| Title | Investigating the influences of quorum quenching and nutrient conditions on activated sludge flocs at a short-time scale |
| Abstract | Quorum sensing signals regulate various functions within activated sludge processes such as formation
of microbial aggregates. Disturbance of this signaling system, known as quorum quenching (QQ), provides
opportunities for eliminating some problems related to biological wastewater treatment (e.g.,
biofouling and excess sludge production). However, it is poorly understood how and to what extent QQ
systems can affect the microbial aggregation processes and the following floc formation. In particular, an
in-depth structural characterization at the scale of microbial aggregate while considering nutrient
conditions in the reactor is still largely disregarded. Here, we evaluated the QQ effects at the short-term
time scale (i.e., after 4 h for the exogenous period and 19 h for exogenous/endogenous period), by
combining advanced techniques for microbial characterization (flow cytometry, CARD-FISH, and confocal
laser scanning microscopy) and conventional physical-chemical assessments. The results indicated that
by implementing QQ agents (immobilized Acylase I enzyme in porous alginate beads) the abundance of
single cells and suspended microbial aggregates in the supernatant did not show significant changes
during the exogenous period. Conversely, at the end of the exogenous/endogenous period a significant
increase of single prokaryotic cells, small and large microbial aggregates favored the growth of grazers,
including free-living nanoflagellates and ciliates. Flocs became looser and thinner than those in the
control reactor, thus affecting the sludge settling behavior. Inability of microbial community in degradation
of soluble protein during the endogenous period confirmed that the QQ agents are likely to inhibit
the secretion of protease enzyme within microbial communities of activated sludge. |
| Source | Chemosphere |
| Keywords | Quorum sensingmicrobial aggregatesEPSProtozoanutrient conditions |
| Journal | Chemosphere |
| Editor | Elsevier, Oxford, Regno Unito |
| Year | 2020 |
| Type | Articolo in rivista |
| Authors | Salehiziri, M., Amalfitano, S., Gallipoli, A., Gianico, A., Amini Rad, H., Braguglia, C.M., Fazi, S. |
| Text | 420315 2020 Quorum sensing microbial aggregates EPS Protozoa nutrient conditions Investigating the influences of quorum quenching and nutrient conditions on activated sludge flocs at a short time scale Salehiziri, M., Amalfitano, S., Gallipoli, A., Gianico, A., Amini Rad, H., Braguglia, C.M., Fazi, S. Babol Noshirvani University of Technology, Babol, Iran Water Research Institute, National Research Council of Italy IRSA CNR , Via Salaria Km 29,300, 00015, Monterotondo, Roma, Italy Quorum sensing signals regulate various functions within activated sludge processes such as formation of microbial aggregates. Disturbance of this signaling system, known as quorum quenching QQ , provides opportunities for eliminating some problems related to biological wastewater treatment e.g., biofouling and excess sludge production . However, it is poorly understood how and to what extent QQ systems can affect the microbial aggregation processes and the following floc formation. In particular, an in depth structural characterization at the scale of microbial aggregate while considering nutrient conditions in the reactor is still largely disregarded. Here, we evaluated the QQ effects at the short term time scale i.e., after 4 h for the exogenous period and 19 h for exogenous/endogenous period , by combining advanced techniques for microbial characterization flow cytometry, CARD FISH, and confocal laser scanning microscopy and conventional physical chemical assessments. The results indicated that by implementing QQ agents immobilized Acylase I enzyme in porous alginate beads the abundance of single cells and suspended microbial aggregates in the supernatant did not show significant changes during the exogenous period. Conversely, at the end of the exogenous/endogenous period a significant increase of single prokaryotic cells, small and large microbial aggregates favored the growth of grazers, including free living nanoflagellates and ciliates. Flocs became looser and thinner than those in the control reactor, thus affecting the sludge settling behavior. Inability of microbial community in degradation of soluble protein during the endogenous period confirmed that the QQ agents are likely to inhibit the secretion of protease enzyme within microbial communities of activated sludge. Published version Articolo in rivista Elsevier 0045 6535 Chemosphere Chemosphere Chemosphere Chemosphere. Chemosphere. Environmental chemistry, Chemosphere. Persistent organic pollutants and dioxins, Chemosphere. Environmental toxicology and risk assessment, Chemosphere. Science for Environmental toxicology, stefano.fazi FAZI STEFANO camillamaria.braguglia BRAGUGLIA CAMILLA MARIA stefano.amalfitano AMALFITANO STEFANO andrea.gianico GIANICO ANDREA agata.gallipoli GALLIPOLI AGATA |
