Removal of pharmaceuticals in pre-denitrifying MBBR – Influence of organic substrate availability in single- and three-stage configurations

Due to the limited efficiency of conventional biological treatment, innovative solutions are being explored to improve the removal of trace organic chemicals in wastewater. Controlling biomass exposure to growth substrate represents an appealing option for process optimization, as substrate availability likely impacts microbial activity, hence organic trace chemical removal. This study investigated the elimination of pharmaceuticals in pre-denitrifying moving bed biofilm reactors (MBBRs), where biofilm exposure to different organic substrate loading and composition was controlled by reactor staging. A three-stage MBBR and a single-stage reference MBBR (with the same operating volume and filling ratio) were operated under continuous-flow conditions (18 months). Two sets of batch experiments (day 100 and 471) were performed to quantify and compare pharmaceutical removal and denitrification kinetics in the different MBBRs. Experimental results revealed the possible influence of retransformation (e.g., from conjugated metabolites) and enantioselectivity on the removal of selected pharmaceuticals. In the second set of experiments, specific trends in denitrification and biotransformation kinetics were observed, with highest and lowest rates/rate constants in the first (S1) and the last (S3) staged sub reactors, respectively. These observations were confirmed by removal efficiency data obtained during continuous-flow operation, with limited removal (<10%) of recalcitrant pharmaceuticals and highest removal in S1 within the three-stage MBBR. Notably, biotransformation rate constants obtained for non recalcitrant pharmaceuticals correlated with mean specific denitrification rates, maximum specific growth rates and observed growth yield values. Overall, these findings suggest that: (i) the long-term exposure to tiered substrate accessibility in the three-stage configuration shaped the denitrification and biotransformation capacity of biofilms, with significant reduction under substrate limitation; (ii) biotransformation of pharmaceuticals may have occurred as a result of cometabolism by heterotrophic denitrifying bacteria. (C) 2017 Elsevier Ltd. All rights reserved

Effects of tetracycline, sulfonamide, fluoroquinolone, and lincosamide load in pig slurry on lettuce: Agricultural and human health implications

The application of pig slurry as fertilizer in agriculture provides nutrients, but it can also contain veterinary medicines, including antibiotic residues (ABs), which can have an ecotoxicological impact on agroecosystems. Furthermore, uptake, translocation, and accumulation of ABs in crops can mobilize them throughout the food chain. This greenhouse study aims to assess AB uptake from soil fertilized with pig slurry and its phenotypical effects on Lactuca sativa LThe authors gratefully acknowledge the financial support of the Spanish Ministry of Science and Innovation through project AGL 2017- 89518-R. IDAEA-CSIC is a Severo Ochoa Centre of Excellence (Spanish Ministry of Science and Innovation, Project CEX 2018-000794-S). Monica Escola Casas wishes to thank the Beatriu de Pinos 2018 grant program (MSCA grant agreement number 801370) for the funding. The authors likewise thank Miquel Massip, Daniel Fenero, and Nerea Gran- ados for their technical assistance in the greenhouse facilityPostprint (published version

Glyphosate has limited short-term effects on commensal bacterial community composition in the gut environment due to sufficient aromatic amino acid levels

Recently, concerns have been raised that residues of glyphosate-based herbicides may interfere with the homeostasis of the intestinal bacterial community and thereby affect the health of humans or animals. The biochemical pathway for aromatic amino acid synthesis (Shikimate pathway), which is specifically inhibited by glyphosate, is shared by plants and numerous bacterial species. Several in vitro studies have shown that various groups of intestinal bacteria may be differently affected by glyphosate. Here, we present results from an animal exposure trial combining deep 16S rRNA gene sequencing of the bacterial community with liquid chromatography mass spectrometry (LC-MS) based metabolic profiling of aromatic amino acids and their downstream metabolites. We found that glyphosate as well as the commercial formulation Glyfonova®450 PLUS administered at up to fifty times the established European Acceptable Daily Intake (ADI = 0.5 mg/kg body weight) had very limited effects on bacterial community composition in Sprague Dawley rats during a two-week exposure trial. The effect of glyphosate on prototrophic bacterial growth was highly dependent on the availability of aromatic amino acids, suggesting that the observed limited effect on bacterial composition was due to the presence of sufficient amounts of aromatic amino acids in the intestinal environment. A strong correlation was observed between intestinal concentrations of glyphosate and intestinal pH, which may partly be explained by an observed reduction in acetic acid produced by the gut bacteria. We conclude that sufficient intestinal levels of aromatic amino acids provided by the diet alleviates the need for bacterial synthesis of aromatic amino acids and thus prevents an antimicrobial effect of glyphosate in vivo. It is however possible that the situation is different in cases of human malnutrition or in production animals

Occurrence of antibiotics in Lettuce (Lactuca sativa L.) and Radish (Raphanus sativus L.) following organic soil fertilisation under plot-scale conditions: Crop and human health implications

Recent studies have demonstrated the crop uptake of antibiotics (ABs) from soils treated with AB-carrying fertilisers. However, there is a lack of plot-scale studies linking their effects at the agronomic and metabolomic/transcriptomic level to their impact on human health. This paper assesses the plant uptake of 23 ABs following two productive cycles of lettuce and radish cropped with sewage sludge, pig slurry, the organic fraction of municipal solid waste, or chemical fertilisation under plot-scale conditions (32 plots spanning 3-10 m2 each). AB uptake by plants depended on both the vegetable and the AB class and was higher in radish than in lettuce edible parts. Levels ranged from undetectable to up to 76 ng/g (fresh weight). Repetitive organic fertilisation resulted in an increase in the concentration of ABs in lettuce leaves, but not in radish roots. Significant metabolomic and transcriptomic changes were observed following soil fertilisation. Nevertheless, a human health risk assessment indicates that the occurrence of ABs in lettuce or radish edible parts does not pose any risk. To our knowledge, this is the first holistic plot-scale study demonstrating that the use of organic fertilisers containing ABs is safe for crop security and human health.The authors gratefully acknowledge the financial support of the Spanish Ministry of Science and Innovation through projects AGL2017- 89518-R and RTI2018-096175-B-I00. IDAEA-CSIC is a Severo Ochoa Centre of Excellence (Spanish Ministry of Science and Innovation, Project CEX2018-000794-S). Mònica Escolà Casas wishes to thank the Beatriu de Pinós 2018 grant programme (MSCA grant agreement number 801370) for the funding.Peer ReviewedPostprint (published version

Assessment of a novel microalgae-cork based technology for removing antibiotics, pesticides and nitrates from groundwater

Groundwater pollution has increased in recent years due to the intensification of agricultural and livestock activities. This results in a significant reduction in available freshwater resources. Here, we have studied the long term assessment of a green technology (1-4 L/day) based on a photobioreactor (PBR) containing immobilised microalgae-bacteria in polyurethane foam (PF) followed by a cork filter (CF) for removing nitrates, pesticides (atrazine and bromacil), and antibiotics (sulfamethoxazole and sulfacetamide) from groundwater. The prototype was moderately effective for removing nitrates (58%) at an HRT of 8 days, while its efficiency decreased at a HRT of 4 and 2 days (<20% removal). The combined use of PBR-CF enabled antibiotics and pesticides to be attenuated by up to 95% at an HRT of 8 days, but their attenuation decreased with shorter HRT, with pesticides being the compounds most affected (reducing from 97 to 98% at an HRT of 8 days to 23-45% at an HRT of 2 days). Pesticide transformation products were identified after the CF, supporting biodegradation as the main attenuation process. A gene-based metataxonomic assessment linked the attenuation of micropollutants to the presence of specific pesticide biodegradation species (e.g. genus Phenylobacterium, Sphingomonadaceae, and Caulobacteraceae). Therefore, the results highlighted the potential use of microalgae and cork to treat polluted groundwater.The authors wish to thank the financial support of the European Union through the project LIFE18 ENV/ES/000199 and the Spanish Ministry of Science, Innovation and Universities through Project CTM2017-91355-EXP. Finally, European Commission (Erasmus program) and Government of Chile for supporting Lorenzo Rambaldo and Héctor Avila Cortés's visit at IDAEA-CSIC in Barcelona, Spain.Peer reviewe

Linking plant-root exudate changes to micropollutant exposure in aquatic plants (Lemna minor and Salvinia natans). A prospective metabolomic study

Recent findings indicate that plant-root exudates can stimulate plant-associated microorganisms to enhance the biodegradation of contaminants in constructed wetlands. To understand this process, we studied the root-exudation changes of two aquatic plants (Lemna minor and Salvinia natans) upon micropollutants exposure (10, 100 and 1000 μg/L mixes containing naproxen, diclofenac, carbamazepine, and benzotriazole). After a 2-day exposure, plant exudates were collected, extracted and non-target analysis was performed with a gas chromatography–high resolution Orbitrap mass-spectrometer. Plants didn't show morphological or growth differences between the control and spiked reactors, but exudation changes were observed in both plants at all concentration levels. Partial least squares discriminant analysis showed that, for Lemna minor, the increase of micropollutants exposure was linked to the reduction of sugar and fatty acid exudation. This may trigger changes in the microbial community living on complex carbon forms. Instead, in Salvinia natans, micropollutants exposure was linked to the release of long-chain compounds such as cuticular waxes and sesquiterpenoids, which might be related to stress signaling. These results demonstrate that plant micropollutant-exposure at environmentally relevant concentration levels triggers changes in root exudates. This may help to design new strategies to enhance micropollutants degradation in nature based solutions such as in constructed wetlands.The authors acknowledge the financial support of the Spanish Ministry of Science, Innovation and Universities under Project CTM2017-91355-EXP. Mònica Escolà Casas thanks the Beatriu de Pinós 2018 grant-programme (MSCA grant agreement number 801370) for the funding. IDAEA-CSIC is a Centre of Excellence Severo Ochoa (Spanish Ministry of Science and Innovation, Project CEX2018-000794-S). The authors also want to thank the technicians Sandra Pulgar García and Yolanda Rodríguez Espelta for taking care of the plants and for the help provided in the laboratory tasks.Peer reviewe

Analytical challenges and solutions for performing metabolomic analysis of root exudates

Plant stress responses are mediated by the release of chemical compounds called exudates into the rhizosphere. These chemical substances include primary and secondary plant metabolites and play an important role in the plant defense mechanism. The identification, characterization and study of these compounds can open the door to numerous applications, from greener agriculture to enhanced phytoremediation. This paper critically reviews the most relevant sampling strategies, analytical methodologies, and data-mining approaches to study root exudates.Common analytical techniques are grounded in mass spectrometry or nuclear mass spectrometry, but less common biospectroscopy techniques could offer a new perspective in plant metabolomics due to the minimal sample processing they require. Finally, after analysis, the collected raw data must then be analyzed by means of different multivariate and univariate statistical approaches to test biological-response hypotheses. All in all, the assessment of root exudates calls for the development of hyphenated analytical methodologies, as well as efforts to consolidate data-preprocessing workflows.The authors gratefully acknowledge the financial support of the Spanish Ministry of Science, Innovation, and Universities under Project CTM2017-91355-EXP. Mònica Escolà Casas wants to thank the Beatriu de Pinós 2018 grant-programme (MSCA grant agreement number 801370) for the funding. IDAEA-CSIC is a Centre of Excellence Severo Ochoa (Spanish Ministry of Science and Innovation, Project CEX2018-000794-S).Peer reviewe