Application of a yeast-based assay protocol developed to monitor total oestrogenic activity induced by 17&#233-oestradiol in activated sludge supernatants from batch experiments

Batch experiments were carried out with activated sludge from laboratory reactors and a full-scale treatment plant spiked with 17β-oestradiol (E2). An oestrogen-sensitive yeast-based assay protocol, described in detail in a related publication, was used to measure reduction of E2-induced total oestrogenic activity from the sludge supernatant over a 15 d period after which the sludge was re-spiked to check for possible enhancement of reduction by pre-exposed sludge during an additional 15 d period. The reduction was generally improved by increasing sludge solids concentrations and by continuous mixing. For a 100 ngE2/ℓ spike there was >40% reduction of oestrogenic activity within 15 d, which improved to >70% by pre-exposing the sludge. The oestrogenic activity produced by a dose of 100 μgE2/ℓ was readily removed by most sludges within 15 d. However, re-spiking the activated sludge with the same E2 concentration caused some sludges to lose reduction capacity. Water SA Vol.32 (3) 2006: pp.355-36

Simultaneous removal of phosphorus and nitrogen from sewage using a novel combo system of fluidized bed reactor-membrane bioreactor (FBR-MBR)

A FBR-MBR combo system was designed as a novel approach for simultaneous phosphorus and nitrogen removal from sewage. The combo system was evaluated more than 7months under variable pH (7.5-9.5), hydraulic retention times (HRT=2-10h), intermittent aeration cycles (IAC) (on/off=60/60-15/45min) and sludge retention times (SRT=10-60d). Prior recovery of phosphorus as struvite in the FBR enhanced nitrogen and COD removal efficiency in MBR. Under optimum operating conditions (pH=9, HRT=6h and IAC=45/15min), PO43--P, NH4+-N and COD removal efficiencies were 92.6±4.2, 98.7±1.2 and 99.3±0.5%, respectively. Stable mixed liquor suspended solid concentration (3.0-5.0g/L); enhanced nitrification-denitrification activity (78-92%) and reduced transmembrane pressure were also achieved. Compared to soluble microbial products, extracellular polymeric substances (EPS) showed strong correlation with fast membrane fouling. Among EPS components, carbohydrate rather than protein was associated with membrane fouling. Except HRT, all parameters considered (pH, IAC, SRT) showed a significant effect on removal efficiency. © 2013 Elsevier Ltd

Effect of intermittent aeration cycle on nutrient removal and microbial community in a fluidized bed reactor-membrane bioreactor combo system

Effect of intermittent aeration cycle (IAC=15/45-60/60min) on nutrient removal and microbial community structure was investigated using a novel fluidized bed reactor-membrane bioreactor (FBR-MBR) combo system. FBR alone was found more efficient for removing PO4-P (>85%) than NH4-N (98%). Efficient nitrification, stable mixed liquor suspended solid and reduced transmembrane pressure was also achieved. Quantitative real-time polymerase chain reaction results of total bacteria 16S rRNA gene copies per mL of mixed-liquor varied from (2.48±0.42)×109 initial to (2.74±0.10)×108, (6.27±0.16)×109 and (9.17±1.78)×109 for 15/45, 45/15 and 60/60min of IACs, respectively. The results of clone library analysis revealed that Proteobacteria (59%), Firmicutes (12%) and Bacteroidetes (11%) were the dominant bacterial group in all samples. Overall, the combo system performs optimum nutrient removal and host stable microbial communities at 45/15min of IAC. © 2014 Elsevier Ltd

A mathematical model of quorum sensing regulated EPS production in biofilm communities

<p>Abstract</p> <p>Background</p> <p>Biofilms are microbial communities encased in a layer of extracellular polymeric substances (EPS). The EPS matrix provides several functional purposes for the biofilm, such as protecting bacteria from environmental stresses, and providing mechanical stability. Quorum sensing is a cell-cell communication mechanism used by several bacterial taxa to coordinate gene expression and behaviour in groups, based on population densities.</p> <p>Model</p> <p>We mathematically model quorum sensing and EPS production in a growing biofilm under various environmental conditions, to study how a developing biofilm impacts quorum sensing, and conversely, how a biofilm is affected by quorum sensing-regulated EPS production. We investigate circumstances when using quorum-sensing regulated EPS production is a beneficial strategy for biofilm cells.</p> <p>Results</p> <p>We find that biofilms that use quorum sensing to induce increased EPS production do not obtain the high cell populations of low-EPS producers, but can rapidly increase their volume to parallel high-EPS producers. Quorum sensing-induced EPS production allows a biofilm to switch behaviours, from a colonization mode (with an optimized growth rate), to a protection mode.</p> <p>Conclusions</p> <p>A biofilm will benefit from using quorum sensing-induced EPS production if bacteria cells have the objective of acquiring a thick, protective layer of EPS, or if they wish to clog their environment with biomass as a means of securing nutrient supply and outcompeting other colonies in the channel, of their own or a different species.</p

Shaping the growth behaviour of biofilms initiated from bacterial aggregates

Bacterial biofilms are usually assumed to originate from individual cells deposited on a surface. However, many biofilm-forming bacteria tend to aggregate in the planktonic phase so that it is possible that many natural and infectious biofilms originate wholly or partially from pre-formed cell aggregates. Here, we use agent-based computer simulations to investigate the role of pre-formed aggregates in biofilm development. Focusing on the initial shape the aggregate forms on the surface, we find that the degree of spreading of an aggregate on a surface can play an important role in determining its eventual fate during biofilm development. Specifically, initially spread aggregates perform better when competition with surrounding unaggregated bacterial cells is low, while initially rounded aggregates perform better when competition with surrounding unaggregated cells is high. These contrasting outcomes are governed by a trade-off between aggregate surface area and height. Our results provide new insight into biofilm formation and development, and reveal new factors that may be at play in the social evolution of biofilm communities

Application of a yeast-based assay protocol developed to monitor total oestrogenic activity induced by 17β-oestradiol in activated sludge supernatants from batch experiments

This is a research paper on Application of a yeast-based assay protocol developed to monitor total oestrogenic activity induced by 17β-oestradiol in activated sludge supernatants from batch experimentsBatch experiments were carried out with activated sludge from laboratory reactors and a full-scale treatment plant spiked with 17β-oestradiol (E2). An oestrogen-sensitive yeast-based assay protocol, described in detail in a related publication, was used to measure reduction of E2-induced total oestrogenic activity from the sludge supernatant over a 15 d period after which the sludge was re-spiked to check for possible enhancement of reduction by pre-exposed sludge during an additional 15 d period. The reduction was generally improved by increasing sludge solids concentrations and by continuous mixing. For a 100 ngE2/ℓ spike there was >40% reduction of oestrogenic activity within 15 d, which improved to >70% by pre-exposing the sludge. The oestrogenic activity produced by a dose of 100 μgE2/ℓ was readily removed by most sludges within 15 d. How¬ever, re-spiking the activated sludge with the same E2 concentration caused some sludges to lose reduction capacity

Developing a yeast-based assay protocol to monitor total oestrogenic activity induced by 17β-oestradiol in activated sludge supernatants from batch experiments

This is a research paper on developing a yeast-based assay protocol to monitor total oestrogenic activity induced by 17β-oestradiol in activated sludge supernatants from batch experimentsA yeast-based assay protocol developed for detecting oestrogenic activity in activated sludge (AS) supernatant is described. The protocol used Saccharomyces cerevisiae construct RMY/ER-ERE with human oestrogen receptor (ERα) and lacZ reporter genes, and was developed by modifying existing assays for use with AS samples from batch experiments. The method was able to detect total oestrogenic activity (without prior extraction) in supernatants of AS spiked with 17β-oestra¬diol (E2) with a detection limit of 0.03 ngE2-equivalent/ℓ and an overall quantification limit of 100 ngE2-equivalent/ℓ. Mean E2-induced oestrogenic activity recoveries of >56% were obtained from the spiked samples

Developing a yeast-based assay protocol to monitor total oestrogenic activity induced by 17&#223-oestradiol in activated sludge supernatants from batch experiments

A yeast-based assay protocol developed for detecting oestrogenic activity in activated sludge (AS) supernatant is described. The protocol used Saccharomyces cerevisiae construct RMY/ER-ERE with human oestrogen receptor (ER&#945;) and lacZ reporter genes, and was developed by modifying existing assays for use with AS samples from batch experiments. The method was able to detect total oestrogenic activity (without prior extraction) in supernatants of AS spiked with 17&#946;-oestradiol (E2) with a detection limit of 0.03 ngE2-equivalent/&#8467; and an overall quantification limit of 100 ngE2-equivalent/&#8467;. Mean E2-induced oestrogenic activity recoveries of >56% were obtained from the spiked samples. Water SA Vol.32 (3) 2006: pp.345-35