“…These AHL were also frequently detected in the past studies. 14,16,24,29 Concentrations of AHL with no substitution in the side chain were higher at most sludge samples.…”
Section: Resultsmentioning
confidence: 95%
“…Recently, MBR sludge is more popular target of AHL analysis. In MBR sludge, C 4 -HSL, C 6 -HSL, C 8 -HSL, and 3O-C 8 -HSL have been detected by HPLC 14,29 and C 6 -HSL, C 8 -HSL, and C 10 -HSL by TLC bioassay. 16 However, concentrations of AHL in activated sludge were not quantified in those studies except by Tan et al, 3 which analyzed supernatant of aerobic granules.…”
Quorum sensing is recently considered to play important roles in biological wastewater treatment processes. This study aimed to investigate diversity of N-acyl homoserine lactones (AHL) among biological wastewater treatment processes and their locations. We analyzed and quantified 10 AHL in activated sludge at wastewater treatment plants (WWTPs) by Fourier transform mass spectrometry (FTMS) and by bioassay on thin-layer chromatography (TLC). Sludge samples were taken at seven WWTPs in Japan and in Thailand, which were chosen to compare different process types including a pilot-scale membrane bioreactor process. Various AHL were detected in activated sludge, suggesting the presence of quorum sensing activity in many practical WWTPs. Detection of AHL by LC-FTMS was much more sensitive than by TLC bioassay, because TLC bioassay was implied to be affected by the presence of quorum quenching molecules in activated sludge. With LC-FTMS analysis, AHL, which has short straight chain in the acyl group, were more abundant. Especially, C 4 -HSL, C 7 -HSL, and C 8 -HSL were detected widely independent of locations and process types. AO processes had higher AHL productivity than other processes.npj Clean Water (2019) 2:11 ; https://doi.
“…These AHL were also frequently detected in the past studies. 14,16,24,29 Concentrations of AHL with no substitution in the side chain were higher at most sludge samples.…”
Section: Resultsmentioning
confidence: 95%
“…Recently, MBR sludge is more popular target of AHL analysis. In MBR sludge, C 4 -HSL, C 6 -HSL, C 8 -HSL, and 3O-C 8 -HSL have been detected by HPLC 14,29 and C 6 -HSL, C 8 -HSL, and C 10 -HSL by TLC bioassay. 16 However, concentrations of AHL in activated sludge were not quantified in those studies except by Tan et al, 3 which analyzed supernatant of aerobic granules.…”
Quorum sensing is recently considered to play important roles in biological wastewater treatment processes. This study aimed to investigate diversity of N-acyl homoserine lactones (AHL) among biological wastewater treatment processes and their locations. We analyzed and quantified 10 AHL in activated sludge at wastewater treatment plants (WWTPs) by Fourier transform mass spectrometry (FTMS) and by bioassay on thin-layer chromatography (TLC). Sludge samples were taken at seven WWTPs in Japan and in Thailand, which were chosen to compare different process types including a pilot-scale membrane bioreactor process. Various AHL were detected in activated sludge, suggesting the presence of quorum sensing activity in many practical WWTPs. Detection of AHL by LC-FTMS was much more sensitive than by TLC bioassay, because TLC bioassay was implied to be affected by the presence of quorum quenching molecules in activated sludge. With LC-FTMS analysis, AHL, which has short straight chain in the acyl group, were more abundant. Especially, C 4 -HSL, C 7 -HSL, and C 8 -HSL were detected widely independent of locations and process types. AO processes had higher AHL productivity than other processes.npj Clean Water (2019) 2:11 ; https://doi.
“…In activated sludge process, sludge exists as flocs, and activated sludge flocs are composed of a highly dense microbial consortium in a matrix of EPS. Quorum sensing (QS) refers to the phenomenon that planktonic bacterial cells may regulate their collective actions in response to environmental challenges through sensing specific chemical molecules (Waheed et al, 2016;Wu et al, 2017). The QS signaling molecules (like N-acyl-L-homoserine lactone, AHL) mediated gene expression is a cell density-dependent gene expression mechanism, and QS may exist in activated sludge flocs since it is a model high-density microbiological community (Huang et al, 2016).…”
Section: Introductionmentioning
confidence: 99%
“…The QS signaling molecules (like N-acyl-L-homoserine lactone, AHL) mediated gene expression is a cell density-dependent gene expression mechanism, and QS may exist in activated sludge flocs since it is a model high-density microbiological community (Huang et al, 2016). Previous studies have reported the existence of AHLs and AHLs-producing microorganisms in activated sludge flocs (Valle et al, 2004;Chong et al, 2012;Lv et al, 2014;Waheed et al, 2016;. QS in monospecies biofilms was shown to regulate different aspects of biofilm formations, maturation and distribution of EPS (Wu et al, 2017), such as surface colonization by cell motility, biofilm thickness, the formation of bacterial clusters or structurally homogeneous biofilms, and overall biofilm depth and architecture (Solano et al, 2014).…”
The deterioration of sludge settleability is a common problem in sludge reduction systems with metabolic uncouplers (MUs). The deterioration mechanisms were studied by conducting laboratory-based tests for 85 days. The sludge volume index (SVI 30) increased from 88.0 mL/g SS to 149.5e158.9 mL/g SS with MUs. The addition of MUs decreased the N-acyl-L-homoserine lactone (AHLs) content of the sludge by increasing the AHL-degrading bacteria (Paenibacillus spp., Bacillus spp. and Microbacterium sp.) and decreasing or eliminating the AHL-producing bacteria (Paracoccus sp.). Meanwhile, the addition of MUs increased the extracellular polymeric substances (EPS) of sludge and decreased its proteinpolysaccharide ratio (PN/PS). The decrease of AHL content and the changes of EPS resulted in the deterioration of sludge settleability in the MUs systems. The statistical analysis suggested the decrease of AHL content was more important than the change of sludge EPS on deteriorate the sludge settleability.
“…In MBRs, the Gram-negative proteobacteria phylum was demonstrated to be the most abundant among the myriad MBR-living bacteria [7,8,9]. Thus, the prevalent bacterial communication in MBRs is believed to be Gram-negative QS which is ensured through AHLs as autoinducers.…”
Quorum Quenching (QQ) has been developed over the last few years to overcome practical issues related to membrane biofouling, which is currently the major difficulty thwarting the extensive development of membrane bioreactors (MBRs). QQ is the disruption of Quorum Sensing (QS), cell-to-cell communication enabling the bacteria to harmonize their behavior. The production of biofilm, which is recognized as a major part of the biocake formed on a membrane surface, and which leads to biofouling, has been found to be one of the bacterial behaviors controlled by QS. Since the enzymatic disruption of QS was reported to be efficient as a membrane biofouling mitigation technique in MBRs, the application of QQ to lab-scale MBRs has been the subject of much research using different approaches under different operating conditions. This paper gives an overview of the effectiveness of QQ in mitigating membrane biofouling in MBRs. It is based on the results of previous studies, using two microbial strains, Rhodococcus sp. BH4 and Pseudomonas sp. 1A1. The effect of bacterial QQ on the physical phenomena of the MBR process is analyzed, adopting an original multi-scale approach. Finally, the potential influence of the MBR operating conditions on QQ effectiveness is discussed.
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