </LI> <LI> Microbial chatting is mediated via signaling molecules within and between species. </LI> <LI> Quorum sensing induces biofilm formation leading to membrane biofouling. </LI> <LI> Quorum quenching is a novel, innovative strategy for biofouling control. </LI> <LI> Engineering studies have developed efficient media designs, storage, and doses. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>