The increase in worldwide water contamination with numerous pharmaceutical contaminants (PCs) has become an emerging environmental concern due to their considerable ecotoxicities and associated ...health issues. Microalgae-mediated bioremediation of PCs has recently gained scientific attention, as microalgal bioremediation is a solar-power driven, ecologically comprehensive, and sustainable reclamation strategy. In this review, we comprehensively describe the current research on the possible roles and applications of microalgae for removing PCs from aqueous media. We summarize several novel approaches including constructing microbial consortia, acclimation, and cometabolism for enhanced removal of PCs by microalgae, which would improve practical feasibility of these technologies. Some novel concepts for degrading PCs using integrated processes and genetic modifications to realize algal-based bioremediation technologies are also recommended.
Water contamination with numerous pharmaceutical contaminants (PCs) has been one of the most important emerging environmental problems facing humanity due to their ecotoxicities and health issues.
Culturing microalgae in wastewater can create a ‘zero-waste concept’ and stimulate an effective and sustainable practice for the microalgae biofuel industry.
Constructing microbial consortia, acclimating microorganisms, and cometabolic approaches can improve the engineering feasibility of microalgae-based biotechnologies.
Some innovative concepts, such as integrated processes (algae-based technologies with advanced oxidation processes, constructed wetlands, and microbial fuel cells) and genetic modifications, can help to realize algae-based bioremediation technologies.
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•Chlorella vulgaris was tolerant to levofloxacin, and could withstand its high doses.•96h EC50 of levofloxacin for C. vulgaris was 58.6mgL−1.•The acclimation of C. vulgaris enhanced ...the removal of levofloxacin.•Sodium chloride stimulated the biodegradation of levofloxacin up to 91%.•NaCl (1%w/v) increased the degradation rate constant (k) of LEV from 0.011 to 0.257d−1.
The extensive contamination of levofloxacin (LEV) in aquatic ecosystems has attracted increasing attention because of the potential for development of bacterial resistance and its eco-toxicity to non-target organisms. Biodegradation of LEV was significantly improved upon the acclimation of a freshwater microalga, Chlorella vulgaris and in the presence of elevated salinity. Among the six wild species (Chlamydomonas mexicana, Chlamydomonas pitschmannii, Chlorella vulgaris, Ourococcus multisporus, Micractinium resseri, Tribonema aequale), C. vulgaris showed the highest removal capacity (12%) of LEV at 1mgL−1. The acclimated C. vulgaris, which was pre-exposed to 200mgL−1 of LEV for 11days, exhibited enhanced removal of 1mgLEVL−1 by 16% after 11days of cultivation. The addition of 1% (w/v) sodium chloride into the microalgal media significantly improved LEV removal by >80% in the C. vulgaris culture. The bioaccumulation of LEV at day 11 in C. vulgaris cells without NaCl was 34μgg−1, which was elevated to 101μgg−1LEV at 1% NaCl. The bioconcentration factor for LEV was 34 and 1004 in 0 and 1% NaCl, respectively. The mass balance analysis of LEV showed that more than 90% of LEV was biodegraded by C. vulgaris at day 11 with the addition of 1% NaCl. These results demonstrated that the enhanced removal of LEV by salinity was mainly through bioaccumulation and subsequent intracellular biodegradation by C. vulgaris cells.
A schematic summary of the mechanism employed by the plants for the uptake and, degradation/detoxification of emerging PPCP contaminants, and the potential applications and advances in ...phytoremediation for the sustainable treatment of contaminated environments.
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•Man-made activities are responsible for extensive pollution of water reservoirs.•Enzymatic catalysis is the major key mechanism of contaminant removal.•Novel engineered wetlands can act as complementary wastewater treatment strategy.•Advanced genetic methodologies should be employed to improve phytoremediation.
The industrial revolution in the production of pharmaceuticals and personal care products (PPCPs) has significantly improved public health in recent years. However, this development has also led to water pollution because of the unintentional disposal of these synthetic chemicals, creating unacceptable sanitary conditions. Conventional wastewater treatment systems can eliminate most of the contaminants, however these are not efficient in removing PPCPs. Plant-based remediation is a simple, yet very effective and eco-friendly approach that can complement existing wastewater treatment. Phytoremediation of emerging contaminants is relatively new, and various key concepts including the uptake and detoxification mechanisms remain relatively unexplored compared with microbial processes. This review comprehensively discusses the latest studies on the biochemistry and application of phytoremediation for the removal of PPCPs from wastewater, focusing on the mechanisms of uptake and detoxification through the enzymatic biotransformation of PPCPs and the latest field applications using innovative engineered systems. Future research recommendations are addressed, including the need of topics warranting investigation in PPCPs interactions with plant tissues, their metabolic transformation in plants, development of new predictive uptake models and futuristic advancements involving the cutting-edge methodologies in genetic engineering for the realization of advanced phytoremediation technologies. This review is an effort to gather the scattered information on research updates of phytoremediation in recent decade to present an outlook of the emerging, green biotechnology for the rehabilitation of the environment.
•Chlorella pyrenoidosa can withstand high concentrations of tetracycline.•Cometabolism constructed a metabolic enzymes-photosynthetic machinery.•Formation dynamics of degradation intermediates were ...monitored.•Key catabolic enzymes in degradation pathway of TC were identified.•Microalgae removed 53.2% to 91.7% of antibiotics from reclaimed water.
Cometabolism has shown great potential in increasing the engineering feasibility of microalgae-based biotechnologies for the aerobic treatment of antibiotics-polluted wastewaters. Yet, the underlying mechanisms involved in improved microalgal performance remain unknown. In this study, we incorporated transcriptomics, gene network analysis, and enzymatic activities with cometabolic pathways of tetracycline (TC) by Chlorella pyrenoidosa to identify the key driving factors. The results demonstrated that cometabolism constructed a metabolic enzymes-photosynthetic machinery to improve the electron transport chain and activities of catalytic enzymes, which resulted in subsequent 100% removal of TC. Coupling formation dynamics of the intermediates with roles of identified metabolic enzymes, degradation of TC can be induced by de/hydroxylation, de/hydrogenation, bond-cleavage, decarboxylation, and deamination. Evaluation of 18 antibiotics’ removal in reclaimed water showed cometabolism decreased the total concentrations of these antibiotics from 495.54 ng L−1 to 221.80 ng L−1. Our findings not only highlight the application potential of cometabolism in increasing engineering feasibility of microalgal degradation of antibiotics from wastewaters, but also provide the unique insights into unraveling the “black-box” of cometabolisms in aerobic biodegradation.
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•Toxicological effects of ciprofloxacin on C. mexicana was studied.•96h EC50 of ciprofloxacin for C. mexicana was 65mgL−1.•Ciprofloxacin influenced the biochemical characteristics of ...microalgal cells.•MDA and SOD of C. mexicana were significantly increased by ciprofloxacin.•Sodium acetate acts as an electron donor and enhanced ciprofloxacin removal.
This study evaluated the toxicity and cellular stresses of ciprofloxacin (CIP) and its co-metabolic removal in a freshwater microalga Chlamydomonas mexicana. The toxicological effects of CIP on C. mexicana were assessed by studying the growth and biochemical characteristics of the microalga including total chlorophyll, carotenoid content, malondialdehyde (MDA) and superoxide dismutase (SOD) activity. The calculated effective concentration (EC50) of CIP on C. mexicana was 65±4mgL−1 at 96h. The growth of C. mexicana was significantly inhibited at increased concentrations of CIP, showing 36±1, 75±3. and 88±3% inhibition at 40, 60 and 100mgL−1 CIP, respectively, compared to the control after 11days of cultivation. The total chlorophyll, carotenoid, MDA and SOD activity were significantly increased as a result of relatively high concentrations of CIP stress. C. mexicana showed 13±1% removal of CIP (2mgL−1) after 11days of cultivation; however, the addition of an electron donor (sodium acetate, 4gL−1) highly enhanced the removal of CIP (2mgL−1) by>3-fold after 11days. Kinetic studies showed that removal of CIP followed a first-order model (R2 0.94–0.97) with the apparent rate constants (k) ranging from 0.0121 to 0.079 d−1.
Enrofloxacin (ENR), a fluoroquinolone antibiotic, has gained big scientific concern due to its ecotoxicity on aquatic microbiota. The ecotoxicity and removal of ENR by five individual microalgae ...species and their consortium were studied to correlate the behavior and interaction of ENR in natural systems. The individual microalgal species (Scenedesmus obliquus, Chlamydomonas mexicana, Chlorella vulgaris, Ourococcus multisporus, Micractinium resseri) and their consortium could withstand high doses of ENR (≤1 mg L-1). Growth inhibition (68–81%) of the individual microalgae species and their consortium was observed in ENR (100 mg L-1) compared to control after 11 days of cultivation. The calculated 96 h EC50 of ENR for individual microalgae species and microalgae consortium was 9.6–15.0 mg ENR L−1. All the microalgae could recover from the toxicity of high concentrations of ENR during cultivation. The biochemical characteristics (total chlorophyll, carotenoid, and malondialdehyde) were significantly influenced by ENR (1–100 mg L-1) stress. The individual microalgae species and microalgae consortium removed 18–26% ENR at day 11. Although the microalgae consortium showed a higher sensitivity (with lower EC50) toward ENR than the individual microalgae species, the removal efficiency of ENR by the constructed microalgae consortium was comparable to that of the most effective microalgal species.
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•Toxicity of enrofloxacin on pure microalgae and microalgae consortium was studied.•Enrofloxacin influenced the biochemical characteristics of microalgae cells.•96 h EC50 of enrofloxacin ranged from 9.6 to 15.0 mg L-1 for microalgae.•Microalgae consortium showed highest sensitivity to enrofloxacin.•Enrofloxacin removal by the consortium was comparable to that of the individual microalgal species.
Detailed studies on the ecotoxicological effects of one emerging contaminant, enrofloxacin and its remediation by microalgae were investigated.
Antibiotic contamination in the environment has significant adverse effects on benthic microorganisms, which causes dysfunction of normal ecological processes. However, in-depth molecular mechanisms ...underlying the potential ecological impacts of these emerging pollutants are poorly understood. In this study, metabolic perturbations in a freshwater microalga, Desmodesmus quadricauda by sulfacetamide (SFM) were investigated using transcriptomics. The results found 28 genes in the tricarboxylic acid cycle and oxidative phosphorolysis pathways were significantly downregulated by 3.97 to 6.07, and 2.47 to 5.99 folds by 0.1 and 1 mg L−1 SFM, respectively. These results indicated that SFM disrupted the microalgal cellular activities through inhibition of energy metabolism. Whilst, the upregulated genes have been most enriched in porphyrin and chlorophyll metabolism (hemE, hemL, hemY, chlD, chlP, PAO, and CAO), and arachidonic acid metabolism (GGT1_5 and gpx). Expression of these genes was significantly upregulated by up to 3.36 times for tolerance against SFM. Moreover, the genes encoding decarboxylase, oxidoreductases, α-amylase, hydrolases, O-acetyltransferase, and lyase were upregulated by >2 folds, which can induce di/hydroxylation, decarboxylation, bond cleavage and deamination. These findings provide insights into the molecular mechanisms of the ecotoxicological effects of antibiotics on microalgae, and supply useful information for their environmental risk assessment and management.
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•Transcriptomics unraveled metabolic perturbations of Desmodesmus quadricauda by sulfacetamide.•Key genes involved in multiple defense and degradation systems were shown.•Tricarboxylic acid cycle and oxidative phosphorolysis were mainly disrupted.•Porphyrin and chlorophyll, and arachidonic acid metabolism were most enriched pathways.
A comprehensive ecotoxicological evaluation of a sulfamethazine (SMZ) and sulfamethoxazole (SMX) mixture was conducted using an indicator microalga, Scenedesmus obliquus. The toxicological effects of ...this mixture were studied using microalgal growth patterns, biochemical characteristics (total chlorophyll, carotenoid, carbohydrate, fatty acid methyl ester), and elemental and Fourier-transform infrared spectroscopy analyses. The 96-h half maximal effective concentration (EC50) of the SMZ and SMX mixture was calculated to be 0.15 mg L−1 according to the dose-response curves obtained. The chlorophyll content decreased with elevated SMZ and SMX concentrations, while the carotenoid content initially increased and then decreased as concentration raised. The unsaturated fatty acid methyl esters (FAMEs) content was enhanced with higher SMZ and SMX concentrations, while that of saturated FAMEs simultaneously decreased due to SMZ and SMX stress. Elemental analyses showed an improved percentage of nitrogen and sulfur in the microalgal biomass as SMZ and SMX concentrations increased. The microalga S. obliquus was shown to biodegrade the chemicals tested and removed 31.4–62.3% of the 0.025–0.25 mg SMZ L−1 and 27.7–46.8% of the 0.025–0.25 mg SMX L−1 in the mixture after 12 days of cultivation. The greater biodegradation observed at higher SMZ and SMX concentrations indicates that microalgal degradation of SMZ and SMX could act as an efficient adaptive mechanism to antibiotics.
•S. obliquus can withstand high doses of SMZ and SMX.•EC50 of SMZ, SMX and their mixture for S. obliquus was 1.23, 0.12, and 0.15 mg L−1.•S. obliquus removed 62.3 and 46.8% of SMZ and SMX, respectively.•A greater biodegradation was observed in higher SMZ and SMX concentration.
Addition of phytohormones (diethyl aminoethyl hexanoate and indole acetic acid) at 10−5 M significantly increased the growth of a green microalga, Chlorella pyrenoidosa up to 62.25% achieving cell ...concentrations of 5.13╳107 cells ml−1. Yielding of high-value added byproducts (pigments, carbohydrate, proteins, and fatty acids) was more in presence of phytohormones comparing to the control. Further transcriptomics analysis demonstrated phytohormones upregulated numerous genes involved in DNA replication and repair pathways, and energy metabolisms (glycolysis, citrate cycle, and oxidative phosphorylation). Moreover, genes in purine metabolism, and porphyrin and chlorophyll metabolism were also more expressed by up to 6.49 times with phytohormones. These pathways can supply more cellular signaling molecules and antioxidant contents. This study carried new insights on the key driving factors in phytohormone enhanced microalgal biomass production processes, which can help to find more feasible application solutions of phytohormones in microalgal biofactories.
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•Microalgal biomass production was enhanced by 62.25% under phytohormones.•High-value added byproducts yields more with addition of phytohormones.•Improved DNA replication and repair processes helped to more cells' production.•Genes involved in energy metabolism were significantly upregulated with phytohormones.
Reclaimed water (RW) has been extensively used for irrigation in agriculture, yet the occurrence of antibiotics in real RW, and their toxicity, uptake dynamics and metabolic fate still needs ...comprehensive exploration. In this study, we investigated the residual concentrations of nineteen antibiotics in the RW from four wastewater treatment plants, and determined their toxicity on plant at environment-relevant concentration. Total found concentrations of these antibiotics ranged from 623.66 ng L−1 to 1536.96 ng L−1, which decreased 10.3 and 19.4 % of roots' length and weight. Uptake dynamics analysis of the most hazardous antibiotic, norfloxacin (NFX) showed increasing amounts in the roots and leaves up to 3087.71 μg g−1. Ryegrass also can remove >80 % of 100 μg L−1 NFX being achieved by biodegradation through ring cleavage, decarboxylation, defluorination, hydrogenation, methylation and oxidation. Toxicity assessment of the identified byproducts showed their more toxic effect on fish, daphnia and algae. This study extended our understanding of the fate of antibiotics in plants during irrigation with reclaimed water, and emphasized its safety and pollutants' biomagnification concerns.
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•Totally residual concentrations of antibiotics in four different reclaimed water were up to 1536.96 ng L-1.•Lolium perenne L. showed efficient removal (>80%) of fluoroquinolone and sulfonamide antibiotics.•Antibiotic mixture at environment-relevant concentration significantly disrupted the development of plants.•Bioaccumulated norfloxacin (the most hazardous antibiotic) in leaves and roots can reach 3087.71 μg g-1.•Rng cleavage, decarboxylation, defluorination, hydrogenation, methylation and oxidation of norfloxacin were proposed for its degradation.
