Carlos E. Rodríguez-Rodríguez

Removal of pharmaceuticals, polybrominated flame retardants and UV-filters from sludge by the fungus Trametes versicolor in bioslurry reactor

Conventional wastewater treatments are inefficient in the removal of many organic pollutants. The presence of these contaminants in the final sludge represents a source of environmental pollution due to the increasing use of biosolids in land application. A biotechnological approach which employed the fungus Trametes versicolor in a sludge-bioslurry reactor was assessed in order to remove several groups of emerging pollutants. Biological fungal activity was monitored by means of ergosterol and laccase determinations. Fifteen out of 24 detected pharmaceuticals were removed at efficiencies over 50% after the treatment, including eight completely degraded. Removal ranged between 16-53% and 22-100% for the brominated flame retardants and the UV-filters, respectively. Only two of all the detected compounds remained unchanged after the treatment. Although elimination results are promising, the toxicity of the final sludge increased after the treatment. This finding is contrary to the toxicity results obtained in similar treatments of sludge with T. versicolor in solid-phase.

Bioaugmentation of sewage sludge with Trametes versicolor in solid-phase biopiles produces degradation of pharmaceuticals and affects microbial communities

The use of sludge (biosolids) in land application may contribute to the spread of organic micropollutants as wastewater treatments do not completely remove these compounds. Therefore, the development of alternative strategies for sludge treatment is a matter of recent concern. The elimination of pharmaceuticals at pre-existent concentrations from sewage sludge was assessed, for the first time, in nonsterile biopiles by means of fungal bioaugmentation with Trametes versicolor (BTV-systems) and compared with the effect of autochthonous microbiota (NB-systems). The competition between the autochthonous fungal/bacterial communities and T. versicolor was studied using denaturing gradient gel electrophoresis (DGGE) and the cloning/sequencing approach. An inhibitory effect exerted by T. versicolor over bacterial populations was suggested. However, after 21 days, T. versicolor was no longer the main taxon in the fungal communities. The elimination profiles revealed an enhanced removal of atorvastatin-diclofenac-hydrochlorothiazide (during the whole treatment) and ranitidine-fenofibrate (at short periods) in the BTV biopiles in respect to NB biopiles, coincident with the presence of the fungus. For ibuprofen-clarithromycin-furosemide, the elimination profiles were similar irrespective of the system, and with carbamazepine no significant degradation was obtained. The results suggest that a fungal treatment with T. versicolor could be a promising process for the remediation of some pharmaceuticals in complex matrices such as biosolids.

On-farm biopurification systems: role of white rot fungi in depuration of pesticide-containing wastewaters.

Environmental contamination with pesticides is an undesired consequence of agricultural activities. Biopurification systems (BPS) comprise a novel strategy to degrade pesticides from contaminated wastewaters, consisting of a highly active biological mixture confined in a container or excavation. The design of BPS promotes microbial activity, in particular by white rot fungi (WRF). Due to their physiological features, specifically the production of highly unspecific ligninolytic enzymes and some intracellular enzymatic complexes, WRF show the ability to transform a wide range of organic pollutants. This minireview summarizes the potential participation of WRF in BPS. The first part presents the potential use of WRF in biodegradation of pollutants, particularly pesticides, and includes a brief description of the enzymatic systems involved in their oxidation. The second part presents an outline of BPS, focusing on the elements that influence the participation of WRF in their operation, and includes a summary of the studies regarding the fungal-mediated degradation of pesticides in BPS biomixtures and other solid-phase systems that mimic BPS.

Biodegradation of Pharmaceuticals by Fungi and Metabolites Identification

Pharmaceutical compounds comprise a widely employed group of therapeutic agents now considered as emerging micropollutants. This chapter summarizes the state of the art in the degradation of pharmaceuticals by fungi in liquid matrices (with emphasis on white-rot fungi), including the use of both whole cells and fungal enzymes. The identification of the metabolites produced as well as the proposed degradation pathways available for some drugs are discussed. The information is organized according to the activity of the pharmaceutical compounds, grouped in: anti-inflammatory/analgesic drugs, psychiatric drugs, lipid regulators, antibiotics and other antimicrobial agents, b-blockers, estrogens, and iodinated contrast media. Considering the interest in potential application of fungal treatments in future real scale bioremediation of effluents, the ecotoxicology of the process is included when available.

Naproxen degradation test to monitor Trametes versicolor activity in solid-state bioremediation processes

The white-rot fungus Trametes versicolor has been studied as a potential agent for the removal of environmental pollutants. For long-time solid-phase bioremediation systems a test is required to monitor the metabolic status of T. versicolor and its degradation capability at different stages. A biodegradation test based on the percentage of degradation of a spiked model pharmaceutical (anti-inflammatory naproxen) in 24 h (ND24) is proposed to monitor the removal of pharmaceuticals and personal care products in sewage sludge. ND24 is intended to act as a test complementary to ergosterol quantification as specific fungal biomarker, and laccase activity as extracellular oxidative capacity of T. versicolor. For samples collected over 45 d, ND24 values did not necessarily correlate with ergosterol or laccase amounts but in most cases, they were over 30% degradation, indicating that T. versicolor may be suitable for bioremediation of sewage sludge in the studied period.

Effects of oxytetracycline on the performance and activity of biomixtures: Removal of herbicides and mineralization of chlorpyrifos

Biopurification systems (BPS) are design to remove pesticides from agricultural wastewater. This work assays for the first time the potential effect of an antibiotic of agricultural use (oxytetracycline, OTC) on the performance of a biomixture (biologically active core of BPS), considering that antibiotic-containing wastewaters are also produced in agricultural labors. The respiration of the biomixture was stimulated in the presence of increasing doses of OTC (≥100mgkg-1), and only slightly increased with lower doses (≤10mgkg-1). When co-applied during the removal of chlorpyrifos, OTC increased chlorpyrifos mineralization rates at low doses, resembling a hormetic effect. The biomixture was also able to remove three herbicides (atrazine, ametryn and linuron) with half-lives of 24.3 d, 43.9 d and 30.7 d; during co-application of OTC at a biomixture-relevant concentration, only the removal of ametryn was significantly inhibited, increasing its half-life to 92.4 d. Ecotoxicological assays revealed that detoxification takes place in the biomixture during the removal of herbicides in the presence of OTC. Overall results suggest that co-application of OTC in a biomixture does not negatively affect the performance of the matrix in every case; moreover, the co-application of this antibiotic could improve the mineralization of some pesticides.

Fungal contamination of stored automobile-fuels in a tropical environment.

Because of the lack of reports, the base levels of microbial contamination on stored fuels are unknown in tropical regions and it is unclear whether these levels have some influence on fuel quality parameters. Therefore, fungal quality in automobile fuels stored across Costa Rican territory was evaluated during two years according to the standard ASTM D6974-04. For a total of 96 samples, counts and identification of molds and yeasts were performed on regular gas, premium gas and diesel taken from the bottom and superior part of the container tanks. The highest contamination was found on the bottom of the tanks, where an aqueous phase was usually identified, showing populations over the ones present in the hydrocarbon itself (up to 10(8) CFU/L). Diesel was the most contaminated fuel (up to 10(7) CFU/L); however, an alteration on the physicochemical parameters was not observed in any kind of fuel. Seventy-five mold strains were isolated, Penicillium sp. being the most common genus (45.8% of the samples), and ten yeast strains, from the genera Candida sp. and Rhodotorula sp. Four of the yeasts were able to grow on diesel as the sole carbon source, at concentrations ranging from 0.5% to 25%. Increasing the frequency of tank cleaning, adding antimicrobial agents and monitoring microbial populations are recommended strategies to improve microbial quality of stored fuels.

Optimization of a Fungally Bioaugmented Biomixture for Carbofuran Removal in On-Farm Biopurification Systems

Biomixtures comprise the active part of biopurification systems (BPS) for the removal of pesticide-containing wastewater from agricultural origin. Considering that biomixtures contain an important amount of lignocellulosic substrates, their bioaugmentation with degrading ligninolytic fungi represents a promising way to improve BPS. The fungus Trametes versicolor was employed for the bioaugmentation of rice husk-compost-soil (GCS) biomixtures in order to optimize the removal of the highly toxic insecticide/nematicide carbofuran (CFN). Composition of biomixtures has not been optimized before, and usually, a volumetric composition of 50:25:25 (lignocellulosic substrate:humic component:soil) is employed. Optimization of the biomixture composition was performed with a central composite design, using the volumetric content of rice husk (pre-colonized by the fungus) and the volumetric ratio compost/soil as design variables. Performance of biomixtures was comprehensively assayed considering CFN removal, the production of toxic transformation products (3-hydroxycarbofuran/3-ketocarbofuran), the ability to mineralize [14C]carbofuran, and the residual toxicity in the matrix. According to the models, the optimal volumetric composition of the GCS biomixture is 30:43:27, which maximizes removal and mineralization rate, and minimizes the accumulation of transformation products. Results support the value of assessing new biomixture formulations according to the target pesticide in order to obtain their optimal performance, before their use in BPS.

Ecotoxicological analysis during the removal of carbofuran in fungal bioaugmented matrices

Biomixtures are used for the removal of pesticides from agricultural wastewater. As biomixtures employ high content of lignocellulosic substrates, their bioaugmentation with ligninolytic fungi represents a novel approach for their enhancement. Nonetheless, the decrease in the concentration of the pesticide may result in sublethal concentrations that still affect ecosystems. Two matrices, a microcosm of rice husk (lignocellulosic substrate) bioaugmented with the fungus Trametes versicolor and a biomixture that contained fungally colonized rice husk were used in the degradation of the insecticide/nematicide carbofuran (CFN). Elutriates simulating lixiviates from these matrices were used to assay the ecotoxicological effects at sublethal level over Daphnia magna (Straus) and the fish Oreochromis aureus (Steindachner) and Oncorhynchus mykiss (Walbaum). Elutriates obtained after 30 d of treatment in the rice husk microcosms at dilutions over 2.5% increased the offspring of D. magna as a trade-off stress response, and produced mortality of neonates at dilutions over 5%. Elutriates (dilution 1:200) obtained during a 30 d period did not produce alterations on the oxygen consumption and ammonium excretion of O. mykiss, however these physiological parameters were affected in O. aureus at every time point of treatment, irrespective of the decrease in CFN concentration. When the fungally colonized rice husk was used to prepare a biomixture, where more accelerated degradation is expected, similar alterations on the responses by O. aureus were achieved. Results suggest that despite the good removal of the pesticide, it is necessary to optimize biomixtures to minimize their residual toxicity and potential chronic effects on aquatic life.

Accelerated biodegradation of selected nematicides in tropical crop soils from Costa Rica

Degradation and mineralization behavior of selected nematicides was studied in soil samples from fields cultivated with banana, potato, and coffee. Degradation assays in most of the studied soils revealed shorter half-lives for carbofuran (CBF) and ethoprophos (ETP) in samples with a history of treatment with these compounds, which may have been caused by enhanced biodegradation. A short half-life value for CBF degradation was also observed in a banana field with no previous exposure to this pesticide, but with a recent application of the carbamate insecticide oxamyl, which supports the hypothesis that preexposure to oxamyl may cause microbial adaptation towards degradation of CBF, an observation of a phenomenon not yet tested according to the literature reviewed. Mineralization assays for CBF and terbufos (TBF) revealed that history of treatment with these nematicides did not cause higher mineralization rates in preexposed soils when compared to unexposed ones, except in the case of soils from coffee fields. Mineralization half-lives for soils unexposed to these pesticides were significantly shorter than most reports in the literature in the same conditions. Mineralization rates for soils with a previous exposure to these pesticides were also obtained, adding to the very few reports found. This paper contributes valuable data to the low number of reports dealing with pesticide fate in soils from tropical origin.