2014 - Strategic Project

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Organizational Unit

Publications

Integrated liquid chromatography method in enantioselective studies: biodegradation of ofloxacin by an activated sludge consortium

Publication . Maia, Alexandra S.; Castro, Paula M. L.; Tiritan, M. E.

tOfloxacin is a chiral fluoroquinolone commercialized as racemate and as its enantiomerically pure formlevofloxacin. This work presents an integrated liquid chromatography (LC) method with fluorescencedetection (FD) and exact mass spectrometry (EMS) developed to assess the enantiomeric biodegradationof ofloxacin and levofloxacin in laboratory-scale microcosms. The optimized enantioseparation condi-tions were achieved using a macrocyclic antibiotic ristocetin A-bonded CSP (150 × 2.1 mm i.d.; particlesize 5 m) under reversed-phase elution mode. The method was validated using a mineral salts mediumas matrix and presented selectivity and linearity over a concentration range from 5 g L−1(quantificationlimit) to 350 g L−1for each enantiomer. The method was successfully applied to evaluate biodegrada-tion of ofloxacin enantiomers at 250 g L−1by an activated sludge inoculum. Ofloxacin (racemic mixture)and (S)-enantiomer (levofloxacin) were degraded up to 58 and 52%, respectively. An additional degrad-able carbon source, acetate, enhanced biodegradation up to 23%. (S)-enantiomer presented the highestextent of degradation (66.8%) when ofloxacin was supplied along with acetate. Results indicated slightlyhigher biodegradation extents for the (S)-enantiomer when supplementation was done with ofloxacin.Degradation occurred faster in the first 3 days and proceeded slowly until the end of the assays. Thechromatographic results from LC-FD suggested the formation of the (R)-enantiomer during levofloxacinbiodegradation which was confirmed by LC–MS with a LTQ Orbitrap XL.

2016Journal article

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Removal of fluoxetine and its effects in the performance of an aerobic granular sludge sequential batch reactor

Publication . Moreira, Irina S.; Amorim, Catarina L.; Ribeiro, Ana R.; Mesquita, Raquel B. R.; Rangel, António O.S.S.; Loosdrecht, Mark C.M. van; Tiritan, Maria E.; Castro, Paula M. L.

Fluoxetine (FLX) is a chiral fluorinated pharmaceutical mainly indicated for treatment of depression and is one of the most distributed drugs. There is a clear evidence of environmental contamination with this drug. Aerobic granular sludge sequencing batch reactors constitute a promising technology for wastewater treatment; however the removal of carbon and nutrients can be affected by micropollutants. In this study, the fate and effect of FLX on reactor performance and on microbial population were investigated. FLX adsorption/desorption to the aerobic granules was observed. FLX shock loads (<= 4 mu M) did not show a significant effect on the COD removal. Ammonium removal efficiency decreased in the beginning of first shock load, but after 20 days, ammonia oxidizing bacteria became adapted. The nitrite concentration in the effluent was practically null indicating that nitrite oxidizing bacteria was not inhibited, whereas, nitrate was accumulated in the effluent, indicating that denitrification was affected. Phosphate removal was affected at the beginning showing a gradual adaptation, and the effluent concentration was <0.04 mM after 70 days. A shift in microbial community occurred probably due to FIX exposure, which induced adaptation/restructuration of the microbial population. This contributed to the robustness of the reactor, which was able to adapt to the FLX load.

2015Journal article

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Remoção de fluoroquinolonas do ambiente: biossorção a lamas ativadas e a grânulos aeróbios

Publication . Ferreira, Vanessa R. A.; Amorim, Catarina L.; Cravo, Sara M.; Tiritan, Maria E.; Castro, Paula M. L.; Afonso, Carlos M. M.

Diversas matrizes ambientais, particularmente águas residuais, têm revelado a presença de antibióticos. Embora presentes em níveis vestigiais (ng.L-1 a µg.L-1,), estes compostos são pseudo-persistentes e, naquelas concentrações, podem também promover resistências nas populações bacterianas [1]. Estudos recentes de remoção de antibióticos com lamas ativadas (AS) e grânulos aeróbios (AGS) mostram a biossorção como processo dominante e eficaz na remoção destes micropoluentes [2,3]. O presente trabalho explorou a biossorção de três fluoroquinolonas (FQ) - ofloxacina (OFL), norfloxacina (NOR) e ciprofloxacina (CPF) - a AS e AGS. Com vista a uma melhor compreensão dos fenómenos que ocorrem durante o processo, foram estudados diversos parâmetros que condicionam a biossorção. As AS demonstraram melhor desempenho na remoção da OFL, NOR e CPF relativamente aos AGS. No entanto, nas concentrações estudadas, não foi possível promover a remoção total dos fármacos. A capacidade mais elevada de biossorção das AS foi atribuída à carga negativa da superfície da biossorção, representada por um potencial zeta de -25,65 mV, a pH 7. A OFL foi a FQ menos removida, tanto pelas AS como pelos AGS, porque a OFL a pH 7 está principalmente presente na forma aniónica, com uma pequena percentagem, na forma zwiteriónica. Em AGS verifica-se um aumento da biossorção da OFL, NOR e CPF em pH ácido (pH 4) e maior dessorção em pH alcalino (pH 8 a 9). Observou-se também que ocorre a destruição da estrutura granular dos AGS quando o pH do meio é igual ou inferior a 3. Os resultados obtidos neste estudo contribuem para uma utilização mais eficaz de AS e AGS na remoção de antibióticos fluoroquinolonas do ambiente.

2014-11Conference object

Open access