•Scenedesmus obliquus was tolerant to SMZ, SMX, and their mixture, and could withstand their high doses.•96 h EC50 of SMZ, SMX, and their mixture for S. obliquus was 1.23, 0.12, and 0.89 mg L-1.•The ...risk quotients of SMZ, SMX, and their mixture were >1.•The removal of SMZ and SMX was more in the mixture than their individual medium.•Metabolic pathways of SMZ and SMX by S. obliquus were proposed.
This study investigated the environmental effects of two common emerging contaminants, sulfamethazine (SMZ) and sulfamethoxazole (SMX), and their mixture using a green microalga, Scenedesmus obliquus. The calculated EC50 values of SMZ, SMX, and their mixture (11:1 wt/wt) after 96 h were 1.23, 0.12, and 0.89 mg L-1, respectively. The toxicity of the mixture could be better predicted using a concentration addition model than an independent action model. The risk quotients of SMZ, SMX, and their mixture were >1 during the experiment, indicating their high potential risks on aquatic microorganisms. Despite their toxicity, S. obliquus exhibited 17.3% and 29.3% removal of 0.1 mg L-1 and 0.2 mg L-1 after 11 days of cultivation. The changes of SMZ and SMX removal were observed when combined, which showed a significantly improved removal of SMZ (up to 3.4 folds) with addition of SMX (0.2 mg L-1). The metabolic pathways of SMZ and SMX were proposed according to mass spectroscopic analysis, which showed six metabolites of SMX and seven intermediates of SMZ, formed as a result of ring cleavage, hydroxylation, methylation, nitrosation, and deamination.
•Ecotoxicological effect of enrofloxacin on Lolium perenne L. was investigated.•Efficient removal (94.33%) of enrofloxacin was achieved by Lolium perenne L.•Biodegradation has been the main mechanism ...for enrofloxacin removal.•Multiple metabolic pathways of enrofloxacin was proposed.•Key metabolic genes were identified by transcriptomics and network analysis.
Contamination of fluoroquinolones (FQs) are of emerging concerns because of their adverse effects on environment and humans. This study investigated the ecotoxicological effects, biodegradation, and multiple metabolic pathways of a frequently found FQ, enrofloxacin (ENR) by ryegrass (Lolium perenne L.). Key metabolic genes for driving the metabolism of ENR have been identified using transcriptome profiling of L. perenne and gene network analysis. Toxicity of ENR on ryegrass has been evaluated according to the morphological changes, lipid peroxidation content, and antioxidant enzymatic activities. Moreover, there was 94.33%, 71.58%, 57.22%, and 55.23% removal of 1, 10, 50 and 100 mg L−1 ENR, respectively, which was mainly achieved by biodegradation according to the mass balance. A biodegradation pathway has been proposed by incorporating mass spectrums of extracted ENR intermediates with their formation dynamics. Analysis of differentially expressed genes (DEGs) and their network unraveled that the genes encoding monooxygenase, oxidative carboxylase, methyltransferase, lyase, hydroxylase, dehydrogenase, and peroxidase were the key functional genes. These enzymes can induce di/hydroxylation, decarboxylation, methylation, and bond and ring cleavage of ENR for its effective degradation. This study demonstrated that ryegrass can be used for efficient treatment of ENR polluted water and extended the understanding of the molecular mechanism of antibiotics’ biodegradation in plants.
•Toxicological effects of carbamazepine on C. mexicana and S. obliquus was studied.•C. mexicana was tolerant to carbamazepine, and could withstand at its high dose.•Carbamazepine influenced the ...biochemical characteristics of microalgal cells.•SOD and CAT activity was increased in algae under toxic stress of carbamazepine.•Microalgal strains showed simultaneous bioaccumulation and biodegradation of CBZ.
This study evaluated the toxicity and cellular stresses of carbamazepine (CBZ) on Chlamydomonas mexicana and Scenedesmus obliquus, and its biodegradation by both microalgal species. The growth of both microalgal species decreased with increase of CBZ concentration. The growth of S. obliquus was significantly inhibited (97%) at 200 mg CBZ L−1, as compared to the control after 10days; whereas, C. mexicana showed 30% inhibition at the same experimental conditions. Biochemical characteristics including total chlorophyll, carotenoid contents and enzyme activities (SOD and CAT) for both species were affected by CBZ at relatively high concentration. C. mexicana and S. obliquus could achieve a maximum of 35% and 28% biodegradation of CBZ, respectively. Two metabolites (10,11-dihydro-10,11-expoxycarbamazepine and n-hydroxy-CBZ) were identified by UPLC-MS, as a result of CBZ biodegradation by C. mexicana. This study demonstrated that C. mexicana was more tolerant to CBZ and could be used for treatment of CBZ contaminated wastewater.
Pharmaceutical contaminants (PCs) have been recognized as emerging contaminants causing unexpected consequences to environment and humans. There is an urgent need for development of efficient ...technologies to treat these PCs from water. The current study has investigated the removal capacity of a green microalgal species,
Scenedesmus obliquus
, for doxylamine, chemical oxygen demand (COD), and nutrients from real wastewater. Results have indicated that
S. obliquus
can grow well in the doxylamine-polluted wastewater with the achievement of 56, 78.5, 100, and 89% removal of doxylamine, COD, total nitrogen (TN), and total phosphorus (TP). Addition of 2 g L
−1
bicarbonate enhanced the removal of doxylamine up to 63% and slightly inhibited the removal of COD. Decreased carbohydrate (28–26%) and increased protein content (30–33%) of the harvested biomass have been observed after cultivation in the wastewater. The current study has shown the feasibility of using microalgae-based biotechnologies for PC-contaminated wastewater.
Whether bisphenols, as plasticizers, can influence bacterial uptake of antibiotic resistance genes (ARGs) in natural environment, as well as the underlying mechanism remains largely unknown. Our ...results showed that four commonly used bisphenols (bisphenol A, S, F, and AF) at their environmental relative concentrations can significantly promote transmission of ARGs by 2.97–3.56 times in Acinetobacter baylyi ADP1. Intriguingly, we observed ADP1 acquired resistance by integrating plasmids uptake and cellular metabolic adaptations other than through reactive oxygen species mediated pathway. Metabolic adaptations including upregulation of capsules polysaccharide biosynthesis and intracellularly metabolic enzymes, which enabled formation of thicker capsules for capturing free plasmids, and degradation of accumulated compounds. Simultaneously, genes encoding DNA uptake and translocation machinery were incorporated to enhance natural transformation of antibiotic resistance carrying plasmids. We further exposed aquatic fish to bisphenols for 120 days to monitor their long-term effects in aquatic environment, which showed that intestinal bacteria communities were dominated by a drug resistant microbiome. Our study provides new insight into the mechanism of enhanced natural transformation of ARGs by bisphenols, and highlights the investigations for unexpectedly-elevated antibiotic-resistant risks by structurally related environmental chemicals.
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•Bisphenols significantly promote ARGs transformation in Acinetobacter baylyi ADP1.•Bisphenols elevated ARGs not via ROS-mediated pathway.•Bisphenols increased cellular adaptative changes and plasmids uptake for resistance.•Long-term bisphenols exposure in aquatic environment induced ARGs carrying microbiome.
Sulfonamides (SAs) has been frequently found in environment with numerous adverse effects on ecological system and human. In this study, we investigated the toxicity of sulfacetamide (SFM) on a ...benthic microalgal species, as well as its metabolic mechanisms. Results of flow cytometry demonstrated significant inhibition on growth and cell viability of Desmodesmus quadricauda under 0.1–3 mg L−1 SFM. Half-maximum effective concentrations (EC50) of SFM were calculated to be 1.224, 1.324, 0.845, 1.178 and 1.754 mg L−1 at day 2, 4, 6, 8 and 10. Biochemical characteristics including total chlorophyll, carotenoid, malonaldehyde, and activities of antioxidant enzymes (superoxide dismutase and peroxidase) were significantly influenced by SFM. Principal component analysis showed a close correlation among the cellular contents. Moreover, identified intermediates showed that D. quadricauda can biodegrade SFM through hydroxylation, decarboxylation, bond cleavage and deamination. Acute and chronic toxicity test of the metabolic byproducts indicated the formed intermediates were with less toxicity than their parent compound. This study has extended the understanding of the microalgal tolerance and metabolic mechanisms toward SA antibiotic.
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•Ecotoxicity of sulfacetamide was evaluated using a standard microalga species.•96 h EC50 of sulfacetamide was 1.324 mg L-1.•Microalgal metabolic pathway of sulfacetamide was proposed for a first time.•Acute and chronic toxicity of identified intermediates were evaluated.
Textile dyes are xenobiotic contaminants which pose a potential risk on the ecosystem upon their disposal to the water bodies. This study evaluated the efficiencies of different immobilization ...matrices for its utilization in a reactor with continuous mode operation for decolorization of textile effluent. An effective consortium of bacteria (Brevibacillus laterosporus) and yeast (Galactomyces geotrichum) were immobilized in different support matrices including calcium alginate, polyvinyl alcohol, stainless steel sponge and polyurethane foam to investigate the decolorization of a model azo dye, Remazol red and textile industry effluent. The microbial consortia immobilized in stainless steel sponge and polyurethane foam exhibited 100% decolorization of 50 mg L−1 Remazol red in 11 and 15 h, respectively; however, calcium alginate and polyvinyl alcohol required considerably more time (20 and 24 h, respectively) for complete decolorization. Among all the matrices, The calcium alginate, stainless steel sponge and polyurethane foam showed >95% decolorization of textile industry effluent within 48 h. The calcium alginate and polyvinyl alcohol exhibited stable performance of decolorization with its repeated use for 5 cycles with >76% decolorization. An upflow fixed bed reactor (total volume- 215 mL) packed with the immobilized cells of consortium onto stainless steel sponge attained ∼90% decolorization of textile industry effluent in continuous operation at 10 mL h−1. The decolorization efficiency of the reactor was well maintained (>90%) when the reactor was used repeatedly for three cycles. The overall results indicated that immobilized mixed consortium cells can be considered as an effective tool for its potential application in removal of xenobiotic textile dyes from the textile industry wastewater with >90% of decolorization efficiency.
•Effective microbial consortium was immobilized in different support matrices.•SS-sponge immobilized cells showed 100% decolorization of Remazol red in 11 h.•Calcium alginate, polyvinyl alcohol showed stable decolorization of textile effluent.•The upflow fixed bed reactor can be used for continuous decolorization of effluent.
Plants are readily exposed to the antibiotics residues in reclaimed water indicating an urgent need to comprehensively analyze their ecotoxicological effects and fate of these emerging contaminants. ...Here, we unraveled the dissemination of enrofloxacin (ENR) in a pasture grass, Lolium perenne L., and identified multistage defense systems as its adaptation mechanism. Uptaken concentrations of ENR ranged from 1.28 to 246.60 µg g−1 with bioconcentration factors (BCF) upto 15.13, and translocation factors (TF) upto 0.332. The antioxidant enzymatic activities such as superoxide dismutase, peroxidase, and catalase were increased by upto 115%. Further transcriptomics demonstrated that differentially expressed genes (DEGs) involved in glycolysis, tricarboxylic acid (TCA) cycle, oxidative phosphorylation, and glutathione metabolism were significantly up-regulated by 1.56–5.93, 3–7 and 1.04–6.42 times, respectively; whilst, the DEGs in nitrogen and sulfur metabolism pathways were significantly up-regulated by 1.06–5.64 and 2.64–3.54 folds. These processes can supply energy, signaling molecules, and antioxidants for detoxification of ENR in ryegrass. Such results provide understanding into fasting grass adaptability to antibiotics by enhancing the key protective pathways under organic pollutant stresses in environments.
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•Accumulated enrofloxacin in ryegrass leaves ranged from 1.28 to 246.60 µg g−1.•Significantly suppressed photosynthesis has been observed.•Network analysis showed key genes in energy metabolism, nitrogen metabolism, and sulfur metabolism.•A multistage defense mechanism in ryegrass plays essential role for detoxification of enrofloxacin.
Levofloxacin (LEV), a fluoroquinolone antibiotic has been frequently observed in water resources imposing ecotoxicological effects on aquatic microbiota. The biodegradation and metabolic fate of LEV ...via a microalga, Scenedesmus obliquus in synthetic saline wastewater were investigated in this study. LEV removal (1mgL−1) by S. obliquus was relatively low in the synthetic wastewater without the addition of sodium chloride (NaCl); however, its removal increased significantly from 4.5 to 93.4% with increasing of its salinity from 0 to 171mM NaCl. Kinetic studies showed that the removal rate constant (k) increased from 0.005 to 0.289d−1 and degradation half-life decreased from 272 to 5d in the presence of NaCl (0–856mM). The removal mechanism analysis showed that the major mechanism of NaCl mediated enhancement of LEV removal was the bioaccumulation and subsequent intracellular biodegradation of LEV in microalgal cells. Six metabolites were identified via gas chromatography–mass spectrometry analysis after biodegradation of LEV. A metabolic pathway was postulated with regard to various cellular biocatalytic reactions in S. obliquus, including decarboxylation, demethylation, dehydroxylation, side chain breakdown, and ring cleavage.
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•Scenedesmus obliquus was tolerant to levofloxacin, and could withstand its high doses.•96h EC50 of levofloxacin for C. vulgaris was 65mgL−1.•Addition of NaCl stimulated the biodegradation of levofloxacin up to 93.4%.•Scenedesmus obliquus can biotransform levofloxacin in simple metabolic byproducts.
2,2-Bis (4-hydroxyphenyl) propane (bisphenol A) is a precursor in many industrial and manufactural resins, plastics, and polycarbonate, as well as an endocrine disruptor in humans and animals. ...Therefore, the real-time sensing and in-situ removal of BPA are in strong demand. This study evaluated a method for the electrochemical detection of BPA using a carbon felt electrode. BPA was detected by cyclic voltammetry. During detection, the BPA was electropolymerized to a non-conductive lump and layer on the electrode surface. Simultaneously, the capacitance and electrochemical properties of the carbon felt decreased. The peak current and BPA concentration showed a linear correlation; the estimated detection limit was 4.78 × 10−7 M. The BPA-electropolymerized carbon felt could be regenerated successfully by ultrasonication. The detection and quantification of BPA in real water samples showed satisfactory recoveries of 98.4–101.0%. The carbon felt-based electrochemical analysis exhibited high sensitivity and reusability, making it applicable to the in-situ and on-site detection and removal of endocrine disruptors, such as BPA.
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•BPA was detected electrochemically without a complicated synthesis process.•Carbon felt could remove BPA from suspension by electropolymerization.•BPA was electropolymerized to a non-conductive lump on the carbon surface.•Sonication could regenerate the carbon felt by removing the polymeric BPA film.•The electrochemical detection limit of BPA was 4.78 × 10−7 M.
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