Biotransformation of flumequine by the fungus Cunninghamella elegans

Reduction of metronidazole in municipal wastewater and protection of activated sludge system using a novel immobilized Aspergillus tabacinus LZ-M

Metronidazole (MNZ) accumulation inhibits municipal wastewater treatment bio-systems, and an effective solution to augment anaerobic activated sludge (AAS) is required. This research discovered that Aspergillus tabacinus LZ-M could degrade 77.39% of MNZ at 5 mg/L. MNZ was metabolized into urea, and the enzymes involved in its degradation were aminotransferase, methyltransferase, monooxygenase, and CN cleavage hydrolase. The strain was immobilized in polyurethane foam and used in AAS for the treatment of MNZ-containing municipal wastewater. The results showed that, using immobilized LZ-M, MNZ was completely removed, and the degradation efficiency of wastewater's chemical oxygen demand (COD) was increased from 11.7% to 83.31%. The extracellular polymer and ROS levels indicated that MNZ's toxicity on AAS was reduced. Furthermore, bioaugmentation stabilized its microbial community, and decreased MNZ resistance genes. These observations confirm that the immobilized fungi are effective in protecting AAS against antibiotic contamination in the treatment process of municipal wastewater.

Enantioselective Behavior of Flumequine Enantiomers and Metabolites' Identification in Sediment

The enantioselective adsorption, degradation, and transformation of flumequine (FLU) enantiomers in sediment were investigated to elucidate the enantioselective environmental behaviors. The results of adsorption test showed that stereoselective differences of FLU enantiomers in sediment samples and the adsorbing capacity of S-(-)-FLU and R-(+)-FLU are higher than the racemate, and the pH values of the sediment determined the adsorption capacity. Enantioselective degradation behaviors were found under nonsterilized conditions and followed pseudo-first-order kinetic. The R-(+)-FLU was preferentially degraded, and there was significant enantioselectivity of the degradation of FLU. It can be concluded that the microorganism was the main reason for the stereoselective degradation in sediments. The physicochemical property of sediments, such as pH value and organic matter content, can affect the degradation rate of FLU. In addition, the process of transformation of FLU enantiomers in water-sediment system had enantioselective behavior, and R-(+)-FLU was preferential transformed. Meanwhile, the main metabolites of FLU in the sediment were decarboxylate and dihydroxylation products. This study contributes the evidence of comprehensively assessing the fate and risk of chiral FLU antibiotic and enantioselective behavior in the environment.

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.

From Laboratory Tests to the Ecoremedial System: The Importance of Microorganisms in the Recovery of PPCPs-Disturbed Ecosystems

The presence of a wide variety of emerging pollutants in natural water resources is an important global water quality challenge. Pharmaceuticals and personal care products (PPCPs) are known as emerging contaminants, widely used by modern society. This objective ensures availability and sustainable management of water and sanitation for all, according to the 2030 Agenda. Wastewater treatment plants (WWTP) do not always mitigate the presence of these emerging contaminants in effluents discharged into the environment, although the removal efficiency of WWTP varies based on the techniques used. This main subject is framed within a broader environmental paradigm, such as the transition to a circular economy. The research and innovation within the WWTP will play a key role in improving the water resource management and its surrounding industrial and natural ecosystems. Even though bioremediation is a green technology, its integration into the bio-economy strategy, which improves the quality of the environment, is surprisingly rare if we compare to other corrective techniques (physical and chemical). This work carries out a bibliographic review, since the beginning of the 21st century, on the biological remediation of some PPCPs, focusing on organisms (or their by-products) used at the scale of laboratory or scale-up. PPCPs have been selected on the basics of their occurrence in water resources. The data reveal that, despite the advantages that are associated with bioremediation, it is not the first option in the case of the recovery of systems contaminated with PPCPs. The results also show that fungi and bacteria are the most frequently studied microorganisms, with the latter being more easily implanted in complex biotechnological systems (78% of bacterial manuscripts vs. 40% fungi). A total of 52 works has been published while using microalgae and only in 7% of them, these organisms were used on a large scale. Special emphasis is made on the advantages that are provided by biotechnological systems in series, as well as on the need for eco-toxicological control that is associated with any process of recovery of contaminated systems.

Oxidation of flumequine in aqueous solution by UV-activated peroxymonosulfate: Kinetics, water matrix effects, degradation products and reaction pathways

The degradation of flumequine (FLU) in aqueous solution by ultraviolet (UV)-activated peroxymonosulfate (PMS) was investigated in this work. Under the conditions of [PMS]₀:[FLU]₀ = 1:1, T = 25 ± 2 °C, pH = 7.0 ± 0.1, nearly complete removal of FLU was achieved after 60 min. The effects of various operating parameters, including oxidant doses, pH, the presence of typical ions (NH₄⁺、Mg²⁺、Fe³⁺、Cl^-、NO₃^-、HCO₃^-) and humic acid were evaluated. It was found that the pseudo-first-order rate constants of FLU degradation increased with increasing PMS dosage and decreasing solution pH. The presence of Mg²⁺ could accelerate FLU removal, while Fe³⁺, HCO₃^-, NO₃^- and HA inhibited the reaction. Moreover, the degradation of FLU in different water matrices were also explored, and the removal followed the order of Tap water > Ultrapure water > River water > Secondary clarifier effluent. According to the control and radical quenching experiment results, direct photolysis and reactive radicals (SO₄^- and HO) contributed mainly to FLU degradation in the UV/PMS system. Initial FLU molecule underwent reactions such as hydroxylation, hydroxyl substitution, demethylation, decarboxylation/decarbonylation and ring opening, leading to the formation of nineteen oxidation products. The effective degradation by UV/PMS suggests a feasible technology for treating FLU in waters and wastewaters.

Biotransformation of ciprofloxacin by Xylaria longipes: structure elucidation and residual antibacterial activity of metabolites

The impressive ability of the fungus Xylaria longipes to transform the highly persistent fluoroquinolone ciprofloxacin into microbiologically less active degradation products was demonstrated. Fluoroquinolones are used extensively in both human and veterinary medicine. Poor metabolization and high chemical stability of these synthetic antibiotics led to their presence in several environmental compartments. This undesirable behavior may promote the spread of resistance mechanisms due to concomitant exposure to bacteria. Therefore, the biotransformation of ciprofloxacin, one of the most prescribed fluoroquinolones in human medicine, by the ascomycetous soft rot fungus X. longipes was investigated in detail. Submerged cultivation of the fungus allowed for high-yield formation of four biotransformation products. These compounds were subsequently purified by preparative high-performance liquid chromatography. Applying accurate mass spectrometry and nuclear magnetic resonance spectroscopy, desethylene-ciprofloxacin, desethylene-N-acetyl-ciprofloxacin, N-formyl-ciprofloxacin and N-acetyl-ciprofloxacin were unambiguously identified. N-acetylation and N-formylation of the drug led to a 75-88% reduction of the initial antibacterial activity, whereas a breakdown of the piperazine substituent resulted in almost inactive products. These findings suggest an important role in the inactivation and degradation of this and other synthetic compounds in the environment.

Elimination of Isoxazolyl-Penicillins antibiotics in waters by the ligninolytic native Colombian strain Leptosphaerulina sp. considerations on biodegradation process and antimicrobial activity removal

In this work, Leptosphaerulina sp. (a Colombian native fungus) significantly removed three Isoxazolyl-Penicillin antibiotics (IP): oxacillin (OXA, 16000 μg L^-1), cloxacillin (CLX, 17500 μg L^-1) and dicloxacillin (DCX, 19000 μg L^-1) from water. The biological treatment was performed at pH 5.6, 28 °C, and 160 rpm for 15 days. The biotransformation process and lack of toxicity of the final solutions (antibacterial activity (AA) and cytotoxicity) were tested. The role of enzymes in IP removal was analysed through in vitro studies with enzymatic extracts (crude and pre-purified) from Leptosphaerulina sp., commercial enzymes and enzymatic inhibitors. Furthermore, the applicability of mycoremediation process to a complex matrix (simulated hospital wastewater) was evaluated. IP were considerably abated by the fungus, OXA was the fastest degraded (day 6), followed by CLX (day 7) and DCX (day 8). Antibiotics biodegradation was associated to laccase and versatile peroxidase action. Assays using commercial enzymes (i.e. laccase from Trametes versicolor and horseradish peroxidase) and inhibitors (EDTA, NaCl, sodium acetate, manganese (II) ions) confirmed the significant role of enzymatic transformation. Whereas, biomass sorption was not an important process in the antibiotics elimination. Evaluation of AA against Staphylococcus aureus ATCC 6538 revealed that Leptosphaerulina sp. also eliminated the AA. In addition, the cytotoxicity assay (MTT) on the HepG2 cell line demonstrated that the IP final solutions were non-toxic. Finally, Leptosphaerulina sp. eliminated OXA and its AA from synthetic hospital wastewater at 6 days. All these results evidenced the potential of Leptosphaerulina sp. mycoremediation as a novel environmentally friendly process for the removal of IP from aqueous systems.

Biotransformation of 4-fluoro-N-(1-{2-[(propan-2-yl)phenoxy]ethyl}-8-azabicyclo[3.2.1]octan-3-yl)-benzenesulfonamide, a novel potent 5-HT7 receptor antagonist with antidepressant-like and anxiolytic properties: In vitro and in silico approach

The aim of the study was to investigate the metabolism of 4-fluoro-N-(1-{2-[(propan-2-yl)phenoxy]ethyl}-8-azabicyclo[3.2.1]octan-3-yl)-benzenesulfonamide (PZ-1150), a novel 5-HT₇ receptor antagonist with antidepressant-like and anxiolytic properties, by the following three ways: in vitro with microsomes; in vitro employing Cunninghamella echinulata, and in silico using MetaSite. Biotransformation of PZ-1150 with microsomes resulted in five metabolites, while transformation with C. echinulata afforded two metabolites. In both models, the predominant metabolite occurred due to hydroxylation of benzene ring. In silico data coincide with in vitro experiments, as three MetaSite metabolites matched compounds identified in microsomal samples. In human liver microsomes PZ-1150 exhibited in vitro half-life of 64 min, with microsomal intrinsic clearance of 54.1 μL/min/mg and intrinsic clearance of 48.7 mL/min/kg. Therefore, PZ-1150 is predicted to be a high-clearance agent. The study demonstrated the applicability of using microsomal model coupled with microbial model to elucidate the metabolic pathways of compounds and comparison with in silico metabolite predictions.

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.

Metabolism of an Insecticide Fenitrothion by Cunninghamella elegans ATCC36112

In this study, the detailed metabolic pathways of fenitrothion (FNT), an organophosphorus insecticide by Cunninghamella elegans, were investigated. Approximately 81% of FNT was degraded within 5 days after treatment with concomitant accumulation of four metabolites (M1-M4). The four metabolites were separated by high-performance liquid chromatography, and their structures were identified by mass spectroscopy and/or nuclear magnetic resonance. M3 is confirmed to be an initial precursor of others and identified as fenitrothion-oxon. On the basis of their metabolic profiling, the possible metabolic pathways involved in phase I and II metabolism of FNT by C. elegans was proposed. We also found that C. elegans was able to efficiently and rapidly degrade other organophosphorus pesticides (OPs). Thus, these results will provide insight into understanding of the fungal degradation of FNT and the potential application for bioremediation of OPs. Furthermore, the ability of C. elegans to mimic mammalian metabolism would help us elucidate the metabolic fates of organic compounds occurring in mammalian liver cells and evaluate their toxicity and potential adverse effects.

Overview on the Biochemical Potential of Filamentous Fungi to Degrade Pharmaceutical Compounds

Pharmaceuticals represent an immense business with increased demand due to intensive livestock raising and an aging human population, which guarantee the quality of human life and well-being. However, the development of removal technologies for these compounds is not keeping pace with the swift increase in their use. Pharmaceuticals constitute a potential risk group of multiclass chemicals of increasing concern since they are extremely frequent in all environments and have started to exhibit negative effects on micro- and macro-fauna as well as on human health. In this context, fungi are known to be extremely diverse and poorly studied microorganisms despite being well suited for bioremediation processes, taking into account their metabolic and physiological characteristics for the transformation of even highly toxic xenobiotic compounds. Increasing studies indicate that fungi can transform many structures of pharmaceutical compounds, including anti-inflammatories, β-blockers, and antibiotics. This is possible due to different mechanisms in combination with the extracellular and intracellular enzymes, which have broad of biotechnological applications. Thus, fungi and their enzymes could represent a promising tool to deal with this environmental problem. Here, we review the studies performed on pharmaceutical compounds biodegradation by the great diversity of these eukaryotes. We examine the state of the art of the current application of the Basidiomycota division, best known in this field, as well as the assembly of novel biodegradation pathways within the Ascomycota division and the Mucoromycotina subdivision from the standpoint of shared enzymatic systems, particularly for the cytochrome P450 superfamily of enzymes, which appear to be the key enzymes in these catabolic processes. Finally, we discuss the latest advances in the field of genetic engineering for their further application.

Degradation of fluoroquinolone antibiotics by ferrate(VI): Effects of water constituents and oxidized products

The degradation of five fluoroquinolone (FQ) antibiotics (flumequine (FLU), enrofloxacin (ENR), norfloxacin (NOR), ofloxacin (OFL) and marbofloxacin (MAR)) by ferrate(VI) (Fe(VI)O4(2-), Fe(VI)) was examined to demonstrate the potential of this iron-based chemical oxidant to treat antibiotics in water. Experiments were conducted at different molar ratios of Fe(VI) to FQs at pH 7.0. All FQs, except FLU, were degraded within 2 min at [Fe(VI)]:[FQ] ≤ 20.0. Multiple additions of Fe(VI) improved the degradation efficiency, and provided greater degradation than a single addition of Fe(VI). The effects of anions, cations, and humic acid (HA), usually present in source waters and wastewaters, on the removal of FLU were investigated. Anions (Cl(-), SO4(2-), NO3(-), and HCO3(-)) and monovalent cations (Na(+) and K(+)) had no influence on the removal of FLU. However, multivalent cations (Ca(2+), Mg(2+), Cu(2+), and Fe(3+)) in water decreased the efficiency of FLU removal by Fe(VI). An increase in the ionic strength of the solution, and the presence of HA in the water, also decreased the percentage of FLU removed by Fe(VI). Experiments on the removal of selected FQs, present as co-existing antibiotics in pure water, river water, synthetic water and wastewater, were also conducted to demonstrate the practical application of Fe(VI) to remove the antibiotics during water treatment. The seventeen oxidized products (OPs) of FLU were identified using solid phase extraction-liquid chromatography-high-resolution mass spectrometry. The reaction pathways are proposed, and are theoretically confirmed by molecular orbital calculations.

Validation of a Chiral Liquid Chromatographic Method for the Degradation Behavior of Flumequine Enantiomers in Mariculture Pond Water

In this work, flumequine (FLU) enantiomers were separated using a Chiralpak OD-H column, with n-hexane-ethanol (20:80, v/v) as the mobile phase at a flow rate of 0.6 mL/min. Solid phase extraction (SPE) was used for cleanup and enrichment. The limit of detection, limit of quantitation, linearity, precision, and intra/interday variation of the chiral high-performance liquid chromatography (HPLC) method were determined. The developed method was then applied to investigate the degradation behavior of FLU enantiomers in mariculture pond water samples. The results showed that the degradation of FLU enantiomers under natural, sterile, or dark conditions was not enantioselective. Chirality 28:649-655, 2016. © 2016 Wiley Periodicals, Inc.

Marine fungi isolated from Chilean fjord sediments can degrade oxytetracycline

Salmon farming is the main economic activity in the fjords area of Southern Chile. This activity requires the use of antibiotics, such as oxytetracycline, for the control and prevention of diseases, which have a negative impact on the environment. We analyzed the abilities of endemic marine fungi to biodegrade oxytetracycline, an antibiotic used extensively in fish farming. We isolated marine fungi strains from sediment samples obtained from an area of fish farming activity. The five isolated strains showed an activity on oxytetracycline and were identified as Trichoderma harzianum, Trichoderma deliquescens, Penicillium crustosum, Rhodotorula mucilaginosa, and Talaromyces atroroseus by a scanning electron microscopy and characterized by molecular techniques. Results showed significant degradation in the concentration of oxytetracycline at the first 2 days of treatment for all strains analyzed. At 21 days of treatment, the concentration of oxytetracycline was decreased 92 % by T. harzianum, 85 % by T. deliquescens, 83 % by P. crustosum, 73 % by R. mucilaginosa, and 72 % by T. atroroseus, all of which were significantly higher than the controls. Given these results, we propose that fungal strains isolated from marine sediments may be useful tools for biodegradation of antibiotics, such as oxytetracycline, in the salmon industry.

Microbial degradation of fluorinated drugs: biochemical pathways, impacts on the environment and potential applications

Since the discovery over 60 years ago of fluorocortisone's biological properties (9-α-Fluoro derivatives of cortisone and hydrocortisone; Fried J and Sabo EF, J Am Chem Soc 76: 1455-1456, 1954), the number of fluorinated drugs has steadily increased. With the improvement in synthetic methodologies, this trend is likely to continue and will lead to the introduction of new fluorinated substituents into pharmaceutical compounds. Although the biotransformation of organofluorine compounds by microorganisms has been well studied, specific investigations on fluorinated drugs are relatively few, despite the increase in the number and variety of fluorinated drugs that are available. The strength of the carbon-fluorine bond conveys stability to fluorinated drugs; thus, they are likely to be recalcitrant in the environment or may be partially metabolized to a more toxic metabolite. This review examines the research done on microbial biotransformation and biodegradation of fluorinated drugs and highlights the importance of understanding how microorganisms interact with this class of compound from environmental, clinical and biotechnological perspectives.

Fast removal of the antibiotic flumequine from aqueous solution by ozonation: Influencing factors, reaction pathways, and toxicity evaluation

As one of the first generation of fluoroquinolone antibiotics, flumequine (FLU) has been detected ubiquitously in surface waters and municipal wastewaters. In light of FLU's possible adverse effects on aquatic species, the removal of this antibiotic has received worldwide attention. In this study, the kinetics, transformation products, mechanisms and toxicity variations of the ozonation process for FLU were systematically determined. The possible effects of solution pH, addition of inorganic ions, dissolved organic matter, and tert-butyl-alcohol (a radical scavenger), as well as the type of water matrices on FLU removal by ozonation, were studied from the perspective of the degradation kinetics. The data obtained suggested that ozone can be used as an effective oxidant for the fast removal of FLU from natural waters. Using liquid chromatography-mass spectrometry, a total of thirteen transformation products of FLU during ozonation were identified, and their specific reaction mechanisms were also proposed. The degradation pathways involving the hydroxylation, decarboxylation and defluorination were tentatively proposed. Meanwhile, the generation of three low-molecular-weight carboxylic acids was also observed. In addition, the potential toxicity of the transformation mixtures of FLU by ozone was evaluated. Overall, this paper can be a unique contribution to the systematic elucidation of the ozonation process of this antibiotic in water.

Degradation of flumequine in aqueous solution by persulfate activated with common methods and polyhydroquinone-coated magnetite/multi-walled carbon nanotubes catalysts

In recent years, flumequine (FLU) has been ubiquitously detected in surface waters and municipal wastewaters. In light of its potential negative impacts to aquatic species, growing concern has been arisen for the removal of this antibiotic from natural waters. In this study, the kinetics, degradation mechanisms and pathways of aqueous FLU by persulfate (PS) oxidation were systematically determined. Three common activation methods, including heat, Fe(2+) and Cu(2+), and a novel heterogeneous catalyst, namely, polyhydroquinone-coated magnetite/multi-walled carbon nanotubes (Fe3O4/MWCNTs/PHQ), were investigated to activate PS for FLU removal. It was found that these three common activators enhanced FLU degradation obviously, while several influencing factors, such as solution pH, inorganic ions (especially HCO3(-) at 5 mmol/L) and dissolved organic matter extracts, exerted their different effects on FLU removal. The catalysts were characterized, and an efficient catalytic degradation performance, high stability and excellent reusability were observed. The measured total organic carbon levels suggested that FLU can be effectively mineralized by using the catalysts. Radical mechanism was studied by combination of the quenching tests and electron paramagnetic resonance analysis. It was assumed that sulfate radicals predominated in the activation of PS with Fe3O4/MWCNTs/PHQ for FLU removal, while hydroxyl radicals also contributed to the catalytic oxidation process. In addition, a total of fifteen reaction intermediates of FLU were identified, from which two possible pathways were proposed involving hydroxylation, decarbonylation and ring opening. Overall, this study represented a systematical evaluation regarding the transformation process of FLU by PS, and showed that the heterogeneous catalysts can efficiently activate PS for FLU removal from the water environment.

Biotransformation of fluoroquinolone antibiotics by ligninolytic fungi--Metabolites, enzymes and residual antibacterial activity

A group of white rot fungi (Irpex lacteus, Panus tigrinus, Dichomitus squalens, Trametes versicolor and Pleurotus ostreatus) was investigated for the biodegradation of norfloxacin (NOR), ofloxacin (OF) and ciprofloxacin (CIP). The selected fluoroquinolones were readily degraded almost completely by I. lacteus and T. versicolor within 10 and 14 d of incubation in liquid medium, respectively. The biodegradation products were identified by liquid chromatography-mass spectrometry. The analyses indicated that the fungi use similar mechanisms to degrade structurally related antibiotics. The piperazine ring of the molecules is preferably attacked via either substitution or/and decomposition. In addition to the degradation efficiency, attention was devoted to the residual antibiotic activities estimated using Gram-positive and Gram-negative bacteria. Only I. lacteus was able to remove the antibiotic activity during the course of the degradation of NOR and OF. The product-effect correlations evaluated by Principal Component Analysis (PCA) enabled elucidation of the participation of the individual metabolites in the residual antibacterial activity. Most of the metabolites correlated with the antibacterial activity, explaining the rather high residual activity remaining after the biodegradation. PCA of ligninolytic enzyme activities indicated that manganese peroxidase might participate in the degradation.

Production of drug metabolites by immobilised Cunninghamella elegans: from screening to scale up

Cunninghamella elegans is a fungus that has been used extensively as a microbial model of mammalian drug metabolism, whilst its potential as a biocatalyst for the preparative production of human drug metabolites has been often proposed, little effort has been made to enable this. Here, we describe a workflow for the application of C. elegans for the production of drug metabolites, starting from well-plate screening assays leading to the preparative production of drug metabolites using fungus immobilised either in alginate or as a biofilm. Using 12- and 96-well plates, the simultaneous screening of several drug biotransformations was achieved. To scale up the biotransformation, both modes of immobilisation enabled semi-continuous production of hydroxylated drug metabolites through repeated addition of drug and rejuvenation of the fungus. It was possible to improve the productivity in the biofilm culture for the production of 4'-hydroxydiclofenac from 1 mg/l h to over 4 mg/l h by reducing the incubation time for biotransformation and the number of rejuvenation steps.

Biotransformation of the antibiotic agent flumequine by ligninolytic fungi and residual antibacterial activity of the transformation mixtures

Flumequine, a fluoroquinolone antibiotic, is applied preferably in veterinary medicine, for stock breeding and treatment of aquacultures. Formation of drug resistance is a matter of general concern when antibiotics such as flumquine occur in the environment. Thus, biodegradation of flumequine in solution was investigated using five different ligninolytic fungi. Irpex lacteus, Dichomitus squalens, and Trametes versicolor proved most efficient and transformed more than 90% of flumequine within 6 or even 3 days. Panus tigrinus and Pleurotus ostreatus required up to 14 days to remove >90% of flumequine. Analyses of the metabolites by liquid chromatography-mass spectrometry suggest different transformation pathways for the different fungal strains. Structure proposals were elaborated for 8 metabolites. 7-Hydroxy-flumequine and flumequine ethyl ester were identified as common metabolites produced by all ligninolytic fungi. The largest variety of metabolites was formed by D. squalens. Residual antibacterial activity of the metabolite mixtures was tested using gram-positive and gram-negative bacteria. While for the less efficient P. tigrinus and P. ostreatus cultures the antibacterial activities corresponded to the residual concentrations of flumequine, a remarkable antibacterial activity remained in the D. squalens cultures although flumequine was transformed to more than 90%. Obviously, antibacterially active transformation products were formed by this fungal strain.

Microbial transformations of antimicrobial quinolones and related drugs

The quinolones are an important group of synthetic antimicrobial drugs used for treating bacterial diseases of humans and animals. Microorganisms transform antimicrobial quinolones (including fluoroquinolones) and the pharmacologically related naphthyridones, pyranoacridones, and cinnolones to a variety of metabolites. The biotransformation processes involve hydroxylation of methyl groups; hydroxylation of aliphatic and aromatic rings; oxidation of alcohols and amines; reduction of carboxyl groups; removal of methyl, carboxyl, fluoro, and cyano groups; addition of formyl, acetyl, nitrosyl, and cyclopentenone groups; and cleavage of aliphatic and aromatic rings. Most of these reactions greatly reduce or eliminate the antimicrobial activity of the quinolones.

Biodegradation of oxytetracycline by Pleurotus ostreatus mycelium: a mycoremediation technique

Oxytetracycline (OTC) is administered in high doses to livestocks and enters the environmental compartments as a consequence of animal waste disposal. As a first step in setting up a useful mycoremediation technique, an OTC lab degradation test was performed in liquid medium using the ligninolytic fungus Pleurotus ostreatus. OTC disappearance in culture medium was clearly evident as early as the third day of exposure onwards, with an almost complete removal after 14d. The drug removal was mediated by fungal absorption in the mycelia, where the OTC molecule underwent a degradation step, as demonstrated by mass spectrometry analyses. A putative degradation product, ADOTC (2-acetyl-2-decarboxamido-oxytetracycline) is proposed. Experimental conditions excluded OTC abiotic degradation; the degradation by extracellular laccase was also experimentally discarded.

Metabolism of a fungicide mepanipyrim by soil fungus Cunninghamella elegans ATCC36112

Mepanipyrim is a fungicide against several plant pathogens. However, no metabolic details have been established in fungi, which is the most important biomass in the natural environment. Cunninghamella elegans is a well-known fungal species with its strong resemblance to the mammalian xenobiotic metabolism. In this study, the detailed metabolic pathways of mepanipyrim were investigated with C. elegans. Approximately 87% of mepanipyrim was removed within 12 h with concomitant accumulation of nine metabolites. Structures of the metabolites were fully or tentatively identified with GC-MS and (1)H NMR. To determine the possible role of representative oxidative enzymes, piperonyl butoxide and methimazole were treated, and the kinetic responses of mepanipyrim and its metabolites were measured. Dose-dependent inhibition of metabolism was observed with piperonyl butoxide, while methimazole also inhibited the metabolism less effectively. The results indicate the possible involvement of cytochrome P450 and flavin-dependent monooxygenase in mepanipyrim metabolism. Comprehensive metabolic pathways can be deduced from the detailed analysis of metabolite profiles in control and inhibitor assays.

Biotransformation of flurbiprofen by Cunninghamella species

The biotransformation of the fluorinated anti-inflammatory drug flurbiprofen was investigated in Cunninghamella spp. Mono- and dihydroxylated metabolites were detected using gas chromatography-mass spectrometry and fluorine-19 nuclear magnetic resonance spectroscopy, and the major metabolite 4'-hydroxyflurbiprofen was isolated by preparative high-pressure liquid chromatography (HPLC). Cunninghamella elegans DSM 1908 and C. blakesleeana DSM 1906 also produced a phase II (conjugated) metabolite, which was identified as the sulfated drug via deconjugation experiments.

Degradation of oxolinic acid and flumequine in aquaculture pond waters and sediments

Oxolinic acid (OA) and flumequine (FLU) are two of the quinolone antibiotics (QAs) that are widely used in aquaculture. The purpose of this study was to understand the fates of OA and FLU in waters and sediment slurries from aquaculture ponds in a laboratory experiment. Waters and sediments were sampled from an eel (Anguilla japonica) pond and a shrimp (Penaeus vannamei) pond. The effects of light, microbial activities, and temperature on the degradation of these two QAs were elucidated. Results indicated that light plays a major role in the degradation of OA and FLU in waters and sediment slurries. Under illuminated and non-sterile conditions, the half-lives (t(1/2)) of OA were 2.3-4.8 and 9.5-15.0 days in the waters and sediment slurries, respectively. For FLU, under the same conditions, t(1/2) values were 1.9-2.3 and 3.6-6.4 days, respectively. Photodegradation of OA and FLU was much faster in water than in sediment slurry. In both environments, degradation became very slow or would plateau after only minimal change in the dark. Besides the effect of light, biodegradation had very minor effects on the degradation of the two QAs in the sediment slurries. The only independent biodegradation was found when OA was placed in shrimp pond sediment slurry, but at a much lower rate (t(1/2) of 98.7 days) than in light. Biodegradation of FLU was also found in the eel pond sediment slurry but only through an additional connection with light. Also, re-addition enhanced the degradation of OA in shrimp pond sediment slurry, but slowed the degradation of FLU in the eel pond sediment slurry in the dark. The temperature experiment in this study showed no significant effects on degradation of the two QAs in either pond waters or sediment slurries.