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( Harshad Lade ),( Diby Paul ),( Jihyang Kweon ) 한국미생물 · 생명공학회 2015 Journal of microbiology and biotechnology Vol.25 No.11
This work investigated the potential of curcumin (CCM) and (-)-epigallocatechin gallate (EGCG) to inhibit N-acyl homoserine lactone (AHL)-mediated biofilm formation in gramnegative bacteria from membrane bioreactor (MBR) activated sludge. The minimum inhibitory concentrations (MICs) of CCM alone against all the tested bacteria were 200-350 μg/ml, whereas those for EGCG were 300-600 μg/ml. Biofilm formation at one-half MICs indicated that CCM and EGCG alone respectively inhibited 52-68% and 59-78% of biofilm formation among all the tested bacteria. However, their combination resulted in 95-99% of biofilm reduction. Quorum sensing inhibition (QSI) assay with known biosensor strains demonstrated that CCM inhibited the expression of C4 and C6 homoserine lactones (HSLs)-mediated phenotypes, whereas EGCG inhibited C4, C6, and C10 HSLs-based phenotypes. The Center for Disease Control biofilm reactor containing a multispecies culture of nine bacteria with onehalf MIC of CCM (150 μg/ml) and EGCG (275 μg/ml) showed 17 and 14 μg/cm2 of extracellular polymeric substances (EPS) on polyvinylidene fluoride membrane surface, whereas their combination (100 μg/ml of each) exhibited much lower EPS content (3 μg/cm2). Confocal laser scanning microscopy observations also illustrated that the combination of compounds tremendously reduced the biofilm thickness. The combined effect of CCM with EGCG clearly reveals for the first time the enhanced inhibition of AHL-mediated biofilm formation in bacteria from activated sludge. Thus, such combined natural QSI approach could be used for the inhibition of membrane biofouling in MBRs treating wastewaters.
Lade, Harshad,Paul, Diby,Kweon, Ji Hyang Molecular Diversity Preservation International (MD 2014 INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES Vol.15 No.2
<P>The formation of biofilm in a membrane bioreactor depends on the production of various signaling molecules like <I>N</I>-acyl homoserine lactones (AHLs). In the present study, a total of 200 bacterial strains were isolated from membrane bioreactor activated sludge and screened for AHLs production using two biosensor systems, <I>Chromobacterium violaceum</I> CV026 and <I>Agrobacterium tumefaciens</I> A136. A correlation between AHLs production and biofilm formation has been made among screened AHLs producing strains. The 16S rRNA gene sequence analysis revealed the dominance of <I>Aeromonas</I> and <I>Enterobacter sp</I>. in AHLs production; however few a species of <I>Serratia</I>, <I>Leclercia</I>, <I>Pseudomonas</I>, <I>Klebsiella</I>, <I>Raoultella</I> and <I>Citrobacte</I>r were also identified. The chromatographic characterization of sludge extract showed the presence of a broad range of quorum sensing signal molecules. Further identification of sludge AHLs by thin layer chromatography bioassay and high performance liquid chromatography confirms the presence of C4-HSL, C6-HSL, C8-HSL, 3-oxo-C8-HSL, C10-HSL, C12-HSL, 3-oxo-C12-HSL and C14-HSL. The occurrence of AHLs in sludge extract and dominance of <I>Aeromonas</I> and <I>Enterobacter sp.</I> in activated sludge suggests the key role of these bacterial strains in AHLs production and thereby membrane fouling.</P>
Effects of N-acetylcysteine on biofilm formation by MBR sludge
Song, WonJung,Lade, Harshad,Yu, YoungJae,Kweon, JiHyang Techno-Press 2018 Membrane Water Treatment Vol.9 No.3
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.
Nam, AnNa,Kweon, JiHyang,Ryu, JunHee,Lade, Harshad,Lee, ChungHak Techno-Press 2015 Membrane Water Treatment Vol.6 No.3
Membrane biofouling impedes wide application of membrane bioreactor (MBR) for wastewater treatment. Recently, quorum sensing (QS) mechanisms are accounted for one of major mechanisms in biofouling of MBRs. In this study, vanillin was applied to investigate reduction of biofouling in MBRs. MBR sludge was analyzed to contain QS signal molecules by cross-feeding biosensor assay and HPLC. In addition, the inhibitory activity of vanillin against bacterial quorum sensing was verified using an indicator strain CV026. The vanillin doses greater than 125 mg/L to 100 mL of MBR sludge showed 25% reduction of biofilm formed on the membrane surfaces. Two MBRs, i.e., a typical MBR as a control and an MBR with vanillin, were operated. The TMP increases of the control MBR were more rapid compared to those of the MBR with the vanillin dose of 250 mg/L. The treatment efficiencies of the two MBRs on organic removal and MLSS were maintained relatively constant. Extracellular polymeric substance concentrations measured at the end of the MBR operation were 173 mg/g biocake for the control MBR and 119 mg/g biocake for the MBR with vanillin. Vanillin shows great potential as an anti-biofouling agent for MBRs without any interference on microbial activity for wastewater treatment.