186,282 research outputs found
Light-induced changes in photosynthesis and structure of cyanobacteria cultured biofilms from an Italian wastewater treatment plant
No full textThe photosynthetic and light acclimation capability of phototrophic biofilms collected seasonally from the wastewater treatment plant (WWTP) of Fiumicino Airport (Rome, Italy) was tested in culture at different irradiance conditions. Photosynthesis versus Irradiance (P/I) curves were recorded on 15, 30 and 45 day aged communities and chlorophylls, carotenoids and phycobiliproteins quantified. Light microscopy observations were performed to evaluate inoculum species composition and taxonomic shifts over time in cultured biofilms. Phototrophs acclimated to different irradiances by varying the photosynthetic efficiency, maximum photosynthetic rate and pigment content. Community age and biomass variation also affected photosynthesis-light response. Marked shifts towards the prevalence of cyanobacteria were observed in summer and autumn biofilms kept at the highest experimental irradiances. Data indicated high productivity and acclimation potential of cultured phototrophic biofilms in view of their application for bioremediation technologies
Annual photosynthetic response of phototrophic biofilms from an Italian wastewater treatment plant.
No full textMicrobial amino acid yield from in vitro incubation of cellulose or starch with rumen fluid
No full textTwo model substrates, cellulose (particle size 20 mu m) and powdered maize starch, were incubated in vitro in glass syringes with rumen fluid and buffer. The fermentation was monitored after 1 h and every 3 h, up to 24 h of incubation. At the end of each incubation period gas yield was read and the contents of three syringes were removed, separated and analysed. Bacterial dry matter was calculated from total amino acid yield, assuming that this represented 42% of bacterial cells, and substrate degradability was calculated as the difference between residual dry matter and estimated bacterial dry matter at the end of each incubation period. The results obtained for pH, ammonia nitrogen and gas production indicated that the fermentation of cellulose was active from 9 to 21 h of incubation For starch, the active period of fermentation was considered to occur between 3 and 15 h. The amino acid production was significantly different between substrate and times of incubation (P < 0.001); moreover the interaction of the main effects was also very high (P < 0.001). At the end of the selected incubation periods times (21 h for cellulose and 15 h for starch) the quantity of amino acid yielded from the bacteria growing in cellulose was much lower than that obtained from starch (59.4 vs. 89.8 mg AA g(-1) substrate incubated). The amount of lysine and methionine produced during the fermentation of cellulose and starch varied between substrate and time of incubation. The in vitro estimated degradability differed significantly for substrate, time of incubation and their interaction; at the end of the restricted period of incubation considered, the degradability reached a value of 52.7 and 91.8% for cellulose and starch, respectively. The efficiency of bacterial growth (mg AA nitrogen g(-1) substrate degraded) was numerically, but not significantly higher for cellulose than starch (19.3 vs. 15.8 mg AA nitrogen g(-1) respectively) and at the beginning of incubation for both the substrates. (C) 1997 Elsevier Science B.V
Modelling the photosynthesis and the nutrient status of aquatic phototrophic biofilms
No full textI biofilm fototrofi sono comunità di microorganismi fototrofi ed eterotrofi che crescono adesi a ogni superficie sommersa degli impianti di depurazione delle acque grazie all’energia solare, che sostiene il processo fotosintetico, e al flusso costante di acqua, che consente un apporto continuo di nutrienti inorganici. Finora, l’ecofisiologia dei biofilm fototrofi di ambiente acquatico è stata scarsamente caratterizzata in coltura. Lo scopo di questa tesi è stato quello di valutare le caratteristiche fotosintetiche, la fotoacclimatazione e la capacità di rimozione dei nutrienti dalle acque di biofilm fotosintetici di impianti di depurazione in condizioni controllate di crescita. Questo studio è parte del progetto europeo PHOBIA che ha lo scopo di sviluppare un modello concettuale unitario per i biofilms fototrofi in ambiente acquatico.
I biofilm venivano campionati dalle pareti della vasca di sedimentazione dell’impianto di depurazione delle acque reflue dell’aeroporto “Leonardo da Vinci”, Fiumicino (Roma, Italia) e messi in coltura in un prototipo di incubatore a diverse condizioni di irradianza, temperatura e velocità di flusso del terreno di coltura. L’effettiva resa quantica del fotosistema II (PSII) e curve di fotosintesi Electron Transport Rate versus Irradiance (ETR/I) erano registrate allo stadio iniziale, attivo e maturo di sviluppo dei biofilm mediante un fluorimetro PAM (Pulse Amplitude Modulated), e le clorofille, i carotenoidi e le ficobiliproteine quantificate per determinare la capacità fotosintetica e di fotoacclimatazione della comunità, e la variazione di biomassa nel tempo. Metodi spettrofotometrici erano utilizzati per quantificare l’azoto e il fosforo totali nei biofilm, con lo scopo di valutare la capacità di rimozione dei due nutrienti. Inoltre, dei campioni erano fissati per la microscopia elettronica a trasmissione e osservati per visualizzare le riserve di azoto e fosforo intracellulari.
I biofim crescevano in coltura raggiungendo un’elevata biomassa nelle varie condizioni di crescita. L’utilizzo del fluorimetro PAM consentiva di valutare rapidamente e in maniera non invasiva la capacità fotosintetica dei biofilm. La resa quantica del PSII era significativamente influenzata dalle condizioni sperimentali, con valori più elevati a irradianza crescente e a valori bassi di temperatura e flusso. I risultati delle curve ETR/I mostravano la capacità di acclimatazione dei fototrofi alle diverse condizioni di irradianza, come confermato ulteriormente dalla variazione del contenuto dei pigmenti fotosintetici. I dati spettrofotometrici rivelavano alte concentrazioni di azoto e fosforo nei biofilm a indicare che i due nutrienti venivano rapidamente sottratti dal mezzo di coltura e accumulati dai biofilm durante la crescita. Inoltre, condizioni di bassa temperatura e flusso influenzavano positivamente l’accumulo dei nutrienti. I cianobatteri e le microalghe erano attivamente coinvolti nella rimozione di azoto e fosforo come evidenziato a livello ultrastrutturale dalla presenza di granuli di cianoficina e accumuli di polifosfato, rispettivamente.
La comprensione dei processi di acclimatazione e della dinamica di rimozione dei nutrienti nei biofilm fototrofi di impianti di depurazione è di primaria importanza per lo sviluppo di un trattamento terziario alternativo e ecologicamente sicuro basato sull’impiego di comunità autoctone. In quest’ottica, il passo successivo è rappresentato dall’isolamento e coltura di specie che accoppiano elevata produttività e efficienza di rimozione dei nutrienti per la creazione in laboratorio di inoculi di biofilm da utilizzare nel processo di depurazione.Phototrophic biofilms are an ensemble of photo- and heterotrophic microorganisms which grow attached to every submerged surface of wastewater treatment plants (WWTPs) thanks to the solar energy, which support the photosynthetic processes, and to the constant water flow, which provides a continuous load of inorganic nutrients. Hitherto, the ecophysiology of aquatic phototrophic biofilms from WWTPs has been poorly characterised in culture. The aim of this thesis was to assess the photosynthetic characteristics, photoacclimation and nutrient removal ability of phototrohic biofilms from an Italian WWTP under controlled conditions. This study was part of the PHOBIA EU-Project aimed at developing a unifying model of structure and functioning of aquatic phototrotrophic biofilms.
Biofilms were collected from the walls of the sedimentation tank (ST) of the Leonardo da Vinci Airport WWTP, Fiumicino (Rome, Italy) and cultured in an incubator prototype at different irradiance, temperature and flow regime. Effective quantum yield of photosystem II (ΔF/Fm') and Electron Transport Rate versus Irradiance (ETR/I) curves were recorded at initial, active and mature stages of biofilm development by means of a Pulse Amplitude Modulated (PAM) fluorometer, and the chlorophylls, carotenoids and phycobiliproteins quantified to determine the community photosynthetic and photoacclimation ability, and phototrophic biomass variation over time. In order to assess the nutrient removal ability, spectrophotometric methods were used to quantify the total nitrogen (N) and phosphorus (P) content in cultured biofilms. Samples were also fixed for transmission electron microscopy (TEM) and observed to visualise intracellular N and P reserves.
Biofilms were able to grow in culture attaining high biomass in the different conditions tested. PAM-fluorescence technique provided a rapid and non-invasive assessment of the photosynthetic performance. ΔF/Fm' was significantly affected by the different conditions tested, with higher values obtained at increasing growth irradiance, low temperature and low flow. Data obtained by ETR/I curves recordings demonstrated the acclimation ability of phototrophs to varying irradiance as further confirmed by the variation of photosynthetic pigments. Spectrophotometric data revealed high N and P concentrations in the biofilms indicating that the two nutrients were rapidly removed from the medium and stored by the biofilms during growth. In addition, low temperature and flow positively influenced P retention in the biofilms. Cyanobacteria and microalgae were actively involved in N and P removal and accumulation as evidenced at ultrastructural level by the occurrence of cyanophycin granules and polyphosphate bodies, respectively.
Understanding acclimation processes and nutrient removal dynamics in WWTP phototrophic biofilms is of major importance to the development of alternative and environmentally sound tertiary water treatment exploiting autochthonous communities. On this basis, the following step is represented by the isolation and culturing of species that couple high productivity and nutrient removal efficiency for the laboratory creation of biofilm inocula to be used in the depuration process
DASH II: Inter-rater reliability and factor structure in people with severe and profound ID
No full textCaratterizzazione enologica e molecolare di ceppi di Oenococcus oeni resistenti a basse temperature e ad alte dosi di anidride solforosa
No full textUna selezione di batteri malolattici da vini trentini commercializzata in tutto il mondo
No full textPhototrophic biofilms in wastewaters: application of transmission electron microscopy techniques to bioremediation studies.
No full textDASH II: Intrer-rater reliability and factor structure in people with severe and profound ID
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