Biodegradation of antibiotic ciprofloxacin: pathways, influential factors, and bacterial community structure

Functional role of mixed-culture microbe in photocatalysis coupled with biodegradation: Total organic carbon removal of ciprofloxacin

Ciprofloxacin is an extensively used fluoroquinolone antibiotic, which exists in aquatic environment, causing detrimental effects to the aquatic ecosystem and thus, indirectly to humans. Thus, an efficient and rapid removal method for ciprofloxacin is urgently needed. Intimately coupled photocatalysis and biodegradation has proven to be highly efficient, low-cost, and eco-friendly. In this study, cube polyurethane sponges modified with visible light-responsive g-C₃N₄ and mixed culture microbes were used to increase the ciprofloxacin removal efficiency. Subsequently, 94% of ciprofloxacin was removed by photocatalytic-biodegradation and 12 degradation products and possible degradation pathways were analyzed. Photocatalytic-biodegradation had a 1.57 times higher total organic carbon (TOC) removal rate than photocatalytic degradation. The microbial community structure after 72 h of photocatalytic biodegradation was examined. High microbial richness, evenness, and functional dominant species belong to Proteobacteria, which were closely associated with the utilization of antibiotics, may be majorly responsible for the highly efficient removal degradation process. Additionally, microbes retarded the interaction of photogenerated electrons and holes, which may contribute to the increasing mineralization. The findings demonstrated the potential ability of photocatalytic biodegradation in degrading bio-recalcitrant compounds and provide new insights into photocatalytic coupled with biodegradation for removal of ciprofloxacin.

Adsorption/desorption and degradation of doxycycline in three agricultural soils

Veterinary antibiotics are widely used in animal agriculture. Owing to its good absorption in the gastrointestinal tract, strong tissue permeability, and long biological half-life, doxycycline (DOX) is widely used to treat bacterial infections; however, this use can pose an environmental risk. The adsorption/desorption and degradation of DOX in three agricultural soils were investigated. DOX rapidly adsorbed to the soils, with an adsorption equilibrium time of 12 h for the three soils. The Freundlich equation was used to fit the adsorption and desorption of DOX in soils. A high Freundlich affinity coefficient (KF) was obtained from Freundlich isotherms, indicating strong sorption of DOX to agricultural soils and weak mobility to aquatic environment. Soil organic matter, the clay ratio and the cation exchange capacity were significantly positively correlated with KF (P < 0.05). The half-life (DT50) of DOX degradation in the soils ranged from 2.51 to 25.52 d. Soil microorganisms, soil moisture, temperature, the initial concentration, illumination and soil texture all significantly affected the degradation of DOX in soil (P < 0.05). When 8% (w/w) manure was added, DOX degradation was significantly accelerated (P < 0.05). Biotic and abiotic factors affected the degradation of DOX in soils. These results indicated that soil properties and environmental conditions greatly affected the fate and transport of DOX into agricultural soils.

Electrocatalytic oxidation of ciprofloxacin by Co-Ce-Zr/γ-Al2O3 three-dimensional particle electrode

In this work, Co-Ce-Zr/γ-Al₂O3₃ particle electrodes were prepared for the efficient degradation of ciprofloxacin (CIP). Co-Ce-Zr/γ-Al₂O₃ particle electrodes were analyzed with a scanning electron microscope (SEM), X-Ray Diffraction (XRD), X-Ray Fluorescence Spectrometer (XRF), X-ray photoelectron spectroscopy (XPS), and energy-dispersive X-ray spectroscopy (EDS). According to the results, significant amounts of Co₃O₄, CeO₂, and ZrO₂ were formed on the Co-Ce-Zr/γ-Al₂O₃ particle electrodes. It was shown that when the conditions of the reaction system were at pH=6, conductivity of 4 ms/cm, current of 0.2 A, initial pollutant concentration of 100 mg/L, and material dosage of 15 g, CIP could be completely degraded within 40 min, and the energy consumed in the reaction was 41.3 kWh/kg CIP. The rate of total organic carbon (TOC) removal by Co-Ce-Zr/γ-Al₂O₃ particle electrodes was recorded to be approximately 52.6%. Using a response surface methodology, we explored the optimal operating conditions. At the same time, we also explored the influence of inorganic anions in water and actual water medium on the rate of CIP removal. In addition, the ESR data proved that the main active substance in the reaction system was ·OH. The degradation intermediates were investigated, and the possible mechanism was proposed. Thus, this research provided a new solution for the treatment of antibiotic-containing wastewater.

Preparation of Fe-MIL(100)-encapsulated magnetic g-C3N4 for adsorption of PPCPs from aqueous solution

In the present work, the Fe-MIL(100) was encapsulated on the outer surface of magnetic g-C₃N₄ through a simple method to synthesize a novel adsorbent. The as-prepared g-C₃N₄/MnFe₂O₄/Fe-MIL(100) was characterized with scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), BET specific surface area (BET), vibrating sample magnetometry (VSM), and plasma emission spectrometry (PES). The g-C₃N₄/MnFe₂O₄/Fe-MIL(100) possessed rough surface, large surface area (303.68 m²/g), mesoporous structure and magnetic properties, which exhibited excellent adsorption performance for ciprofloxacin (CIP), oxytetracycline (OTC) and indomethacin (IDM) with the maximum adsorption capacities reaching up to 45.51, 64.34 and 103.91 mg/g, respectively. The adsorption processes of all three PPCPs could be described by different kinds of isotherms and kinetic models. Additionally, the adsorption capacity of the resulting adsorbent could maintain 73.43% of the first adsorption capacity even after ten cycles. Finally, the possible adsorption mechanisms of g-C₃N₄/MnFe₂O₄/Fe-MIL(100) for CIP/OTC/IDM were proposed. Thus, g-C₃N₄/MnFe₂O₄/Fe-MIL(100) possessed excellent features of high adsorption capacity, fast removal rate, easy synthesis, salt resistance and magnetic separation, which showed great potential application to be used as an effective adsorbent for adsorptive removal of PPCPs in wastewater.

Anaerobic biodegradation of levofloxacin by enriched microbial consortia: Effect of electron acceptors and carbon source

For improving the understanding of anaerobic degradation mechanism of fluoroquinolone antibiotics (FQs), the degradation of a representative FQs, levofloxacin (LEV), by six enriched anaerobic consortia were explored in this study. The effect of sulfate and nitrate as the electron acceptor and glucose as the carbon source on LEV anaerobic degradation were investigated. Addition of glucose and nitrate alone deteriorated LEV removal from 36.5% to 32.7% and 29.1%, respectively. Addition of sulfate slightly improved LEV removal to 39.6%, while simultaneous addition of glucose and sulfate significantly enhanced LEV removal to 53.1%. Twelve biodegradation intermediates were identified, which indicated that cleavage of piperazine ring is prior to that of quinolone ring, and hydroxylation, defluorination, demethylation, and decarboxylation were the primary steps of LEV anaerobic degradation. Lactobacillus, unclassified _f_Enterobacteriaceae, and Bacillus were enriched by simultaneous addition of glucose and sulfate, with relative abundance of 63.5%, 32.7%, and 3.3%, respectively. The predicted high gene abundance of xenobiotics biodegradation & metabolism, carbohydrate metabolism, and assimilatory sulfate reduction in the consortium, indicated a co-metabolism between carbohydrate metabolism, sulfate metabolism, and LEV degradation under glucose and sulfate added condition. The study revealed that simultaneous addition of glucose and sulfate is the favorable condition for LEV anaerobic degradation.

Complete Degradation and Detoxification of Ciprofloxacin by a Micro-/Nanostructured Biogenic Mn Oxide Composite from a Highly Active Mn2+-Oxidizing Pseudomonas Strain

Ciprofloxacin (CIP), as a representative broad-spectrum antibiotic, poses a major threat to human health and the ecological environment as a result of its abuse and emissions. In this study, a highly active Mn²⁺-oxidizing bacterium, Pseudomonas sp. CCTCC M2014168, was induced to form micro-/nanostructured biogenic Mn oxide (BMO) aggregates through continuous culturing with 1 mmoL^-1 Mn²⁺. Following the characterization of Mn⁴⁺ oxides and the micro-/nanostructures by scanning electron microscopy, high-resolution transmission electron microscopy and X-ray diffraction assays, the BMO composites were subjected to CIP degradation and detoxification in laboratory trials. High-performance liquid chromatograph (HPLC) analysis identified that the BMO composites were capable of completely degrading CIP, and HPLC with a mass spectrometer (LC/MS) assays identified three intermediates in the degradation pathway. The reaction temperature, pH and initial ciprofloxacin concentration substantially affected the degradation efficiency of CIP to a certain extent, and the metal ions Mg²⁺, Cu²⁺, Ni²⁺ and Co²⁺ exerted significant inhibitory effects on CIP degradation. A toxicity test of the degradation products showed that CIP was completely detoxified by degradation. Moreover, the prepared BMO composite exhibited a high capacity for repeated degradation and good performance in continuous degradation cycles, as well as a high capacity to degrade CIP in real natural water.

Electrolysis-sulfate-reducing up-flow sludge bed-biological contact oxidation reactor for Norfloxacin removal from wastewater with high sulfate content

This study investigated the treatment of 100-mg/L Norfloxacin (NOR) wastewater containing high concentrations of sulfate through a combination of electrolysis, sulfate-reducing up-flow sludge bed (SRUSB), and biological contact oxidation reactor (BCOR) treatments. Results revealed that after 62 h, the reaction system had processed over 97% of the NOR. Additionally, electrolysis with sodium sulfate as the electrolyte transformed 87.8% of the NOR but only 33.5% of the total organic carbon (TOC). In the SRUSB, the TOC and SO₄^2- contents were simultaneously reduced by 87.4% and 95.6%, respectively, providing a stable environment to the BCOR. In the BCOR, 36.3% and 85.9% of the NOR and TOC were degraded. High-performance liquid chromatography-tandem mass spectrometry analysis identified three possible degradation pathways under the attack of -OH during electrolysis, including defluorination, piperazinyl ring transformation, and quinolone ring transformation. Furthermore, the Illumina HiSeq sequencing results demonstrated that the sulfate-reducing bacteria (represented by Desulfobacter and Desulfobulbus) in the SRUSB and the sulfate-oxidizing bacteria (mainly consisting of Gammaproteobacteria and Alphaproteobacteria) in the BCOR played important roles in carbon chain oxidation and benzene ring opening and thoroughly degraded the electrolysis products. Thus, this method effectively overcomes the incomplete degradation and low removal efficiency issues associated with single electrolysis or biological methods in traditional processes.

Anaerobic Digestion and Removal of Sulfamethoxazole, Enrofloxacin, Ciprofloxacin and Their Antibiotic Resistance Genes in a Full-Scale Biogas Plant

Anaerobic digestion is one of the best ways to re-use animal manure and agricultural residues, through the production of combustible biogas and digestate. However, the use of antibiotics for preventing and treating animal diseases and, consequently, their residual concentrations in manure, could introduce them into anaerobic digesters. If the digestate is applied as a soil fertilizer, antibiotic residues and/or their corresponding antibiotic resistance genes (ARGs) could reach soil ecosystems. This work investigated three common soil emerging contaminants, i.e., sulfamethoxazole (SMX), ciprofloxacin (CIP), enrofloxacin (ENR), their ARGs sul1, sul2, qnrS, qepA, aac-(6′)-Ib-cr and the mobile genetic element intI1, for one year in a full scale anaerobic plant. Six samplings were performed in line with the 45-day hydraulic retention time (HRT) of the anaerobic plant, by collecting input and output samples. The overall results show both antibiotics and ARGs decreased during the anaerobic digestion process. In particular, SMX was degraded by up to 100%, ENR up to 84% and CIP up to 92%, depending on the sampling time. In a similar way, all ARGs declined significantly (up to 80%) in the digestate samples. This work shows how anaerobic digestion can be a promising practice for lowering antibiotic residues and ARGs in soil.

Detoxification of Ciprofloxacin in an Anaerobic Bioprocess Supplemented with Magnetic Carbon Nanotubes: Contribution of Adsorption and Biodegradation Mechanisms

In anaerobic bioreactors, the electrons produced during the oxidation of organic matter can potentially be used for the biological reduction of pharmaceuticals in wastewaters. Common electron transfer limitations benefit from the acceleration of reactions through utilization of redox mediators (RM). This work explores the potential of carbon nanomaterials (CNM) as RM on the anaerobic removal of ciprofloxacin (CIP). Pristine and tailored carbon nanotubes (CNT) were first tested for chemical reduction of CIP, and pristine CNT was found as the best material, so it was further utilized in biological anaerobic assays with anaerobic granular sludge (GS). In addition, magnetic CNT were prepared and also tested in biological assays, as they are easier to be recovered and reused. In biological tests with CNM, approximately 99% CIP removal was achieved, and the reaction rates increased ≈1.5-fold relatively to the control without CNM. In these experiments, CIP adsorption onto GS and CNM was above 90%. Despite, after applying three successive cycles of CIP addition, the catalytic properties of magnetic CNT were maintained while adsorption decreased to 29 ± 3.2%, as the result of CNM overload by CIP. The results suggest the combined occurrence of different mechanisms for CIP removal: adsorption on GS and/or CNM, and biological reduction or oxidation, which can be accelerated by the presence of CNM. After biological treatment with CNM, toxicity towards Vibrio fischeri was evaluated, resulting in ≈ 46% detoxification of CIP solution, showing the advantages of combining biological treatment with CNM for CIP removal.

Alkylphenols and Chlorophenols Remediation in Vertical Flow Constructed Wetlands: Removal Efficiency and Microbial Community Response

This study aims to investigate the effect of two different groups of phenolic compounds (the alkylphenols nonylphenol (NP) and octylphenol (OP), and the chlorophenol pentachlorophenol (PCP)) on constructed wetlands (CWs) performance, including on organic matter, nutrients and contaminants removal efficiency, and on microbial community structure in the plant bed substrate. CWs were assembled at lab scale simulating a vertical flow configuration and irrigated along eight weeks with Ribeira de Joane (an urban stream) water not doped (control) or doped with a mixture of NP and OP or with PCP (at a 100 μg·L−1 concentration each). The presence of the phenolic contaminants did not interfere in the removal of organic matter or nutrients in CWs in the long term. Removals of NP and OP were >99%, whereas PCP removals varied between 87% and 98%, mainly due to biodegradation. Microbial richness, diversity and dominance in CWs substrate were generally not affected by phenolic compounds, with only PCP decreasing diversity. Microbial community structure, however, showed that there was an adaptation of the microbial community to the presence of each contaminant, with several specialist genera being enriched following exposure. The three more abundant specialist genera were Methylotenera and Methylophilus (methylophilaceae family) and Hyphomicrobium (hyphomicrobiaceae family) when the systems were exposed to a mixture of NP and OP. When exposed to PCP, the three more abundant genera were Denitromonas (Rhodocyclaceae family), Xenococcus_PCC_7305 (Xenococcaceae family) and Rhodocyclaceae_uncultured (Rhodocyclaceae family). To increase CWs efficiency in the elimination of phenolic compounds, namely PCP which was not totally removed, strategies to stimulate (namely biostimulation) or increase (namely bioaugmentation) the presence of these bacteria should be explore. This study clearly shows the potential of vertical flow CWs for the removal of phenolic compounds, a still little explored subject, contributing to promote the use of CWs as nature-based solutions to remediate water contaminated with different families of persistent and/or emergent contaminants.

Perspectives on the antibiotic contamination, resistance, metabolomics, and systemic remediation

Antibiotics have been regarded as the emerging contaminants because of their massive use in humans and veterinary medicines and their persistence in the environment. The global concern of antibiotic contamination to different environmental matrices and the emergence of antibiotic resistance has posed a severe impact on the environment. Different mass-spectrometry-based techniques confirm their presence in the environment. Antibiotics are released into the environment through the wastewater steams and runoff from land application of manure. The microorganisms get exposed to the antibiotics resulting in the development of antimicrobial resistance. Consistent release of the antibiotics, even in trace amount into the soil and water ecosystem, is the major concern because the antibiotics can lead to multi-resistance in bacteria which can cause hazardous effects on agriculture, aquaculture, human, and livestock. A better understanding of the correlation between the antibiotic use and occurrence of antibiotic resistance can help in the development of policies to promote the judicious use of antibiotics. The present review puts a light on the remediation, transportation, uptake, and antibiotic resistance in the environment along with a novel approach of creating a database for systemic remediation, and metabolomics for the cleaner and safer environment.

Carboxylated cellulose nanofiber/montmorillonite nanocomposite for the removal of levofloxacin hydrochloride antibiotic from aqueous solutions

Herein, we report the facile two-step synthesis of an effective carboxylated cellulose nanofiber/montmorillonite nanocomposite (CMNFs-MMT) adsorbent for levofloxacin hydrochloride (Levo-HCl). CMNFs-MMT was characterized using scanning electron microscopy, energy dispersive X-ray spectrometry, Brunauer-Emmett-Teller measurements, X-ray photoelectron spectroscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. Based on the central composite design, the effects of various factors on the removal of Levo-HCl by the CMNFs-MMT were explored, wherein the effect of pH was the most significant. To gain a clearer perspective on the adsorption process of Levo-HCl onto CMNFs-MMT, the adsorption kinetics and isotherms were also measured, revealing that the reaction is pseudo-second-order and the Sips models provide the best fit with experimental data. Comparing the adsorption in pure water with the removal in river water, the rate of river water removal (90.37%) was slightly lower than that of pure water (93.97%) when adsorption equilibrium was reached, confirming that CMNFs-MMT is not easily influenced by environmental conditions. Reusability experiments indicate that CMNFs-MMT can maintain a certain adsorption capacity for Levo-HCl after six uses. Overall, this work indicates that CMNFs-MMT is an effective adsorbent for eliminating Levo-HCl from aqueous media in future engineering applications.

Enhanced removal of ciprofloxacin and reduction of antibiotic resistance genes by earthworm Metaphire vulgaris in soil

Antibiotic residues could promote the dissemination of antibiotic resistance genes (ARGs) in the environments, and biodegradation represent a major route for antibiotic removal. Previous studies have showed that earthworm could enhance the degradation of certain organic contaminants, however, its effectiveness in ciprofloxacin removal and ARG reduction in soil remains unclear. In the present study, high-performance liquid chromatography, 16S rRNA gene sequencing and high-throughput quantitative PCR were employed to explore the effects of earthworm addition on ciprofloxacin removal and ARG abundance in ciprofloxacin-amended soil. Ciprofloxacin removal was significantly higher in earthworm cast as compare to control soil, and ARG abundance in earthworm cast was significantly lower than that of control soil. Procrustes analysis together with Mantel test showed that the ARG profiles were strongly associated with bacterial communities, indicating that the lower abundance of ARGs in cast samples could be attributed to changes in bacterial community compositions by earthworm activity. Flavobacterium and Turicibacter were enriched in cast samples, which were negatively correlated with ciprofloxacin concentration (p < 0.05), implying their potential roles in ciprofloxacin removal. These results suggested that earthworm gut is a hotspot for ciprofloxacin removal, and could be an option for mitigation of antibiotic pollution in soil.

Adsorption Characteristics of Synthesized Polyelectrolytes onto Alumina Nanoparticles and their Application in Antibiotic Removal

The present study aims to investigate the adsorption of synthesized poly(2-acrylamide-2-methylpropane sulfonic acid) (PAMPs) onto alumina nanoparticles and their application in the removal of ciprofloxacin (CFX) antibiotic from a water environment. The PAMPs were successfully synthesized and characterized by nuclear magnetic resonance and gel-permeation chromatography methods. The number- and weight-average molecular weights of PAMPs were 6.76 × 10⁵ and 7.28 × 10⁶ g/mol, respectively. The charge reversal of nanoalumina after PAMPs modification from positive to -37.5 mV was determined by ζ-potential measurement, while the appearance of C ═ O and N-H functional groups in PAMPs observed by Fourier-transform infrared spectroscopy confirmed them as the main indicators for adsorption of PAMPs onto a nanoalumina surface. The maximum adsorption capacity of PAMPs onto nanoalumina in 100 mg/L KCl was about 10 mg/g. The adsorption isotherms were fitted well by a two-step adsorption model. Application of PAMPs-modified nanoalumina (PAMNA) in CFX removal was also thoroughly studied. The optimum conditions for CFX removal using PAMNA were found to be pH 6, 10 mM NaCl, contact time 90 min, and adsorption dosage 5 mg/mL. The CFX adsorption isotherms and kinetics were in accordance with the two-step and pseudo-second-order models, respectively. The application for CFX removal in actual hospital wastewater was greater than 80%. The results of this study demonstrate that PAMNA is a new and promising material for antibiotic removal from wastewater.

Fate of antibiotics and antibiotic resistance genes during conventional and additional treatment technologies in wastewater treatment plants

Information on the removal of antibiotics and ARGs in full-scale WWTPs (with or without additional treatment technology) is limited. However, it is important to understand the efficiency of full-scale treatment technologies in removing antibiotics and ARGs under a variety of conditions relevant for practice to reduce their environmental spreading. Therefore, this study was performed to evaluate the removal of antibiotics and ARGs in a conventional wastewater treatment plant (WWTP A) and two full-scale combined with additional treatment technologies. WWTP B, a conventional activated sludge treatment followed by an activated carbon filtration step (1-STEP® filter) as a final treatment step. WWTP C, a treatment plant using aerobic granular sludge (NEREDA®) as an alternative to activated sludge treatment. Water and sludge were collected and analysed for 52 antibiotics from four target antibiotic groups (macrolides, sulfonamides, quinolones, tetracyclines) and four target ARGs (ermB, sul 1, sul 2 and tetW) and integrase gene class 1 (intI1). Despite the high removal percentages (79-88%) of the total load of antibiotics in all WWTPs, some antibiotics were detected in the various effluents. Additional treatment technology (WWTP C) showed antibiotics removal up to 99% (tetracyclines). For ARGs, WWTP C reduced 2.3 log followed by WWTP A with 2.0 log, and WWTP B with 1.3 log. This shows that full-scale WWTP with an additional treatment technology are promising solutions for reducing emissions of antibiotics and ARGs from wastewater treatment plants. However, total removal of the antibiotics and ARGS cannot be achieved for all types of antibiotics and ARGs. In addition, the ARGs were more abundant in the sludge compared to the wastewater effluent suggesting that sludge is an important reservoir representing a source for later ARG emissions upon reuse, i.e. as fertilizer in agriculture or as resource for bioplastics or bioflocculants. These aspects require further research.

Nitric oxide reactivity accounts for N-nitroso-ciprofloxacin formation under nitrate-reducing conditions

The formation of N-nitroso-ciprofloxacin (CIP) was investigated both in wastewater treatment plants including nitrification/denitrification stages and in sludge slurry experiments under denitrifying conditions. The analysis of biological wastewater treatment plant effluents by Kendrick mass defect analysis and liquid chromatography - high resolution - mass spectrometry (LCHRMS) revealed the occurrence of N-nitroso-CIP and N-nitroso-hydrochlorothiazide at concentration levels of 34 ± 3 ng/L and 71 ± 6 ng/L, respectively. In laboratory experiments and dark conditions, produced N-nitroso-CIP concentrations reached a plateau during the course of biodegradation experiments. A mass balance was achieved after identification and quantification of several transformation products by LCHRMS. N-nitroso-CIP accounted for 14.3% of the initial CIP concentration (20 µg/L) and accumulated against time. The use of 4,5-diaminofluorescein diacetate and superoxide dismutase as scavengers for in situ production of nitric oxide and superoxide radical anion respectively, revealed that the mechanisms of formation of N-nitroso-CIP likely involved a nitrosation pathway through the formation of peroxynitrite and another one through codenitrification processes, even though the former one appeared to be prevalent. This work extended the possible sources of N-nitrosamines by including a formation pathway relying on nitric oxide reactivity with secondary amines under activated sludge treatment.

Effect of the C/N Ratio on Biodegradation of Ciprofloxacin and Denitrification from Low C/N Wastewater as Assessed by a Novel 3D-BER System

Emerging pollutants in the form of pharmaceuticals have drawn international attention during the past few decades. Ciprofloxacin (CIP) is a common drug widely found in effluents from hospitals, industrial and different wastewater treatment plants, as well as rivers. In this work, the lab-scale 3D-BER system was established, and more than 90% of the antibiotic CIP was removed from Low C/N wastewater. The best results were obtained with the current intensity being taken into account, and a different C/N ratio significantly improved the removal of CIP and nitrates when the ideal conditions were C/N = 1.5–3.5, pH = 7.0–7.5 and I = 60 mA. The highest removal efficiency occurred when CIP = 94.2%, NO3−-N = 95.5% and total nitrogen (TN) = 84.3%, respectively. In this novel system, the autotrophic-heterotrophic denitrifying bacteria played a vital role in the removal of CIP and an enhanced denitrification process. Thus, autotrophic denitrifying bacteria uses CO2 and H2 as carbon sources to reduce nitrates to N2. This system has the assortment and prosperous community revealed at the current intensity of 60 mA, and the analysis of bacterial community structure in effluent samples fluctuates under different conditions of C/N ratios. Based on the results of LC-MS/MS analysis, the intermediate products were proposed after efficient biodegradation of CIP. The microbial community on biodegrading was mostly found at phylum, and the class level was dominantly responsible for the NO3−-N and biodegradation of CIP. This work can provide some new insights towards the biodegradation of CIP and the efficient removal of nitrates from low C/N wastewater treatment through the novel 3D-BER system.

Strong impact of micropollutants on prokaryotic communities at the horizontal but not vertical scales in a subtropical reservoir, China

Micropollutants have become of great concern, because of their disrupting effects on the structure and function of microbial communities. However, little is known about the relative importance of trace micropollutants on the aquatic prokaryotic communities as compared to the traditional physico-chemical characteristics, especially at different spatial dimensions. Here, we investigated free-living (FL) and particle-associated (PA) prokaryotic communities in a subtropical water reservoir, China, across seasons at horizontal (surface water) and vertical (depth-profile) scales by using 16S rRNA gene amplicon sequencing. Our results showed that the shared variances of physico-chemicals and micropollutants explained majority of the spatial variations in prokaryotic communities, suggesting a strong joint effect of the two abiotic categories on reservoir prokaryotic communities. Micropollutants appeared to exert strong independent influence on the core sub-communities (i.e., abundant and wide-spread taxa) than on the satellite (i.e., less abundant and narrow-range taxa) counterparts. The pure effect of micropollutants on both core and satellite sub-communities from FL and PA fractions was ~1.5 folds greater than that of physico-chemical factors at the horizontal scale, whereas an opposite effect was observed at the vertical scale. Moreover, eight micropollutants including anti-fungal agents, antibiotics, bisphenol analogues, stimulant and UV-filter were identified as the major disrupting compounds with strong associations with core taxa of typical freshwater prokaryotes. Altogether, we concluded that the ecological disrupting effects of micropollutants on prokaryotic communities may vary along horizontal and vertical dimensions in freshwater ecosystems.

Ciprofloxacin adsorption by biochar derived from co-pyrolysis of sewage sludge and bamboo waste

Antibiotics residues in aqueous environment and sewage sludge accumulation have become serious environmental issues. The aim of this study is to investigate the potential of ciprofloxacin (CIP) removal by sludge-based biochar prepared from co-pyrolysis of sewage sludge and bamboo waste (BW). The stability and environmental risk of heavy metals (HMs) in the biochar were further investigated to evaluate potential risks for biochar utilization. Results showed that BW was an outstanding additive to prepare co-pyrolyzed biochar from sludge. A higher CIP removal rate (95%) of BW-sludge biochar (SBC) was obtained under initial CIP concentration of 10 mg/L, and its maximum adsorption capacity was 62.48 mg/g which was calculated from the Langmuir model. The pseudo-second-order and Freundlich model also well fit the CIP adsorption process, indicating a chemical and multilayer adsorption of CIP on a heterogeneous surface of biochar. Adsorption mechanism analysis indicated that the diverse functional groups and Fe species in biochar probably were the dominant factors in the adsorption of CIP. The π-π interaction, H-bond, ion exchange, and Fe-complexation might be the main interactions between the functional species and CIP molecules. Besides, HMs, especially the Cr, Cd, and As, were well immobilized in SBC compared with pure sludge biochar. This work suggested that sludge-based biochar, especially the co-pyrolyzed SBC, could be a potential adsorbent for CIP removal from aqueous solutions.

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.

Fate of antibiotics, antibiotic-resistant bacteria, and cell-free antibiotic-resistant genes in full-scale membrane bioreactor wastewater treatment plants

The removal of antibiotics, antibiotic-resistant bacteria (ARB), and cell-free antibiotic-resistant genes (ARGs) and the microbial community of ARB were investigated in detail to understand their fate and provide valuable information on the feasibility of full-scale membrane bioreactor (MBR). The potential risks of cell-free ARGs to the receiving environment were discovered. High influent antibiotic concentration could inhibit the microbial activity of MBR sludge, whereas good antibiotic removal could be maintained because of relatively long solid retention time and high biomass retention. Approximately 61.8%-77.5% of the total antibiotics were degraded, and 22.5%-38.2% of the total antibiotics were adsorbed by MBR sludge on average. The individual antibiotic removal presented intense discrepancy because of the chemical construction and distribution coefficient of antibiotics. Aeromonas exhibited specific antibiotic resistance to ampicillin and erythromycin, Escherichia became the predominant genera in kanamycin-ARB and tetracycline-ARB, and Klebsiella and Bacteroides were the particular genera that exhibited distinct antibiotic resistance to ciprofloxacin. A significant correlation was found between cell-free ARG abundance and ARB content, and relatively high effluent cell-free ARG abundance facilitated the proliferation and transmission of ARB. The impacts of the receiving environment to eliminate the ecological risks and severe threats to human health should be investigated because of the low decay ratio and long-term persistence of cell-free ARGs.

Isolation and Characterization of Ochrobactrum tritici for Penicillin V Potassium Degradation

Substantial concentrations of penicillin V potassium (PVK) have been found in the environment, which may pose potential threats to human health and contribute to the emergence of penicillin-resistant bacterial strains. In this study, antibiotic-degrading bacterial strains for PVK were isolated from sludge and characterized. Ochrobactrum tritici was selected for the biodegradation of PVK with high efficiency. To enhance its PVK degradation ability, a whole-cell biodegradation process was established and optimized using Ochrobactrum tritici. The degradation rate with 0.5 mg/ml PVK reached 100% within 3 h. The potential biodegradation pathway was also investigated. To the best of our knowledge, the present study provides new insights into the biodegradation of PVK using an Ochrobactrum tritici strain, a promising candidate strain for the industrial biodegradation of β-lactam antibiotics.

Substantial concentrations of penicillin V potassium (PVK) have been found in livestock manure, soil, and wastewater effluents, which may pose potential threats to human health and contribute to the emergence of penicillin-resistant bacterial strains. In this study, bacterial strains capable of degrading PVK were isolated from sludge and characterized. Strain X-2 was selected for biodegradation of PVK. Based on morphological observations and 16S rRNA gene sequencing, strain X-2 was identified as an Ochrobactrum tritici strain. To enhance the PVK degradation ability of PVK, a whole-cell biodegradation process of Ochrobactrum tritici X-2 was established and optimized. In the whole-cell biodegradation process, the optimal temperature and pH were 30°C and 7.0, respectively. Under the optimized conditions, the degradation rate using 0.5 mg/ml PVK reached 100% within 3 h. During biodegradation, two major metabolites were detected: penicilloic acid and phenolic acid. The present study provides a novel method for the biodegradation of PVK using Ochrobactrum tritici strains, which represent promising candidates for the industrial biodegradation of PVK.

IMPORTANCE Substantial concentrations of penicillin V potassium (PVK) have been found in the environment, which may pose potential threats to human health and contribute to the emergence of penicillin-resistant bacterial strains. In this study, antibiotic-degrading bacterial strains for PVK were isolated from sludge and characterized. Ochrobactrum tritici was selected for the biodegradation of PVK with high efficiency. To enhance its PVK degradation ability, a whole-cell biodegradation process was established and optimized using Ochrobactrum tritici. The degradation rate with 0.5 mg/ml PVK reached 100% within 3 h. The potential biodegradation pathway was also investigated. To the best of our knowledge, the present study provides new insights into the biodegradation of PVK using an Ochrobactrum tritici strain, a promising candidate strain for the industrial biodegradation of β-lactam antibiotics.

Effects of ciprofloxacin on metabolic activity and algal biomass of urban stream biofilms

Pharmaceuticals and personal care products (PPCPs), such as the commonly prescribed antibiotic ciprofloxacin, are present and persistent in freshwaters, yet their effects on aquatic ecosystem functions at environmentally-relevant concentrations are rarely explored. Stream biofilms provide multiple functions in stream ecosystems, but their functional response to PPCP contaminants such as ciprofloxacin is unclear. To establish the effect of ciprofloxacin on aquatic biofilms, we colonized biofilms in situ on tiles (n = 80) at four sites along an urban stream in Gainesville, Florida, including two sites above and two sites below a wastewater treatment plant (WWTP). We then incubated the tiles and associated biofilms in the laboratory for 6 d exposing biofilms to either 0, 0.01, 0.1, or 1.0 μg/L (target concentrations) of ciprofloxacin. At the end of the 6 d laboratory exposure, we quantified gross primary production (GPP), respiration (R), and biomass (as chlorophyll a) of biofilms, and calculated response ratios for each response. All response metrics were significantly differed across sites (p < 0.01). Ciprofloxacin significantly decreased GPP (p < 0.05) regardless of treatment concentration, most notably at the site immediately below the WWTP, where there was no measurable GPP on any ciprofloxacin-treated biofilms. In contrast, respiration (R) was not significantly affected by ciprofloxacin, despite an apparent increase in R at the WWTP site. However, the WWTP site R was significantly different from the most upstream and downstream sites (p < 0.001) but was not significantly different from a nearby site upstream of the WWTP (p > 0.05). These results indicate that chronic exposure to ciprofloxacin through WWTP effluent can alter ecosystem functions performed by biofilms, which can have consequences for higher trophic levels and stream processes. By quantifying biofilm metabolic responses to ciprofloxacin exposure, this study supports the concept that pharmaceuticals and personal care products can induce sub-lethal effects on ecological processes at environmentally-relevant concentrations.

Effect of the coexposure of sulfadiazine, ciprofloxacin and zinc on the fate of antibiotic resistance genes, bacterial communities and functions in three-dimensional biofilm-electrode reactors

Three-dimensional biofilm electrode reactors (3D-BERs) with high treatment efficiency were constructed to treat wastewater containing sulfadiazine (SDZ) and ciprofloxacin (CIP) coexposure with Zinc (Zn). The results showed that coexposure to target antibiotics and Zn increased the absolute and relative abundances of target antibiotic resistance genes (ARGs). Additionally, the target ARG abundances were higher on cathode of 3D-BER compared with ordinary anaerobic reactor while the abundances of total ARGs were decreased in the effluent. Meanwhile, redundancy analysis results revealed that the composition of bacteria carrying ARGs was greatly influenced in the cathode by the accumulation of Zn and antibiotic, which dominated the changes of ARG abundances. Additionally, ARGs with their host bacteria revealed by network analysis were partially deposited on electrode substrates when being removed from wastewater. Thus, 3D-BER exhibits capability of simultaneously eliminating antibiotic and Zn, and greatly reduces the risks of ARGs spread.

Current progress in the adsorption, transport and biodegradation of antibiotics in soil

Antibiotic residues in soil may cause potential risks to human health and soil ecosystems. To avoid these potential risks, comprehensive study of the adsorption, transport and biodegradation of antibiotics in soil is very imperative. This review provided current views about the most recent studies, which have been conducted toward the adsorption, transport and biodegradation of antibiotics in soil. The influencing factors affecting the adsorption behaviors of antibiotics in soil, including the antibiotics properties (e.g., molecular structure, hydrophobicity, polarity, polarizability, and spatial configuration) and the soil characteristics (e.g., soil type, soil pH, coexisting ions, and soil organic matter), were discussed. The effects of fertilizer colloids, porous media, and pH of soil on the transport behaviors of antibiotics were analyzed. The biodegradation of antibiotics in soil were also highlighted by investigating the effects of soil microbiome, soil pH, soil temperature, and interactions between antibiotics. Prospects of antibiotics adsorption, transport and biodegradation were also proposed.

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.

Fate and removal of Ciprofloxacin in an anaerobic membrane bioreactor (AnMBR)

This study examined the removal of varying concentrations of the antibiotic Ciprofloxacin (CIP) over the long-term (120 days) in an anaerobic membrane bioreactor (AnMBR). The results showed that 50-76% CIP was removed with 0.5-1.5 mg CIP/L in the feed, although at 4.7 mg/L its removal efficiency decreased to <20%. It was found that biological degradation was the main mechanism for removing CIP, while adsorption onto the sludge only contributed a small fraction, and an even smaller fraction was due to the waste sludge discharged. CIP was biodegraded to some degree in the AnMBR, with some intermediate compounds detected using LC-MS/MS and GC-MS. This work showed the effectiveness of an AnMBR in removing CIP at low concentrations of <1.5 mg/L, and hence may be an effective treatment for removing other antibiotics from wastewater.

Bioremoval of non-steroidal anti-inflammatory drugs by Pseudoxanthomonas sp. DIN-3 isolated from biological activated carbon process

The presence of non-steroidal anti-inflammatory drugs (NSAIDs) in the environment is an emerging concern owing to their potential threat on aquatic ecosystems and living organisms. To investigate the bioremoval potential of a biological activated carbon (BAC) filter for the removal of NSAIDs, removal of diclofenac (DCF), ibuprofen (IBU), and naproxen (NAP) by biofilms on a bench-scaled BAC column operated for 400 days was studied. The results showed that the BAC column effectively removed the three NSAIDs (>90%). One bacterial strain isolated from the BAC, Pseudoxanthomonas sp. DIN-3, was able to simultaneously remove DCF, IBU, and NAP, which were supplied as the sole carbon source. In 14 days, 23%, 41%, and 39% of DCF, IBU, and NAP (50 μg L^-1) were bioremoved, respectively, and strain DIN-3 eliminated IBU more rapidly than the other two NSAIDs. If only a single drug was added as the sole carbon source, ignoring the other drugs, the removal ability was overestimated by 5.0-27.0%. More efficient bioremoval was achieved, concomitantly with bacterial growth, via a co-metabolism with acetate, glucose, or methanol. Their intermediates were identified by UPLC-QQQ-MS, and their respective degradation pathways were also proposed. Moreover, based on the complete genome sequence of strain DIN-3, 49 related genes encoding the main enzymes involved in DCF, IBU, and NAP biodegradation were identified, including hemE, lpd, yihx, ligC, pobA, and ligA. These results suggested that Pseudoxanthomonas sp. DIN-3 is a potential degrader of DCF, IBU, and NAP, and to the best of our knowledge, this is the first report that demonstrates the bioremoval of DCF, IBU, and NAP simultaneously by an individual bacterial strain isolated from the environment. However, the bioremoval potential should be evaluated when assessing the applicability of the strain in the environment because of the combined effects of various pharmaceutical contaminants. The obtained results provide a foundation for the use of Pseudoxanthomonas sp. DIN-3 in the bioremoval of polycyclic NSAID-contaminated environments.

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 of antibiotics in three distinct sludge treatment wetlands under different operating conditions

Sludge treatment wetlands (STWs) have recently been used to treat surplus sludge. However, the distribution of antibiotics involved in the process has not been comprehensively investigated. This study aimed to evaluate the fate of two antibiotics, i.e., ciprofloxacin (CIP) and azithromycin (AZM) in STWs during the treatment of surplus sludge. Three pilot-scale STWs units-S1 with aeration tubes, S2 with aeration tubes and reed planting, and S3 with reed planting-were constructed and operated under feeding followed by resting periods. The results showed that antibiotic content in residual sludge decreased over time and unit S2 performed the best in terms of antibiotic removal. Planting reed considerably improved the antibiotic removal performance of the STWs. Biodegradation and absorption resulted in removal of most of the antibiotics in the test units. Less than 2% of the antibiotics was taken up by plants, whereas <5% of the influent antibiotics left the STW units through the drainage discharge. Overall, STW units contributed to effectively decrease CIP and AZM to 41-72% and 49-84%, respectively.

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.

Soil contamination with antibiotics in a typical peri-urban area in eastern China: Seasonal variation, risk assessment, and microbial responses

The prevalence and persistence of antibiotics in soils has become an emerging environmental issue and an increasing threat to soil security and global public health. The problem is more severe in areas undergoing rapid urbanization; however, the ecological risks of antibiotics, seasonal variability, and associated soil microbial responses in peri-urban soils have not been well-explored. The seasonal soil sampling campaigns were conducted in a typical peri-urban watershed in eastern China to investigate distribution of antibiotics. The results demonstrated higher mean concentrations of most antibiotic compounds in winter than in summer in peri-urban soils. The seasonal variations of norfloxacin, enrofloxacin, and ciprofloxacin were more significant than those of other antibiotics, due to their higher migration ability and bioavailability. An ecological risk assessment demonstrated that chlortetracycline, ciprofloxacin, doxycycline, and ofloxacin can pose high risks to soil microorganisms. Furthermore, the coexistence of multiple antibiotics obviously poses higher risks than individual compounds. A redundancy analysis demonstrated that tetracyclines mainly showed negative correlations with Firmicutes and Chloroflexi, and quinolones showed obviously negative correlations with Acidobacteria, Gemmatimonadetes, and Nitrospirae, suggesting potential inhibition from antibiotics on biological activities or biodegradation processes. However, the persistence of antibiotics in soil results in a significant decrease in bacterial diversity and a change in dominant species. Our results provide an overview of the seasonal variability of antibiotics and the associated effects on bacterial communities in peri-urban soils. The results can provide scientific guidance on decreasing soil contamination with antibiotics to enhance soil security in similar areas.

Municipal solid waste biochar-bentonite composite for the removal of antibiotic ciprofloxacin from aqueous media

This study investigates the adsorption of ciprofloxacin (CPX) onto a municipal solid waste derived biochar (MSW-BC) and a composite material developed by combining the biochar with bentonite clay. A bentonite-MSW slurry was first prepared at 1:5 ratio (w/w), and then pyrolyzed at 450 °C for 30 min. The composite was characterized by scanning electron microscopy (SEM), Powder X-ray diffraction (PXRD) and Fourier transform infrared (FTIR) spectroscopy before and after CPX adsorption. Batch experiments were conducted to assess the effect of pH, reaction time and adsorbate dosage. The SEM images confirmed successful modification of the biochar with bentonite showing plate like structures. The PXRD patterns showed changes in the crystalline lattice of both MSW-BC and the composite before and after CPX adsorption whereas the FTIR spectra indicated merging and widening of specific bands after CPX adsorption. The optimum CPX adsorption was achieved at pH 6, and the maximum adsorption capacity of the composite calculated via isotherm modeling was 190 mg/g, which was about 40% higher than the pristine MSW-BC. The Hill isotherm model along with pseudo-second order and Elovich kinetic models showed the best fit to the adsorption data. The most plausible mechanism for increased adsorption capacity is the increased active sites of the composites for CPX adsorption through induced electrostatic interactions between the functional groups of the composite and CPX molecules. The added reactive surfaces in the composite because of bentonite incorporation, and the intercalation of CPX in the clay interlayers improved the adsorption of CPX by the biochar-bentonite composite compared to the pristine biochar. Thus, MSW-BC-bentonite composites could be considered as a potential material for remediating pharmaceuticals in aqueous media.

Removal of veterinary antibiotics in constructed wetland microcosms - Response of bacterial communities

This study aimed to evaluate the response of bacteria, in terms of microbial community structure, from constructed wetland (CW) microcosms exposed to two veterinary antibiotics, enrofloxacin (ENR) and ceftiofur (CEF), alone or in a mixture, identifying which bacterial groups were dominant in CWs substrate during livestock wastewater treatment. Wastewater, not-doped or doped with ENR and/or CEF (100 µg/L each), was treated during 18 one-week cycles. Systems showed removal percentages > 85% for the added antibiotics, showing also high removal percentages for nutrients and organic matter and confirming CWs systems were working properly. However, both time of exposure and presence of antibiotics influenced significantly CWs substrate bacterial community structure. Pyrosequencing results showed bacterial communities were dominated by phyla Proteobacteria (38-48%), Firmicutes (20-27%), Bacteroidetes (12-15%) and Actinobacteria (4-9%), and that their relative abundance was clearly affected by the presence of the antibiotics. Results suggest the applicability of CWs for the removal of veterinary antibiotics from livestock wastewaters and provide new knowledge about the bacteria within the system, which can potentially be involved in removal processes. This information could in the future be used to improve CWs removal rates of pharmaceuticals from livestock wastewaters.

Biodegradation of oxytetracycline and enrofloxacin by autochthonous microbial communities from estuarine sediments

This work investigated the potential of microbial communities native to an estuarine environment to biodegrade enrofloxacin (ENR) and oxytetracycline (OXY). Sediments collected from two sites in the Douro river estuary (Porto, Portugal) were used as inocula for the biodegradation experiments. Experiments were carried out for one month, during which ENR and OXY (1 mg L^-1) were supplemented individually or in mixture to the cultures at 10-day intervals. Acetate (400 mg L^-1) was added to the cultures every 3 days to support microbial growth. A series of experimental controls were established in parallel to determine the influence of abiotic breakdown and adsorption in the removal of the antibiotics. Removal of antibiotics was followed by measuring their concentration in the culture medium. Additionally, next-generation sequencing of the 16S rRNA gene amplicon was employed to understand how microbial communities responded to the presence of the antibiotics. At the end of the biodegradation experiments, microbial cultures derived from the two estuarine sediments were able to remove up to 98% of ENR and over 95% of OXY. The mixture of antibiotics did not affect their removal. ENR was removed mainly by biodegradation, while abiotic mechanisms were found to have a higher influence in the removal of OXY. Both antibiotics adsorbed at different extents to the estuarine sediments used as inocula but exhibited a higher affinity to the sediment with finer texture and higher organic matter content. The presence of ENR and OXY in the culture media influenced the dynamics of the microbial communities, resulting in a lower microbial diversity and richness and in the predominance of bacterial species belonging to the phylum Proteobacteria. Therefore, microbial communities native from estuarine environments have potential to respond to the contamination caused by antibiotics and may be considered for the recovering of impacted environments through bioremediation.

Profiling microbial communities in a watershed undergoing intensive anthropogenic activities

In lotic ecosystems highly susceptible to anthropogenic activities, the influences of environmental variables on microbial communities and their functions remain poorly understood, despite our rapidly increasing sequencing ability. In this study, we profiled the microbial communities in the hyporheic sediments of a watershed undergoing intensive anthropogenic activities via next-generation sequencing of 16S rRNA V4-V5 hypervariable regions on Illumina MiSeq platform. Tidal impacts on microbial communities were investigated via co-occurrence networks. In addition, the influences of physicochemical variables including salinity, and the concentrations of nutrients, organic matter and heavy metals on the microbial communities were explored via canonical correspondence analyses. The sediment samples were collected from 19 sites covering the whole main river stem of the target watershed (n = 19; Maozhou river watershed, Shenzhen, China). The samples were sub-divided in the field for microbiological analyses and measurements of physicochemical variables. The results indicated that core microbiome was associated with archaea methanogens and bacteria members from Proteobacteria, Chloroflexi, Bacteroidetes, Acidobacteria, Synergistetes and Firmicutes, among which, gram-negative and anaerobic bacteria genera contributing to the cycling of carbon, nitrogen and sulfur were predominant. Site-specific microbiomes were revealed that may serve as indicators of local environmental conditions (e.g., members affiliated to Oceanospirillales were abundant at sites with salt intrusion). Distinct microbial co-occurrence networks were identified for non-tidal, inter-tidal and tidal sites. Major environmental factors influencing microbial community composition included the concentrations of nitrate and bicarbonate in river water, pore water concentrations of sulfate, dissolved organic carbon and electrical conductivity, as well as manganese concentrations associated with the solid sediment. Collectively, the results of this study provide fundamental insights into the influence of environmental perturbations on microbial community composition in a lotic system, which may aid in the design of effective remediation and/or restoration strategies in the target watershed and beyond.

Distribution, dynamics and determinants of antibiotics in soils in a peri-urban area of Yangtze River Delta, Eastern China

Antibiotics are increasingly recognized as anthropogenic contaminants in soils, and they can persist through a complex vicious cycle of transformation and bioaccumulation. In this study, we quantified 11 quinolones (QNs), 5 sulfonamides (SAs), 5 macrolides (MLs), and 4 tetracyclines (TCs) in soils at three soil layers (0-10, 10-20, 20-40 cm) in a typical peri-urban catchment in the Yangtze River Delta, Eastern China. The results showed that total antibiotic levels were significantly higher in cropland topsoil (p < 0.05) compared to orchards and forests (p < 0.05). Moreover, a significant seasonal variation for antibiotic concentrations in croplands' topsoil were observed in the summer (50.59 ± 84.55 ng/g) and winter (112.44 ± 140.58 ng/g). Chlortetracycline (15.30 ± 45.44 ng/g), enrofloxacin (0.43 ± 0.93 ng/g), sulfamethazine (0.05 ± 0.02 ng/g) and clarithromycin (0.03 ± 0.03 ng/g) were detected with the highest frequencies within TCs, QNs, SAs, and MLs, respectively. Concentrations of TCs, QNs, and SAs decreased with increasing soil depth. The concentrations of TCs, QNs, and SAs were significantly affected by the intensity of human activities. According to the results of redundancy analysis (RDA), anthropogenic effects on the distribution of antibiotics in soils in winter were so strong that they dwarfed the effects of environmental factors. In summer, human activities and their interactions with environmental factors were the dominant contributors to variations in soil antibiotics. In addition, the results of RDA suggested that soil pH and organic matter closely correlated with the levels of antibiotics, and Actinobacteria was the predominant contributor to the biodegradation of antibiotics in this study area.

Study of ciprofloxacin removal by biochar obtained from used tea leaves

In this study, used tea leaves (UTLs) were pyrolyzed to obtain used tea-leaf biochar (UTC), and then the UTC was used as an adsorbent to remove ciprofloxacin (CIP) from aqueous solutions. Batch experiments were conducted to investigate the CIP adsorption performance and mechanism. The results showed that the CIP-adsorbing ability first increased and then declined as the UTC pyrolysis temperature increased. The UTC obtained at 450°C presented excellent CIP-absorbing ability at pH6 and 40°C. The maximum monolayer adsorption capacity was 238.10mg/g based on the Langmuir isotherm model. The pseudo-second-order kinetic equation agreed well with the CIP adsorption process, which was controlled by both external boundary layer diffusion and intra-particle diffusion. The characterization analysis revealed that the OH groups, CC bonds of aromatic rings, CH groups in aromatic rings and phenolic CO bonds play vital roles in the CIP adsorption process, and that the NC, NO, OCO and COH groups of UTC were consumed in large quantities. π-π interactions, hydrogen bonding and electrostatic attraction are inferred as the main adsorption mechanisms. The present work provides not only a feasible and promising approach for UTLs utilization but also a potential adsorbent material for removing high concentrations of CIP from aqueous solutions.

Aerobic biotransformation of the antibiotic ciprofloxacin by Bradyrhizobium sp. isolated from activated sludge

Ciprofloxacin (CIP) is an antibiotic that is widely used to treat bacterial infections and is poorly biodegraded during wastewater treatment. In this study, a CIP-degrading bacterial strain (GLC_01) was successfully retrieved from activated sludge by enrichment and isolation. The obtained bacterial strain shares over 99% nucleotide identity of the 16S rRNA gene with Bradyrhizobium spp. Results show that Bradyrhizobium sp. GLC_01 degraded CIP via cometabolism with another carbon substrate following a first-order kinetics degradation reaction. CIP degradation by Bradyrhizobium sp. GLC_01 increased when the concentration of the primary carbon source increased. The biodegradability of the primary carbon source also affected CIP degradation. The use of glucose and sodium acetate (i.e. readily biodegradable), respectively, as a primary carbon source enhanced CIP biotransformation, compared to starch (i.e. relatively slowly biodegradable). CIP degradation decreased with the increase of the initial CIP concentration. Over 70% CIP biotransformation was achieved at 0.05 mg L^-1 whereas CIP degradation decreased to 26% at 10 mg L^-1. The phylogenetic identification and experimental verification of this CIP-degrading bacterium can lead to a bioengineering approach to manage antibiotics and possibly other persistent organic contaminants during wastewater treatment.

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.

Effect of ciprofloxacin on methane production and anaerobic microbial community

This study investigated the effects and fate of CIP on anaerobic sludge over a wide range of concentrations (0.05-50 mg/L), and 0.5-50 mg/L significantly inhibited organic removal and methanogenic activity, increased volatile fatty acids accumulation and low molecular weight soluble microbial products (SMPs), including p-cresol and nitrogen-containing compounds. Although microbial communities exposed to CIP did not differ significantly from the control in species diversity indices, Syntrophobacter and Methanothrix associated with acetogenesis and acetoclastic methanogenesis, respectively, were underrepresented in the CIP-exposed communities. Our study advances understanding of how environmentally relevant concentrations of CIP disrupts anaerobic digestion, which has important implications for anaerobic engineered systems treating CIP-bearing waste streams.

Prevalence of quinolone resistance genes, copper resistance genes, and the bacterial communities in a soil-ryegrass system co-polluted with copper and ciprofloxacin

The presence of high concentrations of residual antibiotics and antibiotic resistance genes (ARGs) in soil may pose potential health and environmental risks. This study investigated the prevalence of plasmid-mediated quinolone resistance (PMQR) genes, copper resistance genes (CRGs), and the bacterial communities in a soil-ryegrass pot system co-polluted with copper and ciprofloxacin (CIP; 0, 20, or 80 mg kg^-1 dry soil). Compared with the samples on day 0, the total relative abundances of the PMQR genes and mobile genetic elements (MGEs) were reduced significantly by 80-89% in the ryegrass and soil by the cutting stage (after 75 days). The abundances of PMQR genes and MGEs were reduced by 63-81% in soil treated with 20 mg kg^-1 CIP compared with the other treatments, but the abundances of CRGs increased by 18-42%. The presence of 80 mg kg^-1 CIP affected the microbial community structure in the soil by increasing the abundances of Acidobacteria and Thaumarchaeota, but decreasing those of Firmicutes. Redundancy analysis indicated that the pH and microbial composition were the main factors that affected the variations in PMQR genes, MGEs, and CRGs, where they could explain 42.2% and 33.3% of the variation, respectively. Furthermore, intI2 may play an important role in the transfer of ARGs. We found that 80 mg kg^-1 CIP could increase the abundances of ARGs and CRGs in a soil-ryegrass pot system.

Simultaneous removal of ciprofloxacin, norfloxacin, sulfamethoxazole by co-producing oxidative enzymes system of Phanerochaete chrysosporium and Pycnoporus sanguineus

Pycnoporus sanguineus could remove 98.5% ciprofloxacin (CIP), 96.4% norfloxacin (NOR), 100% sulfamethoxazole (SMX), and 100% their mixture through biotransformation within 2 d, while Phanerochaete chrysosporium could only remove 64.5% CIP, 73.2% NOR, and 63.3% SMX through biosorption and biotransformation within 8 d, respectively. The efficiencies of antibiotic bioremoval under co-culture were more than that under the pure culture of P. chrysosporium but less than that under the pure culture of P. sanguineus. However, only 2% CIP and 3% NOR under co-culture were detected in the mycelia. In vitro enzymatic degradation and in vivo cytochrome P450 inhibition experiments revealed that laccase and cytochrome P450 could play roles in the removal of above all antibiotics, while manganese peroxidase could only play role in SMX removal. Transformation products of CIP and NOR under the pure culture of P. chrysosporium could be assigned to three different reaction pathways: (i) defluorination or dehydration, (ii) decarboxylation, and (iii) oxidation of the piperazinyl substituent. Additionally, other pathways, (iv) monohydroxylation, and (v) demethylation or deethylation at position N₁ also occurred under the co-culture and pure culture of P. sanguineus. Antibacterial activity of antibiotics could be eliminated after treatments with pure and co-culture of P. chrysosporium and P. sanguineus. The cytotoxicity of the metabolites of SMX and NOR under co-culture was lower than that under the pure culture of P. sanguineus, indicating co-culture is a more environmentally friendly strategy to eliminate SMX and NOR.

Riboswitching with ciprofloxacin-development and characterization of a novel RNA regulator

RNA molecules play important and diverse regulatory roles in the cell. Inspired by this natural versatility, RNA devices are increasingly important for many synthetic biology applications, e.g. optimizing engineered metabolic pathways, gene therapeutics or building up complex logical units. A major advantage of RNA is the possibility of de novo design of RNA-based sensing domains via an in vitro selection process (SELEX). Here, we describe development of a novel ciprofloxacin-responsive riboswitch by in vitro selection and next-generation sequencing-guided cellular screening. The riboswitch recognizes the small molecule drug ciprofloxacin with a KD in the low nanomolar range and adopts a pseudoknot fold stabilized by ligand binding. It efficiently interferes with gene expression both in lower and higher eukaryotes. By controlling an auxotrophy marker and a resistance gene, respectively, we demonstrate efficient, scalable and programmable control of cellular survival in yeast. The applied strategy for the development of the ciprofloxacin riboswitch is easily transferrable to any small molecule target of choice and will thus broaden the spectrum of RNA regulators considerably.

Study of ciprofloxacin biodegradation by a Thermus sp. isolated from pharmaceutical sludge

Ciprofloxacin (CIP) is an antibiotic drug frequently detected in manure compost and is difficult to decompose at high temperatures, resulting in a potential threat to the environment. Microbial degradation is an effective and environmentally friendly method to degrade CIP. In this study, a thermophilic bacterium that can degrade CIP was isolated from sludge sampled from an antibiotics pharmaceutical factory. This strain is closely related to Thermus thermophilus based on 16S rRNA gene sequence analysis and is designated C419. The optimal temperature and pH values for CIP degradation are 70°C and 6.5, respectively, and an appropriate sodium acetate concentration promotes CIP degradation. Seven major biodegradation metabolites were identified by an ultra-performance liquid chromatography tandem mass spectrometry analysis. In addition, strain C419 degraded other fluoroquinolones, including ofloxacin, norfloxacin and enrofloxacin. The supernatant from the C419 culture grown in fluoroquinolone-containing media showed attenuated antibacterial activity. These results indicate that strain C419 might be a new auxiliary bacterial resource for the biodegradation of fluoroquinolone residue in thermal environments.

Dissipation of antibiotics in three different agricultural soils after repeated application of biosolids

Application of biosolids to agricultural soils is one of the pathways by which antibiotics can be introduced into agricultural ecosystems. A pot experiment was conducted with repeated soil amendment with biosolids to examine the concentrations of four classes of antibiotics (tetracyclines, sulfonamides, fluoroquinolones, and macrolides) and their dissipation in three different soil types in wheat-rice rotations. Antibiotics accumulate in the soils after repeated application of biosolids. Fluoroquinolones showed stronger accumulation and persistence in the test soils than the other three classes of antibiotics. The maximum residual antibiotic concentration was that of norfloxacin at 155 ± 16 μg kg^-1 in the Typic Hapli-Stagnic Anthrosols (paddy soil). Predicted half-lives were up to 3.69 years, a much longer period than that between biosolid applications (twice each year on average). Antibiotic accumulation followed the rough order fluoroquinolones > tetracyclines > macrolides > sulfonamides, and the sulfonamides were seldom encountered. When biosolid application was suspended, the dissipation rate accelerated. Antibiotic dissipation was slightly slower when biosolids with high heavy metal concentrations were applied and microbial degradation may have been the main mechanism of dissipation. Norfloxacin persistence was positively correlated with its soil adsorption capacity. Cation exchange capacity and soil organic matter content may have vital roles in the soil adsorption of fluoroquinolones. Because of their persistence, the fluoroquinolones must be taken into account in the planning of biosolid applications in agricultural practice.

Fate of sulfamethoxazole, its main metabolite N-ac-sulfamethoxazole and ciprofloxacin in agricultural soils amended or not by organic waste products

Spreading organic waste products (OWP) issued from sewage sludge or manures into soil may disseminate antibiotics with unknown risks for human health and environment. Our objectives were to compare the fate of two sulfonamides, sulfamethoxazole (SMX) and its metabolite N-acetyl-sulfamethoxazole (N-ac-SMX), and one fluoroquinolone, ciprofloxacin (CIP), in an unamended soil, and two soils regularly amended since 1998 with a sewage sludge and green waste compost and with farmyard manure respectively. Incubations of soil spiked with ¹⁴C labelled SMX or N-ac-SMX (0.02 mg kg^-1) or CIP (0.15 mg kg^-1) allowed a quantification of radiolabeled molecules in the mineralized, easily, hardly and non-extractable fractions after 3 and 156 days. Nature of ¹⁴C molecules was also analyzed by HPLC in extractable fractions after 3 and 156 days. SMX and N-ac-SMX dissipation was fast and due to i) mineralization (∼10% of recovered ¹⁴C after 156 days) or incomplete degradation (production of metabolites), ii) adsorption, even if both sulfonamides present low Kd (<3 L kg^-1) and iii) formation of non-extractable residues (NER), representing more than 50% of recovered radioactivity. N-ac-SMX was more mineralized than SMX, and formed more progressively NER, after a step of deacetylation. Adsorption of CIP was fast and formed mainly NER (>72%) whereas its mineralization was negligible. Repeated applications of OWP tend to enhance adsorption of antibiotics and lower their degradation, through the quantity and quality of the built up soil organic matter. If applications of sewage sludge compost favor adsorption and inhibit mineralization, applications of manure boost the formation of non-extractable residues.

Statistically optimized ceftriaxone sodium biotransformation through Achromobacter xylosoxidans strain Cef6: an unusual insight for bioremediation

The present study underlines a unique promising approach toward efficient biotransformation of ceftriaxone sodium (Ceftx), a highly frequent prescribed cephalosporin antibiotic, by a newly bacterium namely Achromobacter xylosoxidans strain Cef6 isolated from Ceftx contaminated raw materials in pharmaceutical industries. A three step sequential statistical-mathematical approach (Plackett-Burman design [PBD], Central Composite Design [CCD], and ridge-canonical analyses) was anticipated to optimize the biotransformation process. Ceftx concentration and medium volume: bottle volume ratio, two key determinants, significantly (p < 0.05) affected the process outcome deduced by regression analysis of PBD' data. CCD and ridge-canonical analyses localized the optimal levels of Ceftx concentration and medium volume: 250 ml bottle volume ratio to be 0.39 and 7.973 g Ceftx/L modified tryptic soy broth achieving Ceftx biotransformation (100%) after 39 h under aerobic static conditions at 30 °C, irrespectively deduced via HPLC analysis. Impressively, only one of five Ceftx byproducts was detected by the end of the biotransformation process. To the best of authors' knowledge, this is the first report addressing a detailed study regarding efficient biotransformation of Ceftx by single bacterium not bacterial consortium under aerobic conditions. Present data would greatly encourage applying this approach for decontamination of some Ceftx contaminated environmental sites.