Degradation of fluoroquinolone antibiotics and identification of metabolites/transformation products by liquid chromatography–tandem mass spectrometry

Optimization and validation of multiresidual extraction methods for pharmaceuticals in Soil, Lettuce, and Earthworms

The presence of human and veterinary pharmaceuticals (PhACs) in the environment poses potential risks. To comprehensively assess these risks, robust multiresidual analytical methods are essential for determining a broad spectrum of PhAC classes in various environmental compartments (soil, plants, and soil organisms). This study optimized extraction methods for analyzing over 40 PhACs from various matrices, including soil, lettuce, and earthworms. A four-step ultrasonic extraction method with varying extraction conditions and subsequent solid phase extraction was developed for soil samples. QuEChERS methods were optimized for extracting PhACs from lettuce and earthworm samples, addressing a literature gap in these less-studied matrices. The quantification of PhACs in soil, lettuce, and earthworm extracts was performed using a single LC-MS/MS method. Following thorough method validation, earthworms and lettuce were exposed to a mixture of 27 pharmaceuticals in a soil environment. The method validation results demonstrated the robustness of these methods for a broad spectrum of PhACs. Specifically, 29 out of 42 PhACs were extracted with an average efficiency > 50% and RSD < 30% from the soil; 40 out of 42 PhACs exhibited average efficiency > 50% and %RSD < 30% from the earthworms, while 39 out of 42 PhACs showed average efficiency > 50% and RSD < 30% from the lettuce. Exposure experiments confirmed the viability of these methods for quantifying a diverse range of PhACs in different environmental compartments. This study presents three thoroughly validated methods for determining more than 40 PhACs in diverse matrices, enabling a comprehensive assessment of PhAC dissemination in the environment.

Defect-mediated time-efficient photocatalytic degradation of methylene blue and ciprofloxacin using tungsten-incorporated ternary perovskite BaSnO3 nanoparticles

Photocatalytic water purification has been extensively explored for its economic, eco-friendly, and sustainable aspects. In this study, tungsten (W) incorporated BaSn1-xWxO3 (x = 0 to 0.05) nanoparticles synthesized by facile hydrogen peroxide precipitation route has been demonstrated for photocatalytic degradation of methylene blue (MB) dye and ciprofloxacin (CIP) antibiotic. The structural analysis indicates the presence of hybrid composite-like nanostructures with reduced crystallinity. Optical studies reveal blueshift in bandgap and decrease in oxygen vacancy defects upon W-incorporation. Pure BaSnO3 shows overall enhanced photocatalytic activity towards MB (90.22%) and CIP (78.12%) after 240 min of white LED light and sunlight irradiation respectively. The 2 % W-incorporated BaSnO3 shows superior photocatalytic degradation of MB (26.89%) and CIP (45.14%) within first 30 min of irradiation confirming the presence of W to be beneficial in the process. The free radical study revealed the dominant role of reactive hole (h+) and oxygen radical (O2•-) species during photodegradation and their intermediates are investigated to elucidate the degradation mechanism of MB within 30 min of irradiation. This study is promising towards developing defect mediated and time-efficient photocatalysts for environmental remediation.

An investigation on removal of ciprofloxacin and norfloxacin by phycoremediation with an emphasis on acute toxicity and biochemical composition

Ciprofloxacin (CIP) and norfloxacin (NOR) belong to the class of emerging contaminants that are frequently detected in the aquatic environment as a binary mixture, responsible for the development of antibiotic-resistant genes and antibiotic-resistant bacteria. This study aims to investigate five different algal species Chlorella vulgaris (Cv), Chlorella pyrenoidosa (Cp), Scenedesmus obliquus (So), Tetradesmus sp (T) and Monoraphidium sp (M) for their tolerance and removal of binary mixture. The effects on biochemical composition in the algal species concerning the binary mixture and its removal efficiency are first reported in this study. The acute toxicity (96 h EC50) values are in the order of So > Cp > T > M > Cv, Chlorella vulgaris is the most sensitive algal species with 17.73 ± 0.24 mg/L and Scenedesmus obliquus is the least sensitive algal species with 39.19 ± 0.79 mg/L. The removal efficiency of the binary mixture was found to be in the order of So > Cp > T > M > Cv, Scenedesmus obliquus removed CIP (52.4%) and NOR (87.5%) with biodegradation as the major contributing removal mechanism. Furthermore, less toxic biotransformed products were detected in Scenedesmus obliquus and the biochemical characterization revealed that the growth-stimulating effect is higher with lipid (35%), carbohydrate (18%), and protein (33%) providing an advantage in the production of valuable biomass.

Construction of graphene quantum dots ratiometric fluorescent probe by intermolecular electron transfer effect for intelligent and real-time visual detection of ofloxacin and its L-isomer in daily drink

The design of intelligent and real-time sensing devices is significant in the medical drug monitoring field, but it is still highly challenging. Here, ratiometric fluorescent detections of ofloxacin (OFL) and its L-isomer levofloxacin (LEV) constructed from tri-doped graphene quantum dots (T-GQDs) are reported, and the detection limits reach as low as 46/67 nM toward OFL/LEV due to the intermolecular electron transfer (intermolecular ET) effect. After adding OFL/LEV, the generation of electrostatic bond provides a channel for the intermolecular ET from the edge of T-GQDs to OFL/LEV, resulting in the fluorescence quenching at 414 nm and the fluorescence promoting at 498 nm. Furthermore, a smartphone can be used for the visual and quantitative detection of OFL and LEV by identifying the RGB values of test paper and drink samples. This work not only reveals the physics mechanism of ratiometric detection, but also develops a convenient smartphone diagnostic for OFL and LEV.

Extracellular polymeric substances-antibiotics interaction in activated sludge: A review

Antibiotics, the most frequently prescribed drugs, have been widely applied to prevent or cure human and veterinary diseases and have undoubtedly led to massive releases into sewer networks and wastewater treatment systems, a hotspot where the occurrence and transformation of antibiotic resistance take place. Extracellular polymeric substances (EPS), biopolymers secreted via microbial activity, play an important role in cell adhesion, nutrient retention, and toxicity resistance. However, the potential roles of sludge EPS related to the resistance and removal of antibiotics are still unclear. This work summarizes the composition and physicochemical characteristics of state-of-the-art microbial EPS, highlights the critical role of EPS in antibiotics removal, evaluates their defense performances under different antibiotics exposures, and analyzes the typical factors that could affect the sorption and biotransformation behavior of antibiotics. Next, interactions between microbial EPS and antibiotic resistance genes are analyzed. Future perspectives, especially the engineering application of microbial EPS for antibiotics toxicity detection and defense, are also emphatically stressed.

Fluoroquinolone antibiotics: Occurrence, mode of action, resistance, environmental detection, and remediation - A comprehensive review

Antibiotics play an essential role in the medical healthcare world, but their widespread usage and high prevalence have posed negative environmental consequences. During the past few decades, various antibiotic drugs have been detected in aquatic and terrestrial ecosystems. Among them, the Fluoroquinolones (FQ) group is ubiquitous in the environment and has emerged as a major environmental pollutant. FQs are very significant, broad-spectrum antibiotics used in treating various pathogenic diseases of humans and animals. The most known and used FQs are ciprofloxacin, norfloxacin, ofloxacin, levofloxacin, enrofloxacin, danofloxacin, and moxifloxacin. After human and animal administration, about 70% of these drugs are excreted out in unaltered form into the environment. Besides, wastewater discharge from pharmaceutical industries, hospitals, and agriculture runoff is the major contributor to the accumulation of FQs into the ecosystem. Their long-term presence in the environment creates selection pressure on microorganisms and contributes to the emergence of multi-drug-resistant bacteria. In addition to the resistance, these antibiotics also impose ecotoxicological effects on various animals and plant species. The presence of the fluorine atom in Fluoroquinolones makes them highly electronegative, strong, recalcitrant, and less compatible with microbial degradation. Many biological and chemical processes have been invented and successfully implemented during the past few decades for the elimination of these pollutants from the environment. This review provides a detailed overview of the classification, occurrence, distribution, and ecotoxicological effects of Fluoroquinolones. Their modes of action, resistance mechanism, detection and analysis methods, and remediation strategies have also been discussed in detail.

The New Strategy for Studying Drug-Delivery Systems with Prolonged Release: Seven-Day In Vitro Antibacterial Action

The new method of antibacterial-drug-activity investigation in vitro is proposed as a powerful strategy for understanding how carriers affect drug action during long periods (7 days). In this paper, we observed fluoroquinolone moxifloxacin (MF) antibacterial-efficiency in non-covalent complexes, with the sulfobutyl ether derivative of β-cyclodextrin (SCD) and its polymer (SCDpol). We conducted in vitro studies on two Escherichia coli strains that differed in surface morphology. It was found that MF loses its antibacterial action after 3-4 days in liquid media, whereas the inclusion of the drug in SCD led to the increase of MF antibacterial activity by up to 1.4 times within 1-5 days of the experiment. In the case of MF-SCDpol, we observed a 12-fold increase in the MF action, and a tendency to prolonged antibacterial activity. We visualized this phenomenon (the state of bacteria, cell membrane, and surface morphology) during MF and MF-carrier exposure by TEM. SCD and SCDpol did not change the drug's mechanism of action. Particle adsorption on cells was the crucial factor for determining the observed effects. The proteinaceous fimbriae on the bacteria surface gave a 2-fold increase of the drug carrier adsorption, hence the strains with fimbriae are more preferable for the proposed treatment. Furthermore, the approach to visualize the CD polymer adsorption on bacteria via TEM is suggested. We hope that the proposed comprehensive method will be useful for the studies of drug-delivery systems to uncover long-term antibacterial action.

rGO-WO3 Heterostructure: Synthesis, Characterization and Utilization as an Efficient Adsorbent for the Removal of Fluoroquinolone Antibiotic Levofloxacin in an Aqueous Phase

Herein, the heterostructure rGO-WO₃ was hydrothermally synthesized and characterized by HRTEM (high-resolution transmission electron microscopy), FESEM (field emission scanning electron microscopy), XRD (X-ray diffraction), FT-IR (Fourier transform infrared spectroscopy), XPS (X-ray photoelectron microscopy), nitrogen physisorption isotherm, Raman, TGA (thermogravimetric analysis) and zeta potential techniques. The HRTEM and FESEM images of the synthesized nanostructure revealed the successful loading of WO₃ nanorods on the surface of rGO nanosheets. The prepared heterostructure was utilized as an efficient adsorbent for the removal of a third-generation fluoroquinolone antibiotic, i.e., levofloxacin (LVX), from water. The adsorption equilibrium data were appropriately described by a Langmuir isotherm model. The prepared rGO-WO₃ heterostructure exhibited a Langmuir adsorption capacity of 73.05 mg/g. The kinetics of LVX adsorption followed a pseudo-second-order kinetic model. The adsorption of LVX onto the rGO-WO₃ heterostructure was spontaneous and exothermic in nature. Electrostatic interactions were found to have played a significant role in the adsorption of LVX onto the rGO-WO₃ heterostructure. Thus, the prepared rGO-WO₃ heterostructure is a highly promising material for the removal of emerging contaminants from aqueous solution.

Ozone-enhanced TiO2 nanotube arrays for the removal of COVID-19 aided antibiotic ciprofloxacin from water: Process implications and toxicological evaluation

The purpose of this study was to evaluate the performance of synthesized TiO₂ nanotube arrays (NTAs) for the removal of the COVID-19 aided antibiotic ciprofloxacin (CIP) and the textile dye methylene blue (MB) from model wastewater. Synthesis of TiO₂ NTAs showed that anodization potential and calcination temperatures directly influence nanotube formation. The increased anodization potential from 10 to 40 V resulted in the development of larger porous nanotubes with a diameter of 36-170 nm, while the collapse of the tubular structure was registered at the highest applied potential. Furthermore, it was found that the 500 °C calcination temperature was the most prominent for the formation of the most photocatalytically active TiO₂ NTAs, due to the optimal anatase/rutile ratio of 4.60. The degradation of both model compounds was achieved with all synthesized TiO₂ NTAs; however, the most photocatalytically active NTA sample was produced at 30 V and 500 ^°C. Compared to photocatalysis, CIP degradation was greatly enhanced by 5-25 times when ozone was introduced to the photocatalytic cell (rates 0.4-4.2 × 10^-1 min^-1 versus 0.07-0.2 × 10^-1 min^-1). This resulted in the formation of CIP degradation by-products, with different mass-to-charge ratios from [M+H]⁺ 346 to 273 m/z. Even though the CIP degradation pathway is rather complex, three main mechanisms, decarboxylation, hydroxylation reaction, and piperazine ring cleavage, were proposed and explained. Furthermore, treated samples were placed in contact with the crustaceans Daphnia magna. It was found that 100% mortality was achieved when approximately 60% of the remaining TOC was present in the samples, indicating that toxic degradation by-products were formed.

Comparing the efficiency of N-doped TiO2 and commercial TiO2 as photo catalysts for amoxicillin and ciprofloxacin photo-degradation under solar irradiation

Advanced oxidation processes (AOPs) have gained traction as alternative solutions for eliminating pollutants from pharmaceutical wastewater for reuse. In this research, the performance of two photo-catalysts (Commercial TiO₂ and synthesis N-doped TiO₂) were compared in terms of the degradation of amoxicillin and ciprofloxacin from an aqueous solution using a photo-catalytic batch system under solar irradiation. The influence of five operating factors is: pH (5-11), H₂O₂ concentrations (200-600) mg/L, catalyst concentrations (25-100 mg/L), Antibiotic concentration (25-100) mg/L and reaction time (30-120 min), on the oxidation of the listed above pollutants were investigated using the central composite design (CCD) of response surface methodology (RSM). The catalyst of N-doping TiO₂ was synthesized by sol-gel method, using the urea (CH₄N₂O) as a nitrogen source. The resulting material was analyzed using Scanning Electron Microscopy (SEM), X-Ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). Additionally, it can be observed from the analysis of the characteristics of N-doped TiO₂ the homogenous dispersion of nitrogen molecules, small particle sizes, and energy-gap reduction, prompting a 6% increase in antibiotic degradation compared with Com. TiO₂. In the RSM analysis, the ideal conditions were found to be a pH of 5, H₂O₂ conc. of 400 mg/L, catalyst conc. of 50 mg, and antibiotics conc. of 25 mg/L for an antibiotics reduction rate of 89.31% (AMOX/Com. TiO₂/Solar), 90.2 (CFX/Com. TiO₂/Solar), 95.8% (AMOX/N-TiO₂/Solar) and 97.3% (CFX/N-TiO₂/Solar). Experimental results were in good agreement with predictions because the predicted R² matched well with the adjusted R².

Acinetobacter baumannii, Klebsiella pneumoniae and Elizabethkingia miricola isolated from wastewater have biodegradable activity against fluoroquinolone

Ciprofloxacin (CIP) and levofloxacin (LEV), widely used fluoroquinolone antibiotics, are often found in sewage from the sewage treatment plants and marine environment. In this study, CIP and LEV biodegrading bacterial consortia were obtained from industrial wastewater. Microorganisms in these consortia were identified as Acinetobacter baumannii (A. baumannii), Klebsiella pneumoniae (K. pneumoniae) and Elizabethkingia miricola (E. miricola). The impacts of the critical operating parameters on the elimination of CIP and LEV by bacterial consortia have been investigated and optimized to achieve the maximum levels of CIP and LEV biodegradation. Using liquid chromatography with tandem mass spectrometry (LC-MS-MS), possible degradation pathways for CIP and LEV were suggested by analyzing the intermediate degradation products. The role of the enzymes fluoroquinolone-acetylating aminoglycoside (6'-N-acetyltransferase) and cytochrome P450 (CYP450) in the breakdown of fluoroquinolones (FQs) was investigated as well. According to our findings, various biodegradation mechanisms have been suggested, including cleavage of piperazine ring, substitution of F atom, hydroxylation, decarboxylation, and acetylation, as the main biotransformation reactions. This study discovers the ability of non-reported bacterial strains to biodegrade both CIP and LEV as a sole carbon source, providing new insights into the biodegradation of CIP and LEV.

Microbial degradation of antibiotic: future possibility of mitigating antibiotic pollution

Antibiotics are the major pharmaceutical wastes that are being exposed to the environment from the pharmaceutical industries and for the anthropogenic activities. The use of antibiotics for disease prevention and treatment in humans has been surpassed by the amount used in agriculture, particularly on livestock. It is stipulated that the overuse of antibiotics is the single largest reason behind the rise of bacterial anti-microbial resistance (AMR). The development of alternative therapy, like gene therapy, immunotherapy, use of natural products, and various nanoparticles, to control bacterial pathogens might be an alternative of antibiotics for mankind but the remediation of already exposed antibiotics from the lithosphere and hydrosphere needs to be envisioned with priority. The ever-increasing release of antibiotics in the environment makes it one of the major emerging contaminants (ECs). Decomposition of such antibiotic contaminants is a great challenge to get a cleaner environment. There are reports describing the degradation of antibiotics by photolysis, hydrolysis, using cathode and metal salts, or by degradation via microbes. Antimicrobials like sulfonamides are recalcitrant to natural biodegradation, exhibiting high thermal stability. There are recent reports on microbial degradation of a few common antibiotics and their derivatives but their applications in waste management are scanty. It could however be a major concern to the scientists whether to use the antibiotic degradation traits of a microbe for the removal of antibiotic wastes. The complexity of the genetic clusters of a microbe that are responsible for degradation is crucial, as a small genetic cluster might have higher chance of horizontal transfer into sensitive species of the normal microbial flora that in turn triggers the rise of antimicrobial resistance.

Physiological and transcriptomic responses of Chlorella sorokiniana to ciprofloxacin reveal molecular mechanisms for antibiotic removal

Microalgae-based technology is an effective and environmentally friendly method for antibiotics-contaminated wastewater treatment. To assess the tolerance and removal ability of Chlorella sorokiniana to ciprofloxacin (CIP), this study comprehensively revealed the responses of C. sorokiniana to CIP exposure and its degradation processes through physiological and transcriptomic analyses. Although the photosynthetic system was inhibited, the growth of C. sorokiniana was not negatively affected by CIP. Dissolved organic matter was analyzed and indicated that humic-like substances were released to alleviate the stress of CIP. In addition, the maximum removal of CIP was 83.3% under 20 mg L-1 CIP exposure. HPLC-MS/MS and RNA-Seq analyses suggested that CIP could be bioaccumulated and biodegraded by C. sorokiniana through the reactions of hydroxylation, demethylation, ring cleavage, oxidation, dehydrogenation, and decarboxylation with the help of intracellular oxidoreductases, especially cytochrome P450. Collectively, this research shows that C. sorokiniana have a great potential for removing CIP from wastewater.

Study of Oxidation of Ciprofloxacin and Pefloxacin by ACVA: Identification of Degradation Products by Mass Spectrometry and Bioautographic Evaluation of Antibacterial Activity

The new RP-HPLC-DAD method for the determination of ciprofloxacin and pefloxacin, next to their degradation products after the oxidation reaction with 4,4′-azobis(4-cyanopentanoic acid) (ACVA) was developed. The method was validated according to the guidelines of the International Council for Harmonization of Technical Requirements for Pharmaceuticals for Human Use (ICH) and meets the acceptance criteria. The experimental data indicate that the course of the oxidation process depends on the type of fluoroquinolone (FQ), the incubation time and temperature. The performed kinetic evaluation allowed us to state that the oxidation of FQs proceeds according to the second-order kinetics. The degradation products of the FQs were identified using the UHPLC-MS/MS method and their structures were proposed. The results obtained by the TLC-direct bioautography technique allowed us to state that the main ciprofloxacin and pefloxacin oxidation products probably retained antibacterial activity against Escherichia coli.

Detection and remediation of chiral pharmaceuticals from wastewater: A review

Chiral organic pollutants including pharmaceuticals, pesticides, herbicides, flame retardants, and polycyclic musk cause significant risks to both the environment and human health. Chiral pharmaceuticals (CPs) are among the significant class of pseudo-persistent substances that have been observed in the concentration level from nanomolar to micromolar quantities and cause bad impacts on nontargeted species and direct or indirect human health issues due to water and foodborne contamination. The CPs may contain one or more chiral centers in their structural framework and thus enantiomers of CPs often possess different distribution, fate, bioaccumulation potential, and toxicity. The enantioselective chromatographic techniques have been extensively applied to detect drug enantiomers during the last few years. Bioremediation techniques offer unique characteristics above conventional remediation procedures as these could be cost-effective and accomplish total organic pollutant decomposition without causing collateral damage to the site material or native flora and fauna. This review describes the impacts of chiral pharmaceuticals on the environment; detection technologies (particularly liquid chromatography), and important remedial measures for safer disposal of such pollutants.

Norfloxacin and gentamicin degradation catalyzed by manganese porphyrins under mild conditions: the importance of toxicity assessment

The current work assessed the degradation degree and the degradation products derived from norfloxacin (NOR) and gentamicin (GEN) using iodosylbenzene and iodobenzene diacetate, in the presence of manganese porphyrin as catalysts. Better results for NOR degradation (> 80%) were obtained when more hydrophobic porphyrins were employed. β-brominated manganese porphyrins showed a lower GEN degradation (~ 25%) than the non-brominated ones (~ 35%), probably due to their steric hindrance. In any case, complete mineralization was achieved neither for NOR nor for GEN, and the assignment of the generated products, complemented by the study of their toxicity, was an important step performed. From the obtained results, no correlation was found between the number of identified products and the reported toxicity value (r_Spearman,NOR = 0.006; p value = 0.986 and r_Spearman,GEN =  - 0,198; p value = 0.583), which reinforces the idea of synergism and antagonistic phenomena. The higher degradation degree could have led to products of lower steric hindrance and easier penetration into the A. fischeri cells, which subsequently led to an increase in toxicity for these experiments. In most cases, the products presented higher toxicity than the original compound, which raises a concern about their occurrence in environmental matrices.

Treatment technologies to mitigate the harmful effects of recalcitrant fluoroquinolone antibiotics on the environ- ment and human health

Antibiotic proliferation in the environment and their persistent nature is an issue of global concern as they induce antibiotic resistance threatening both human health and the ecosystem. Antibiotics have therefore been categorized as emerging pollutants. Fluoroquinolone (FQs) antibiotics are an emerging class of contaminants that are used extensively in human and veterinary medicine. The recalcitrant nature of fluoroquinolones has led to their presence in wastewater, effluents and water bodies. Even at a low concentration, FQs can stimulate antibacterial resistance. The main sources of FQ contamination include waste from pharmaceutical manufacturing industries, hospitals and households that ultimately reaches the wastewater treatment plants (WWTPs). The conventional WWTPs are unable to completely remove FQs due to their chemical stability. Therefore, the development and implementation of more efficient, economical, convenient treatment and removal technologies are needed to adequately address the issue. This review provides an overview of the technologies available for the removal of fluoroquinolone antibiotics from wastewater including adsorptive removal, advanced oxidation processes, removal using non-carbon based nanomaterials, microbial degradation and enzymatic degradation. Each treatment technology is discussed on its merits and limitations and a comparative view is presented on the choice of an advanced treatment process for future studies and implementation. A discussion on the commercialization potential and eco-friendliness of each technology is also included in the review. The importance of metabolite identification and their residual toxicity determination has been emphasized. The last section of the review provides an overview of the policy interventions and regulatory frameworks that aid in retrofitting antibiotics as a central key focus contaminant and thereby defining the discharge limits for antibiotics and establishing safe manufacturing practices.

Antibiotics: An overview on the environmental occurrence, toxicity, degradation, and removal methods

Antibiotics, as antimicrobial drugs, have been widely applied as human and veterinary medicines. Recently, many antibiotics have been detected in the environments due to their mass production, widespread use, but a lack of adequate treatment processes. The environmental occurrence of antibiotics has received worldwide attention due to their potential harm to the ecosystem and human health. Research status of antibiotics in the environment field is presented by bibliometrics. Herein, we provided a comprehensive overview on the following important issues: (1) occurrence of antibiotics in different environmental compartments, such as wastewater, surface water, and soil; (2) toxicity of antibiotics toward non-target organisms, including aquatic and terrestrial organisms; (3) current treatment technologies for the degradation and removal of antibiotics, including adsorption, hydrolysis, photodegradation and oxidation, and biodegradation. It was found that macrolides, fluoroquinolones, tetracyclines, and sulfonamides were most frequently detected in the environment. Compared to surface and groundwaters, wastewater contained a high concentration of antibiotic residues. Both antibiotics and their metabolites exhibited toxicity to non-target organisms, especially aquatic organisms (e.g., algae and fish). Fluoroquinolones, tetracyclines, and sulfonamides can be removed through abiotic process, such as adsorption, photodegradation, and oxidation. Fluoroquinolones and sulfonamides can directly undergo biodegradation. Further studies on the chronic effects of antibiotics at environmentally relevant concentrations on the ecosystem were urgently needed to fully understand the hazards of antibiotics and help the government to establish the permissible limits. Biodegradation is a promising technology; it has numerous advantages such as cost-effectiveness and environmental friendliness.

Impact of ciprofloxacin impurities on bacterial growth, antibiotic resistance development and content assays

In addition to active pharmaceutical ingredient (API), antibiotics may contain small amounts of excipients and impurities and be prone to accumulation of degradation products. There has been limited work characterizing how these substances impact bacterial growth and antibiotic resistance development. We investigated how two ciprofloxacin (CIP) impurities, fluoroquinolonic acid (FQA) and ciprofloxacin ethylenediamine analogue (CEA), impact growth and antibiotic resistance in Escherichia coli. Additionally, we investigated how these impurities impact a frequently used API content assay. Both impurities displayed modest antimicrobial activity compared to the CIP API. The effective antimicrobial activity of a medicine containing increased impurity levels may permit bacterial growth and resistance development. Our results also suggest that increasing exposure concentration and duration to CEA and FQA, independent of CIP, can promote antibiotic resistance development. However, at concentrations of 100% and below the MIC of the API, impurities had limited contributions to resistance development compared to the CIP API. From a methodological standpoint, we found that UV spectrophotometry may be inadequate to account for antibiotic impurities or degradation products. This can lead to incorrect estimations of API content and we propose additional multi-wavelength measures when using UV spectrophotometry to help identify impurities or degradation.

Degradation of norfloxacin by hydroxylamine enhanced fenton system: Kinetics, mechanism and degradation pathway

This study demonstrated a fast and efficient degradation of a typical antibiotic norfloxacin (NOR) in a hydroxylamine enhanced Fenton (HA-Fenton) system, which showed a higher catalytic activity over a wider pH range (3.0-9.0). The removal efficiency of NOR was 96% at following conditions: 10 mg/L NOR, 10 μM Fe²⁺, 1.0 mM H₂O₂, 0.4 mM HA and pH 5.0. The degradation rate of NOR in the HA-Fenton system (0.23 min^-1) was 10.9 times of that (0.021 min^-1) in Fenton system. The addition of HA to Fenton system accelerated the conversion of Fe³⁺ to Fe²⁺, leading to the high concentration of ·OH in the HA-Fenton system. Ten degradation transformation products were detected by ultra-performance liquid chromatography tandem quadrupole time of flight mass spectrometer (UPLC-QTOF-MS), consequently, three main degradation steps were proposed, including defluorination, quinolone group transformation, and defluorination and piperazinyl ring opening. Further analyses of NO₃^-, NO₂^- and F^- after the reaction indicated that defluorination process was the crucial degradation step. The HA-Fenton system might offer an efficient alternative for degradation of antibiotics in wastewater.

Antibiotics in wastewater: From its occurrence to the biological removal by environmentally conscious technologies

In this critical review, we explored the most recent advances about the fate of antibiotics on biological wastewater treatment plants (WWTP). Although the occurrence of these pollutants in wastewater and natural streams has been investigated previously, some recent publications still expose the need to improve the detection strategies and the lack of information about their transformation products. The role of the antibiotic properties and the process operating conditions were also analyzed. The pieces of evidence in the literature associate several molecular properties to the antibiotic removal pathway, like hydrophobicity, chemical structure, and electrostatic interactions. Nonetheless, the influence of operating conditions is still unclear, and solid retention time stands out as a key factor. Additionally, the efficiencies and pathways of antibiotic removals on conventional (activated sludge, membrane bioreactor, anaerobic digestion, and nitrogen removal) and emerging bioprocesses (bioelectrochemical systems, fungi, and enzymes) were assessed, and our concern about potential research gaps was raised. The combination of different bioprocess can efficiently mitigate the impacts generated by these pollutants. Thus, to plan and design a process to remove and mineralize antibiotics from wastewater, all aspects must be addressed, the pollutant and process characteristics and how it is the best way to operate it to reduce the impact of antibiotics in the environment.

Enhanced visible-light photodegradation of fluoroquinolone-based antibiotics and E. coli growth inhibition using Ag-TiO2 nanoparticles

Antibiotics in wastewater represent a growing and worrying menace for environmental and human health fostering the spread of antimicrobial resistance. Titanium dioxide (TiO₂) is a well-studied and well-performing photocatalyst for wastewater treatment. However, it presents drawbacks linked with the high energy needed for its activation and the fast electron–hole pair recombination. In this work, TiO₂ nanoparticles were decorated with Ag nanoparticles by a facile photochemical reduction method to obtain an increased photocatalytic response under visible light. Although similar materials have been reported, we advanced this field by performing a study of the photocatalytic mechanism for Ag–TiO₂ nanoparticles (Ag–TiO₂ NPs) under visible light taking in consideration also the rutile phase of the TiO₂ nanoparticles. Moreover, we examined the Ag–TiO₂ NPs photocatalytic performance against two antibiotics from the same family. The obtained Ag–TiO₂ NPs were fully characterised. The results showed that Ag NPs (average size: 23.9 ± 18.3 nm) were homogeneously dispersed on the TiO₂ surface and the photo-response of the Ag–TiO₂ NPs was greatly enhanced in the visible light region when compared to TiO₂ P25. Hence, the obtained Ag–TiO₂ NPs showed excellent photocatalytic degradation efficiency towards the two fluoroquinolone-based antibiotics ciprofloxacin (92%) and norfloxacin (94%) after 240 min of visible light irradiation, demonstrating a possible application of these particles in wastewater treatment. In addition, it was also proved that, after five Ag–TiO₂ NPs re-utilisations in consecutive ciprofloxacin photodegradation reactions, only a photocatalytic efficiency drop of 8% was observed. Scavengers experiments demonstrated that the photocatalytic mechanism of ciprofloxacin degradation in the presence of Ag–TiO₂ NPs is mainly driven by holes and ˙OH radicals, and that the rutile phase in the system plays a crucial role. Finally, Ag–TiO₂ NPs showed also antibacterial activity towards Escherichia coli (E. coli) opening the avenue for a possible use of this material in hospital wastewater treatment.

Ag nanoparticles decorated-TiO₂ P25 are a viable alternative for the degradation, through a rutile-mediated mechanism, of fluoroquinolone-based antibiotics under visible light irradiation and, at the same time, for bacteria inactivation in water.

Water-soluble manganese porphyrins as good catalysts for cipro- and levofloxacin degradation: Solvent effect, degradation products and DFT insights

Synthetic manganese porphyrins (MnPs), in the presence of oxidants, were employed for the degradation of fluoroquinolone antibiotics. Ciprofloxacin (CIP) and levofloxacin (LEV) degradation by iodosylbenzene, iodobenzene diacetate, H₂O₂ and meta-chloroperbenzoic acid using water-soluble MnP catalysts yielded thirteen and nine products, respectively, seven of which have been proposed for the first time. The MnP catalysts have demonstrated the ability to degrade these antibiotics to a high degree (up to 100% degradation). The structures of the degradation products were proposed based on mass spectrometry analysis, and density functional theory calculations could confirm how the substituent moieties attached to the basic chemical structure of the fluoroquinolones influence the degradation reactions. CIP has been shown to be a more reactive substrate towards the porphyrinic catalysts tested because of its three-membered ring. However, the catalysts could almost completely degrade LEV, highlighting the ability of these porphyrins to act as catalysts to degrade environmental pollutants.

Characterization of Lactobacillus reuteri WQ-Y1 with the ciprofloxacin degradation ability

OBJECT

As a broad-spectrum fluoroquinolone antibiotic drug, ciprofloxacin (CIP) is frequently used in the treatment of a wide variety of infections. However, the residues of this antibiotic pose a big threat to the aquatic environment and human health. In this research, Lactobacillus reuteri WQ-Y1 with CIP degradation ability was screened and identified.

RESULTS

L. reuteri WQ-Y1 with a degradation rate of 65.1% for 4 µg mL^-1 CIP was screened from 17 lactic acid bacteria (LAB), and cytochrome P450 enzyme was confirmed to promote the degradation of CIP by L. reuteri WQ-Y1. Meanwhile, the CIP degradation rate were also higher in 48 h' culture time when co-cultured with 1 mg/mL of glucose in the culture media. Furthermore, result also proved that fluoroquinolone antibiotics with the similar piperazine ring structures could be degraded by L. reuteri WQ-Y1.

CONCLUSIONS

L. reuteri WQ-Y1 could degrade fluoroquinolone antibiotics with the similar piperazine ring structure. However, future work still needs to be done on the confirmation of the key enzymes in the cytochrome P450 enzymes family in the biodegradation. The isolated ciprofloxacin-degrading strain L. reuteri WQ-Y1 had a CIP degradation rate of 65.1% at 24 hours, and one biodegradation metabolite was identified and proved to be an important metabolite of CIP from cytochrome P450 enzymes family hydrolysis with UPLC-MS/MS spectrograms approach.

Development and Validation of Stability-Indicating HPLC Methods for the Estimation of Lomefloxacin and Balofloxacin Oxidation Process under ACVA, H2O2, or KMnO4 Treatment. Kinetic Evaluation and Identification of Degradation Products by Mass Spectrometry

The oxidation of lomefloxacin (LOM) and balofloxacin (BAL) under the influence of azo initiator of radical reactions of 4,4′-azobis(4-cyanopentanoic acid) (ACVA) and H₂O₂ was examined. Oxidation using H₂O₂ was performed at room temperature while using ACVA at temperatures: 40, 50, 60 °C. Additionally, the oxidation process of BAL under the influence of KMnO₄ in an acidic medium was investigated. New stability-indicating HPLC methods were developed in order to evaluate the oxidation process. Chromatographic analysis was carried out using the Kinetex 5u XB—C18 100A column, Phenomenex (Torrance, CA, USA) (250 × 4.6 mm, 5 μm particle size, core shell type). The chromatographic separation was achieved while using isocratic elution and a mobile phase with the composition of 0.05 M phosphate buffer (pH = 3.20 adjusted with o-phosphoric acid) and acetonitrile (87:13 v/v for LOM; 80:20 v/v for BAL). The column was maintained at 30 °C. The methods were validated according to the ICH guidelines, and it was found that they met the acceptance criteria. An oxidation process followed kinetics of the second order reaction. The most probable structures of LOM and BAL degradation products formed were assigned by the UHPLC/MS/MS method.

Process type is the key driver of the fate of organic micropollutants during industrial scale treatment of organic wastes

Organic micropollutants (OMPs) such as polycyclic aromatic hydrocarbons, nonylphenols and pharmaceutical products are ubiquitous in organic wastes generated by most human activities. Those wastes are mainly recycled by land spreading, most often after treatments, such as liming, dewatering, composting or anaerobic digestion. It has been shown essentially at lab scales that biological treatments have an effect on the removal of some OMPs. However, less is known on the role of each step of industrial treatment lines combining physico-chemical and biological treatments on the OMP fate and removal. The present study focuses on the impact of waste treatment on the fate of 53 OMPs along 10 industrial treatment lines treating urban, agricultural wastes or mixtures. The combination of studying a diversity of organic wastes and of OMPs with different characteristics (solubility, ionic charges, hydrophobicity etc.), sampling in situ industrial sites, quantifying native OMP concentrations and looking at each step of complete treatment lines allows for a global and representative view of the OMP fate in the French organic waste treatment sector. Less studied wastes, i.e. territorial mixtures, revealed intermediate OMP contents and compositions, between urban and agricultural wastes. Dewatering and liming, usually dismissed, had a noticeable effect on concentrations. Anaerobic digestion and composting had significant effects on the removal of all pollutant families. Combination of processes enhanced most OMP dissipation. Here we showed for the first time that the process type rather than the waste origin affects dissipation of organic micropollutants. Such data could be used to build and validate dynamic models for the fate of OMPs on solid waste treatment plants.

Biodegradation of fluoroquinolone antibiotics and the climbazole fungicide by Trichoderma species

Filamentous fungi Trichoderma have been able to efficiently degrade fluoroquinolone antibiotics namely ciprofloxacin (CIP) and ofloxacin (OFL) as well as the fungicide climbazole (CLB) that are persistent in conventional activated sludge processes. All targeted compounds were biotransformed by whole cells of Trichoderma spp., exactly T. harzanium and T. asperellum, and biosorption played a limited role in their elimination. However, contrasting results were obtained with the two strains. T. asperellum was more efficient against CIP, with a 81% degradation rate in 13 days of incubation, while T. harzianum was more efficient against CLB, with a 91% degradation rate. While in the case of OFL, both strains showed same efficiency with degradation rate around 40%. Adding a cytochrome P450 enzyme inhibitor hardly resulted in the modification of degradation kinetics supporting the implication of extracellular enzymes in chemical biotransformation. Transformation products were identified by liquid chromatography-high resolution-mass spectrometry and transformation pathways were proposed. Biotransformation of selected compounds included hydroxylation, oxidation/reduction and N- and O-dealkylation reactions, similarly to those reported with white rot fungi. CIP underwent transformations at the piperazinyl ring through oxidation and conjugation reactions, while OFL mainly underwent hydroxylation processes and CLB carbonyl reduction into alcohol. Consequently, Trichoderma spp. likely possess a machinery of unspecific enzymes, which makes their application in removal of pharmaceutical and personal care products attractive.

Elucidating biotransformation pathways of ofloxacin in lettuce (Lactuca sativa L)

Antibiotics can be uptaken by plants from soil desorption or directly from irrigation water, but their metabolization pathways in plants are largely unknown. In this paper, an analytical workflow based on high-resolution mass spectrometry was applied for the systematic identification of biotransformation products of ofloxacin in lettuce. The targeted metabolites were selected by comparing the mass chromatograms of exposed with control samples using an advanced spectra-processing method (Fragment Ion Search). The innovative methodology presented allowed us to identify a total of 11 metabolites, including 5 ofloxacin metabolites that are being reported for the first time in plants. Accordingly, major transformation pathways were proposed revealing insight into how ofloxacin and related chemicals are metabolized in lettuce. Furthermore, the influence of biotransformation on potential residual antimicrobial activity of identified compounds was discussed. Human exposure to antibiotics at doses below the minimum inhibitory concentrations is crucial in human risk assessment, including food ingestion; however, in the case of ofloxacin presented results reveal that plant metabolites should also be considered so as not to underestimate their risk.

Revealing the role of adsorption in ciprofloxacin and sulfadiazine elimination routes in microalgae

Pharmaceutical and Personal Care Products (PPCPs) removal coupling with bioenergy production by microalgae has attracted growing attention. However, the biological interactions between PPCPs and microalgae are unclear during microalgal biosorption and biodegradation of PPCPs. In this study, an optimal ciprofloxacin (CIP) and sulfadiazine (SDZ) removal efficiency were achieved 100% and 54.53% with carbohydrate productivity of >1000 mg L^-1 d^-1 by Chlamydomonas sp. Tai-03, respectively. The elimination routes indicated that CIP removal was mainly achieved by biodegradation (65.05%) whereas SDZ was mainly removed by photolysis (35.60%). The visualization evidence of microscopic imaging Raman spectrometer supported the favorable biosorption of CIP due to its positive charge (+10.20 mV). Meanwhile, the tendency for gradual reduction of CIP in extracellular polymeric substances (EPS) indicated that suspended microalgal cell facilitated CIP uptake and biodegradation. Furthermore, photolysis and biodegradation pathways were thoroughly analyzed to demonstrate that intermediates were less toxic and had no adverse effect on the subsequent ethanol conversion. This study provides valuable information for the development of a novel microalgal PPCPs removal. These findings reveal the possible biological mechanisms of biosorption and biodegradation of PPCPs in microalgae, which could further enhance the feasibility of microalgal applications for simultaneous PPCPs remediation and alternative energy production.

Electrochemical degradation of the antibiotic ciprofloxacin in a flow reactor using distinct BDD anodes: Reaction kinetics, identification and toxicity of the degradation products

The performances of distinct BDD anodes (boron doping of 100, 500 and 2500 ppm, with sp³/sp² carbon ratios of 215, 325, and 284, respectively) in the electrochemical degradation of ciprofloxacin - CIP (0.5 L of 50 mg L^-1 in 0.10 M Na₂SO₄, at 25 °C) were comparatively assessed using a recirculating flow system with a filter-press reactor. Performance was assessed by monitoring the CIP and total organic carbon (TOC) concentrations, oxidation intermediates, and antimicrobial activity against Escherichia coli as a function of electrolysis time. CIP removal was strongly affected by the solution pH (kept fixed), flow conditions, and current density; similar trends were obtained independently of the BDD anode used, but the BDD₁₀₀ anode yielded the best results. Enhanced mass transport was achieved at a low flow rate by promoting the solution turbulence within the reactor. The fastest complete CIP removal (within 20 min) was attained at j = 30 mA cm^-2, pH = 10.0, and q_V = 2.5 L min^-1 + bypass turbulence promotion. TOC removal was practically accomplished only after 10 h of electrolysis, with quite similar performances by the distinct BDD anodes. Five initial oxidation intermediates were identified (263 ≤ m/z ≤ 348), whereas only two terminal oxidation intermediates were detected (oxamic and formic acids). The antimicrobial activity of the electrolyzed CIP solution was almost completely removed within 10 h of electrolysis. The characteristics of the BDD anodes only had a marked effect on the CIP removal rate (best performance by the least-doped anode), contrasting with other data in the literature.

Synthetic Mn(III) porphyrins as biomimetic catalysts of CYP450: Degradation of antibiotic norfloxacin in aqueous medium

Norfloxacin (NOR) is a synthetic broad-spectrum fluoroquinolone antibiotic classified as an emerging contaminant. Here, we investigate Mn(III) porphyrin-catalyzed NOR degradation using peroxides or peracids (H₂O₂, t-BuOOH, or Oxone®) as oxidants. We evaluate three Mn(III) porphyrins: the 1^st-generation tetraphenylporphyrin and 2^nd -generation porphyrins bearing halogen atoms at the ortho-positions of the porphyrin macrocycle meso-aryl groups. Experiments were carried out in aqueous medium under mild conditions. NOR degradation was 67%. Products were proposed by mass spectrometry (MS) analysis. Oxone® was the best oxidant for NOR degradation despite its possible decomposition in the reaction medium. The second-generation Mn(III) porphyrins were more resistant than the first-generation Mn(III) porphyrin, indicating that the bulky groups introduced into the porphyrin macrocycle meso-aryl groups led to more robust catalysts. The degradation products did not present cytotoxic behavior under the employed conditions. In conclusion, Mn(III) porphyrin-catalyzed NOR degradation is a promising strategy to degrade fluoroquinolones and other pollutants.

Bacteria-assisted removal of fluoroquinolones from wheat rhizospheres in an agricultural soil

Extensive fluoroquinolone antibiotics use results in their widespread occurrence in various environments including soil, which threatens the soil ecology and public health. The fate of fluoroquinolones in agricultural soil and the efficacy of enhanced degradation in the presence of an agricultural crops and antibiotic degrading bacteria could be better understood. The current study examined ciprofloxacin (CIP), enrofloxacin (ENR), and levofloxacin (LEV) biodegradation in a Maury Silt Loam soil in greenhouse conditions by bacterial-assisted removal of individual and mixed antibiotics in wheat rhizospheres. Fluoroquinolones were added at rates of 5, 50, and 100 mg kg^-1. Three bacterial isolates were applied at 10⁶ CFU g^-1 soil individually and in consortium. Antibiotics appeared in wheat tissue, with more accumulation in roots than shoots. Low recoveries (<50%) of CIP, ENR, and LEV were observed at all levels and treatments in a bacteria and wheat-free control compared to the initial concentrations applied Contaminated soil with wheat had greater antibiotic recovery than the wheat-free control. Antibiotic recovery with bacterial inoculum was less than that of the indigenous bacteria. The least antibiotic recovery occurred with wheat and bacterial inoculum together. At concentrations of 5 and 50 mg kg^-1, but not at 100 mg kg^-1, CIP, ENR, and LEV were below detection limits in soil after 30 days through the combination of wheat and bacteria compared to the control. This synergistic removal of the fluoroquinolone antibiotics is proposed to be due to enhanced antibiotic bioavailability, which suggests it as an environment-friendly approach to biodegradation.

Fate and removal of antibiotics and antibiotic resistance genes in hybrid constructed wetlands

Hybrid design and artificial aeration has been widely applied in wetlands, but little is known about their effectiveness in the removal of antibiotics and antibiotic resistance genes (ARGs). Here we investigated the performance of various mesocosm-scale constructed wetlands (CWs) with artificial aeration and hybrid design in removal of antibiotics and ARGs from antibiotics-spiked domestic sewage. Four hybrid constructed wetland systems with zeolite as substrate and Iris tectorum Maxim as plant were set up to have different artificial aeration designs. The aqueous removal efficiencies of total antibiotics ranged from 87.4% to 95.3%, while those of total ARGs varied from 87.8% to 99.1%. The mass removal of antibiotics by the CWs was attributed mainly to the microbial degradation. The present study imply that sorption of substrates and biological processes could be the two main mechanisms for ARGs elimination. The results from this study showed the hybrid CWs with artificial aeration could enhance treatment efficiencies of antibiotics and ARGs as well as conventional pollutants.

Co-metabolic degradation of the antibiotic ciprofloxacin by the enriched bacterial consortium XG and its bacterial community composition

Ciprofloxacin is a broad spectral and highly refractory antibiotic. It is an emerging pollutant. This study aimed to utilise co-metabolism as a means to degrade ciprofloxacin by a bacterial consortium. The stable bacterial consortium XG capable of efficiently degrading ciprofloxacin was successfully established through successive acclimation of indigenous microorganisms. The consortium XG was primarily consisted of Achromobacter, Bacillus, Lactococcus, Ochrobactrum, and Enterococcus as well as at least other five minor genera. A novel strain YJ17 with CIP-degrading ability was isolated from the consortium and identified as Ochrobactrum sp. The consortium XG utilised amino acids, carbohydrates, and carboxylic acids at a rate approximately 16.6-243-fold greater than the other carbon substrates, but only slow utilisation of ciprofloxacin as a sole carbon source. Ciprofloxacin can be co-metabolized along with many carbon sources, attaining degradation rates up to 63%. Glycyl-l-glutamic acid, d-cellobiose, and itaconic acid are among the substrates most favourable for co-metabolism. The metabolites of ciprofloxacin were identified by LC-QTOF-MS. Co-metabolic degradation of ciprofloxacin by consortium XG led to the removal of essential functional groups from parent compound, thus resulting in formation of metabolites with less bioactive potency. Finally, a possible biochemical pathway for the degradation of ciprofloxacin was proposed. Consortium XG possesses high potential for bioremediation of ciprofloxacin-contaminated environments in the presence of a co-substrate.

Optimization of the electrochemical degradation process of the antibiotic ciprofloxacin using a double-sided β-PbO2 anode in a flow reactor: kinetics, identification of oxidation intermediates and toxicity evaluation

The electrochemical degradation of ciprofloxacin-CIP (50 mg L^-1 in 0.10 mol L^-1 Na₂SO₄) was investigated using a double-sided Ti-Pt/β-PbO₂ anode in a filter-press flow reactor, with identification of oxidation intermediates and follow-up of antimicrobial activity against Escherichia coli. The effect of solution pH, flow rate, current density, and temperature on the CIP removal rate was evaluated. All of these parameters did affect the CIP removal performance; thus, optimized electrolysis conditions were further explored: pH = 10, q_V = 6.5 L min^-1, j = 30 mA cm^-2, and θ = 25 °C. Therefore, CIP was removed within 2 h, whereas ~75% of the total organic carbon concentration (TOC) was removed after 5 h and then, the solution no longer presented antimicrobial activity. When the electrochemical degradation of CIP was investigated using a single-sided boron-doped diamond (BDD) anode, its performance in TOC removal was similar to that of the Ti-Pt/β-PbO₂ anode; considering the higher oxidation power of BDD, the surprisingly good comparative performance of the Ti-Pt/β-PbO₂ anode was ascribed to significantly better hydrodynamic conditions attained in the filter-press reactor used with this electrode. Five initial oxidation intermediates were identified by LC-MS/MS and completely removed after 4 h of electrolysis; since they have also been determined in other degradation processes, there must be similarities in the involved oxidation mechanisms. Five terminal oxidation intermediates (acetic, formic, oxamic, propionic, and succinic acids) were identified by LC-UV and all of them (except acetic acid) were removed after 10 h of electrolysis.

Photoelectrocatalytic degradation of emerging contaminants at WO3/BiVO4 photoanodes in aqueous solution

Advantages and limitations of WO₃/BiVO₄ heterojunctions applied to the photoelectrochemical treatment of some environmental Contaminants of Emerging Concern (CEC).

Persistence of the antibiotic sulfamethoxazole in river water alone or in the co-presence of ciprofloxacin

Sulfamethoxazole and ciprofloxacin are among the most prescribed antibiotics and are frequently detected in surface water ecosystems. The aim of this study was to assess the role of a riverine natural microbial community in sulfamethoxazole (SMX) degradation in presence and absence of ciprofloxacin (CIP). River samples were collected from a stretch of the Tiber River highly impacted by human pressure. An experimental set up was performed varying some abiotic (dark/UV-light) and biotic (presence/absence of microorganisms) conditions that can affect antibiotic degradation. The residual concentrations of SMX and CIP were measured (HPLC-MS or HPLC-UV/FLD) and the effects on the natural microbial community were assessed in terms of microbial number (N. live cells/mL) and structure (Fluorescence In Situ Hybridization - FISH). Finally, the occurrence of the antibiotic resistance sul1 gene was also verified using quantitative PCR (qPCR). In 28 days, in the presence of both UV-light and microorganisms SMX disappeared (<LOD). SMX decreased partially in the dark (24%) and a slightly higher depletion was found in sterile river water and UV-light (30%). However, only in the presence of the microbial populations and in dark conditions, SMX disappeared subsequently at days 60. In the co-presence of CIP and light, SMX was more persistent (50%) than when alone. The depletion of CIP was not negatively influenced by SMX occurrence. The antibiotics did not negatively affect the microbial numbers. The FISH analysis showed that some bacterial populations were initially inhibited by the presence of the antibiotics, but at the end of the experiment, a general increase in most groups was observed together with an increase in the copy numbers of the sul1 gene. Therefore, the antibiotics at the dose of 500 μg/L did not have biocide effects on the natural microbial community and, instead, promoted some resistant natural bacterial populations able to degrade them.

UPLC-MS/MS method validation of ciprofloxacin in human urine: Application to biodegradability study in microbial fuel cell

To enable the reliable quantification of ciprofloxacin in human urine, a sensitive and selective assay based on liquid chromatography-tandem mass spectrometry was developed. The chromatographic separation of the ciprofloxacin was carried out on a Zorbex Eclipse C₁₈ column using methanol and ammonium acetate as a mobile phase by the gradient elution method. The developed assay covered a wide range of concentrations (1.56-100 ng/mL) with a lower limit of detection of 0.76 ng/mL. Quantification was performed using the multiple reaction monitoring transitions 331.8/231 for ciprofloxacin and 362/318 for ofloxacin (internal standard). This assay was validated for linearity, accuracy, precision and recovery. The validated method was then applied to the biodegradability of ciprofloxacin (99%) from human urine in the microbial fuel cell.

Preparation of wheat straw-supported Nanoscale Zero-Valent Iron and its removal performance on ciprofloxacin

Wheat straw-supported Nanoscale Zero-Valent Iron particles (WS-NZVI) were successfully synthesized, which were used for Ciprofloxacin hydrochloride (CIP) removal in simulation wastewater. The structure, chemical composition and micro-morphology of WS-NZVI and Nanoscale Zero-Valent Iron (NZVI) were characterized by scanning electron microscopy analysis (SEM), X-ray diffraction (XRD), as well as the Fourier Transformed IR spectra (FT-IR). XRD results proved the existence of Fe°, and SEM images indicated that the agglomeration of NZVI was effectively inhibited when loaded on wheat straw. Besides, the effects of initial solution pH, CIP concentration, adsorbents dosage and contacting time on the removal efficiency of CIP by WS-NZVI and NZVI were investigated. The experimental results showed that, compared with NZVI and wheat straw, WS-NZVI possessed higher removal efficiency for CIP, and the maximum removal capacity of CIP by WS-NZVI was 363.63 mg g^-1 (25 °C). Furthermore, WS-NZVI was suitable for wider pH range (pH = 4-10) in comparison with NZVI. For the WS-NZVI, the kinetic was better fitted with pseudo-second-order equation, rather than pseudo-first-order equation. The Mass spectrometry (MS) analysis deduced that the degradation reaction mainly occurred on quinolone groups piperazinyl ring. Therefore, it is feasible that using wheat straw as a support material to enhance the performance of NZVI, and the synthesized WS-NZVI has a potential in the organic compounds elimination because of its redox reaction activity.