Interdisciplinary Centre of Marine and Environmental Research

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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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Fluoroquinolones biosorption onto microbial biomass: activated sludge and aerobic granular sludge

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

Fluoroquinolones (FQs) have been reported in trace amounts in different environmental matrices. The biosorption of three most prescribed FQs, ofloxacin (OFL), norfloxacin (NOR) and ciprofloxacin (CPF) by activated sludge (AS) and aerobic granular sludge (AGS) was investigated. Biosorption assays were conducted with FQs concentrations within the range of 100e700 ng mL 1, to mimic environmental conditions. At neutral pH and at the end of 48 h, AS showed higher biosorption capacity than AGS. For AS, a maximum biosorption of 1.50 ± 0.03, 3.24 ± 0.05 and 3.39 ± 0.06 mg gTSS 1 was observed for OFL, NOR and CPF respectively, whereas for AGS the maximum amount of FQs biosorbed was 1.18 ± 0.03, 2.73 ± 0.02 and 2.94 ± 0.03 mg gTSS 1. Langmuir isotherm was more applicable for describing FQs biosorption equilibrium by AS while for AGS, the Freundlich isotherm was more adequate. Given the AGS technology innovative character, the effect of change of pH on the biosorbed FQs was evaluated. FQs could be desorbed from AGS at pH 3, pH 8 and pH 9 but at pH 4 the biosorption process was promoted. This study allows a better understanding of the FQs biosorption processes. Moreover, the data from biosorption/desorption from AGS may be useful for management and operation of AGS bioreactors

2016Journal article

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Evaluation of the impact of fertilizers on soil and soil leachates – chemical composition and microbial community assemblage