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1.
Ecotoxicology ; 28(7): 834-842, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31352571

RESUMO

Although microcystins (MCs) are the most commonly studied cyanotoxins, their significance to the producing organisms remains unclear. MCs are known as endotoxins, but they can be found in the surrounding environment due to cell lysis, designated as extracellular MCs. In the present study, the interactions between MC producing and the non-producing strains of Microcystis aeruginosa, PCC 7806 and PCC 7005, respectively, and a green alga, Desmodesmus subspicatus, were studied to better understand the probable ecological importance of MCs at the collapse phase of cyanobacterial blooms. We applied a dialysis co-cultivation system where M. aeruginosa was grown inside dialysis tubing for one month. Then, D. subspicatus was added to the culture system on the outside of the membrane. Consequently, the growth of D. subspicatus and MC contents were measured over a 14-day co-exposure period. The results showed that Microcystis negatively affected the green alga as the growth of D. subspicatus was significantly inhibited in co-cultivation with both the MC-producing and -deficient strains. However, the inhibitory effect of the MC-producing strain was greater and observed earlier compared to the MC-deficient strain. Thus, MCs might be considered as an assistant factor that, in combination with other secondary metabolites of Microcystis, reinforce the ability to outcompete co-existing species.


Assuntos
Clorófitas/efeitos dos fármacos , Microcistinas/efeitos adversos , Microcystis/química , Clorófitas/crescimento & desenvolvimento , Eutrofização
2.
World J Microbiol Biotechnol ; 35(7): 110, 2019 Jul 06.
Artigo em Inglês | MEDLINE | ID: mdl-31280381

RESUMO

Carbon sources whether types or magnitudes were fateful in terms of stimulating growth and lipids accumulation in microalgae applied for biodiesel production. The set scenario of this work was to investigate the feasibilities of glucose (G) combining with sodium acetate (SA) carbon sources in enhancing biomass and lipid accumulation in Coccomyxa subellipsoidea. The results demonstrated that C. subellipsoidea subjected to the combination feeding of G (20 g/L) and SA (12 g/L) achieved the favorable biomass (5.22 g/L) and lipid content (52.16%). The resulting lipid productivity (388.96 mg/L/day) was 1.33- to 7.60-fold more than those of sole G or SA as well as other combinations of G and SA. Even though the total fatty acids of C. subellipsoidea cells treated with the optimal combination of G and SA showed no noticeable increment in comparison with sole G or SA, the proportion of monounsaturated C18:1 (over 48.69%) and the content of C18:3 (< 12%) were commendable in high-quality algal biodiesel production. Further, such fascinating lipid accumulation in C. subellipsoidea cells treated with G combining with SA might be attributed to that G promoted glycolysis as well as SA activated glyoxylate shunt and TCA cycle to synergistically provide sufficient acetyl-CoA precursors for lipid accumulation. These findings hinted the potential of the combination of carbon sources in enhancing the overall lipid productivity to offset alga-based biodiesel production cost and would guide other alga strains cultivation.


Assuntos
Clorófitas/crescimento & desenvolvimento , Clorófitas/metabolismo , Glucose/metabolismo , Lipídeos/biossíntese , Acetato de Sódio/metabolismo , Biocombustíveis , Biomassa , Carbono/metabolismo , Clorófitas/citologia , Meios de Cultura/química , Ácidos Graxos/biossíntese , Metabolômica , Microalgas/crescimento & desenvolvimento , Microalgas/metabolismo , Nitrogênio/metabolismo
3.
Environ Sci Pollut Res Int ; 26(19): 19335-19351, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31073833

RESUMO

Lithium is registered as a serious pollutant that causes environmental damage to an irrigation water supply. Freshwater green alga (Oocystis solitaria) was studied for its potential to remove lithium ions from aqueous solutions. The Plackett-Burman design was applied for initial screening of six factors for their significances for the removal of lithium from aqueous solutions using Oocystis solitaria cells. Among the variables screened, pH, lithium concentration, and temperature were the most significant factors affecting lithium removal. Hence, the levels of these significant variables were further investigated for their interaction effects on lithium removal using the Box-Behnken statistical design. The optimum conditions for maximum lithium removal from aqueous solutions by Oocystis solitaria were the initial lithium concentration of 200 mg/L, contact time of 60 min, temperature of 30 °C, pH 5, and biomass of Oocystis solitaria cells of 1 g/L with agitation condition. Under the optimized conditions, the percentage of maximum lithium removal was 99.95% which is larger than the percentage of lithium removal recorded before applying the Plackett-Burman design (40.07%) by 2.49 times. The different properties of Oocystis solitaria, as an adsorbent, were explored with SEM and via FTIR analysis. The spectrum of FTIR analysis for samples of Oocystis solitaria cells before lithium biosorption showed different absorption peaks at 3394 cm-1, 2068 cm-1, 1638 cm-1, 1398 cm-1, 1071 cm-1, and 649 cm-1 which has been shifted to 3446 cm-1, 2924 cm-1, 1638 cm-1, 1384 cm-1, 1032 cm-1, and 613 cm-1, respectively, after lithium biosorption by the alga. The treatment of aqueous solution containing lithium with Oocystis solitaria cells immobilized in alginate beads removed 98.71% of lithium at an initial concentration of 200 mg/L after 5 h. Therefore, Oocystis solitaria may be considered as an alternative for sorption and removal of lithium ions from wastewaters.


Assuntos
Clorófitas/crescimento & desenvolvimento , Água Doce/química , Lítio/análise , Modelos Teóricos , Poluentes Químicos da Água/análise , Adsorção , Biodegradação Ambiental , Biomassa , Concentração de Íons de Hidrogênio , Soluções , Temperatura Ambiente
4.
Chemosphere ; 228: 503-512, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31051353

RESUMO

Hydrogen peroxide (HP) is a feasible algicide to control cyanobacterial blooms, but its application in the waters with strong reductive power is still a problem. The rapid decomposition rate of HP results in a short residence time in the waters, which renders the failure of bloom mitigation. In this study, the damage of Microcystis aeruginosa (M. aeruginosa) by HP, the optimization method for Microcystis bloom control and its field effects were investigated. Results of microcosm experiments indicated M. aeruginosa was vulnerable to HP. The HP-induced damage was mainly attributed to the impairments of HP detoxification pathways and photosystem. Repetitive additions of HP, which could prolong the residence time, were conducted in the mesocosm experiments. HP concentration ranged from 96 µM to 165 µM for 2 h could successfully mitigate Microcystis bloom, even though HP decomposition rate reached 109 µM per h. Besides the removal of M. aeruginosa, contents of total dissolved nitrogen, total dissolved phosphate, dissolved organic carbon and chromophoric dissolved organic matter in water column increased significantly (p < 0.05). The enrichment of nutrients promoted the growth of chlorophytes but the growth of M. aeruginosa couldn't be observed. The dominant species thrived in the HP-treated waters was Chlamydomonas sp. Results in this study confirmed that HP was a promising algicide for cyanobacterial blooms control. The optimization method further demonstrated that repetitive additions of HP could favor the mitigation of cyanobacterial blooms.


Assuntos
Clorófitas/crescimento & desenvolvimento , Peróxido de Hidrogênio/química , Microcystis/química
5.
Extremophiles ; 23(4): 467-477, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31087168

RESUMO

In April 2014, dual bloom of green algae and purple bacteria occurred in a shallow, alkaline soda pan (Kiskunság National Park, Hungary). The water was only 5 cm deep, in which an upper green layer was clearly separated from a near-sediment purple one. Based on microscopy and DNA-based identification, the upper was inhabited by a dense population of the planktonic green alga, Oocystis submarina Lagerheim, while the deeper layer was formed by purple, bacteriochlorophyll-containing bacteria, predominated by Thiorhodospira and Rhodobaca. Additional bacterial taxa with a presumed capability of anoxygenic phototrophic growth belonged to the genera Loktanella and Porphyrobacter. Comparing the bacterial community of the purple layer with a former blooming event in a nearby soda pan, similar functional but different taxonomic composition was revealed. Members from many dominant bacterial groups were successfully cultivated including potentially new species, which could be the result of the application of newly designed media.


Assuntos
Clorófitas/crescimento & desenvolvimento , Eutrofização , Lagos/microbiologia , Microbiota , Proteobactérias/crescimento & desenvolvimento , Biomassa , Fitoplâncton/crescimento & desenvolvimento
6.
PLoS One ; 14(5): e0216755, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31107886

RESUMO

Astaxanthin is a highly potent antioxidant which can be extracted from Haematococcus pluvialis when cultivated and induced at high stress conditions. Due to astaxanthin's hydrophobicity, methoxypolyethylene glycol-polycaprolactone (mPEG-PCL) copolymer was synthesized to form polymeric micelles for the encapsulation of astaxanthin. Astaxanthin-loaded polymeric micelles were then used to examine the effects on the proliferation and differentiation of human mesenchymal stem cells (MSCs). Dynamic light scattering (DLS) and Fourier transform infrared spectroscopy (FT-IR) confirmed astaxanthin was encapsulated into mPEG-PCL micelles. Astaxanthin loading and encapsulation efficiency, determined by UV/Vis spectroscopy, were 3.27% and 96.67%, respectively. After 48 h, a total of 87.31% of astaxanthin was released from the polymeric micelles. The drug release profile was better fit by the Michaelis-Menten type model than the power law model. The MSC culture results showed that culture medium supplemented with 0.5 µg/mL astaxanthin-encapsulated polymeric micelles led to a 26.3% increase in MSC proliferation over an 8-day culture period. MSC differentiation results showed that 20 ng/mL astaxanthin-encapsulated polymeric micelles enhanced adipogenesis, chondrogenesis, and osteogenesis of MSCs by 52%, 106%, and 182%, respectively.


Assuntos
Células-Tronco Mesenquimais/citologia , Células-Tronco Mesenquimais/efeitos dos fármacos , Adipócitos/citologia , Adipócitos/efeitos dos fármacos , Antioxidantes/administração & dosagem , Antioxidantes/isolamento & purificação , Diferenciação Celular/efeitos dos fármacos , Proliferação de Células/efeitos dos fármacos , Células Cultivadas , Clorófitas/crescimento & desenvolvimento , Clorófitas/metabolismo , Condrócitos/citologia , Condrócitos/efeitos dos fármacos , Portadores de Fármacos/química , Liberação Controlada de Fármacos , Humanos , Micelas , Nanocápsulas/química , Osteoblastos/citologia , Osteoblastos/efeitos dos fármacos , Poliésteres , Polietilenoglicóis , Solubilidade , Xantofilas/administração & dosagem , Xantofilas/isolamento & purificação
7.
Mar Drugs ; 17(6)2019 May 28.
Artigo em Inglês | MEDLINE | ID: mdl-31142027

RESUMO

Recent studies have shown that marine algae represent a great source of natural compounds with several properties. The lipidic extract of the seaweed Chaetomorpha linum (Chlorophyta, Cladophorales), one of the dominant species in the Mar Piccolo of Taranto (Mediterranean, Ionian Sea), revealed an antibacterial activity against Vibrio ordalii and Vibrio vulnificus, common pathogens in aquaculture, suggesting its potential employment to control fish and shellfish diseases due to vibriosis and to reduce the public health hazards related to antibiotic use in aquaculture. This extract showed also an antioxidant activity, corresponding to 170.960 ± 16. mmol Trolox equivalent/g (oxygen radical absorbance capacity assay-ORAC) and to 30.554 ± 2.30 mmol Trolox equivalent/g (Trolox equivalent antioxidant capacity assay-TEAC). The chemical characterization of the extract, performed by 1D and 2D NMR spectroscopy, highlighted the presence of free, saturated (SAFAs), unsaturated (UFAs) and polyunsaturated (PUFAs) fatty acids. The high content of ω-6 and ω-3 PUFAs confirmed also by gas chromatography indicates the potentiality of this algal species in the production of fortified food. The antibacterial activity seems related to the presence of linolenic acid present at high density, while the antioxidant activity could be likely ascribable to molecules such as carotenoids and chlorophylls (characterized also by thin-layer chromatography), known for this property. The presence of polyhydroxybutyrate, a biopolymer with potentiality in the field of biodegradable bioplastics was also detected. The exploitation of C. linum for a future biotechnological application is also encouraged by the results from a first attempt of cultivating this species in an integrated multi-trophic aquaculture (IMTA) system.


Assuntos
Clorófitas/química , Lipídeos/química , Lipídeos/farmacologia , Compostos Fitoquímicos/química , Antibacterianos/química , Antibacterianos/farmacologia , Antioxidantes/química , Antioxidantes/farmacologia , Bactérias/efeitos dos fármacos , Clorófitas/crescimento & desenvolvimento , Cromatografia em Camada Delgada , Ácidos Graxos/análise , Espectroscopia de Ressonância Magnética , Mar Mediterrâneo , Compostos Fitoquímicos/farmacologia , Pigmentos Biológicos/química
8.
Genes (Basel) ; 10(5)2019 05 26.
Artigo em Inglês | MEDLINE | ID: mdl-31130696

RESUMO

Ostreococcustauri is an easily cultured representative of unicellular algae (class Mamiellophyceae) that abound in oceans worldwide. Eight complete 13-22 Mb genomes of phylogenetically divergent species within this class are available, and their DNA sequences are nearly always present in metagenomic data produced from marine samples. Here we describe a simplified and robust transformation protocol for the smallest of these algae (O. tauri). Polyethylene glycol (PEG) treatment was much more efficient than the previously described electroporation protocol. Short (2 min or less) incubation times in PEG gave >104 transformants per microgram DNA. The time of cell recovery after transformation could be reduced to a few hours, permitting the experiment to be done in a day rather than overnight as used in previous protocols. DNA was randomly inserted in the O. tauri genome. In our hands PEG was 20-40-fold more efficient than electroporation for the transformation of O. tauri, and this improvement will facilitate mutagenesis of all of the dispensable genes present in the tiny O. tauri genome.


Assuntos
Clorófitas/genética , Variação Genética , Transformação Genética/genética , Sequência de Bases , Clorófitas/efeitos dos fármacos , Clorófitas/crescimento & desenvolvimento , Genoma/genética , Filogenia , Polietilenoglicóis/farmacologia , Transformação Genética/efeitos dos fármacos
9.
Ecotoxicol Environ Saf ; 180: 430-438, 2019 Sep 30.
Artigo em Inglês | MEDLINE | ID: mdl-31112842

RESUMO

The potential of Dunaliella salina isolated from Sambhar Salt Lake (Rajasthan, India) for biosorption of hexavalent chromium Cr(VI) in aqueous solution has been examined under optimized culture conditions. The influence of various process parameters, such as pH (6-11), incubation time (48-120 h), metal concentration (5-25 mgL-1), inoculum dose (2-10% vv-1), and their combination effects during Cr(VI) sorbtion were analyzed by means of Response Surface Methodology (RSM) based on a 3-level Box-Behnken experiment design. Microalgae showed highest chromium biosorption with 66.4% efficiency at optimum pH (8.6) and 10% (vv-1) inoculum size within 120 h. The experimental data obtained were analyzed by analysis of variance (ANOVA) along with lower value of coefficient of variation (34%), indicated the well fitness of quadratic equation as proposed by response surface model. Involvement of the surface morphology of the microalgae biomass and elemental distribution was studied through Scanning Electron Microscope (SEM), Energy Dispersive X-ray Spectroscopic (EDS), Fourier-transform infrared spectroscopy (FTIR) and X-ray Diffraction (XRD) analysis. The findings unequivocally corroborates that the novel microalgae inherits immense potential in alleviating the levels of toxic heavy metal, such as Cr(VI) from the hydrosphere at wide range of pH and metal concentrations. The present study provides a workable solution for bioremediation of hazardous heavy metals, in general, and Cr(VI) in specific from the industrial wastes like tannery effluents.


Assuntos
Clorófitas/crescimento & desenvolvimento , Cromo/análise , Lagos/química , Poluentes Químicos da Água/análise , Adsorção , Biodegradação Ambiental , Clorófitas/química , Concentração de Íons de Hidrogênio , Índia , Resíduos Industriais/análise , Modelos Teóricos
10.
Artigo em Inglês | MEDLINE | ID: mdl-30987041

RESUMO

In order to study the effects of nitrogen stress on the lipid synthesis of Parachlorella kessleri TY02 and to understand the changes in growth, photosynthetic pigments, total protein and total carbohydrate contents during lipid accumulation, the cells of the strain were cultured in nitrogen-deficient (N-) and nitrogen-rich (N⁺) media for one week. Changes in cell growth, chlorophyll content, chlorophyll fluorescence parameters, neutral lipid and total lipid content, total protein content and total carbohydrate content were measured and analyzed. The results showed that, under nitrogen stress, the algal strain grew slowly, and chlorophyll and total protein contents decreased, while total carbohydrate and total lipid contents increased. This indicated that, under nitrogen stress, most of the carbon flowed to the synthesis of lipids and carbohydrates. Meanwhile, reducing the nitrogen content was a relatively economical and easy to operate method of promoting lipid accumulation.


Assuntos
Clorófitas/fisiologia , Metabolismo dos Lipídeos , Estresse Fisiológico , Carboidratos/análise , Carbono/metabolismo , Clorofila/metabolismo , Clorófitas/crescimento & desenvolvimento , Clorófitas/metabolismo , Nitrogênio/metabolismo , Fotossíntese , Proteínas de Plantas/metabolismo
11.
Opt Express ; 27(4): 4528-4548, 2019 Feb 18.
Artigo em Inglês | MEDLINE | ID: mdl-30876071

RESUMO

Several algorithms have been proposed to detect floating macroalgae blooms in the global ocean. However, some of them are difficult or even impossible to routinely apply by non-experts because of performing a sophisticated atmospheric correction scheme or due to the mismatch in spectral bands from one sensor to another. Here, a generic, simple and effective method, referred to as the Floating Green Tide Index (FGTI), was proposed to detect floating green macroalgae blooms (GMB). The FGTI was defined as the difference between greenness and wetness features extracted from digital number (DN) observation through Tasseled Cap Transformation analysis, providing the advantage of bypassing the atmospheric correction procedure. Through cross-index and cross-sensor comparisons, the FGTI showed similar performance to the existing VB-FAH (Virtual-Baseline Floating macroAlgae Height) and FAI (Floating Algae Index) algorithms but proved more robust than the traditional NDVI (Normalized Difference Vegetation Index) in terms of response to perturbations by environmental conditions, viewing geometry, sun glint, and thin cloud contamination. Given the requirement for spectral bands in the current and planned satellite sensors, the FGTI design can easily be extended to any satellite sensor, and therefore provide an excellent data resource for studying GMB in any part of the global ocean.


Assuntos
Clorófitas/crescimento & desenvolvimento , Monitoramento Ambiental/métodos , Tecnologia de Sensoriamento Remoto , Alga Marinha/crescimento & desenvolvimento , Algoritmos , Clorófitas/química , Oceano Pacífico , Alga Marinha/química , Poluentes da Água/análise
12.
FEMS Microbiol Lett ; 366(5)2019 03 01.
Artigo em Inglês | MEDLINE | ID: mdl-30839066

RESUMO

Dense communities of carotenoid-rich members of the Halobacteria (Euryarchaeota), the bacterium Salinibacter (Bacteroidetes) and the eukaryotic alga Dunaliella color the brines of most saltern crystallizer ponds red. The first report we found from the western world mentioning these red brines dates from 1765: the Encyclopédie of Diderot and coworkers. Earlier descriptions of solar salterns since Roman times do not mention red ponds. These include the Astronomica of Manilius, Pliny's Naturalis Historia (1st century), the description of Italian salterns in De Reditu Suo by Namatianus (5th century), Agricola's De Re Metallica (1556) and an anonymous description of French salterns (1669). This suggests that in earlier times, saltern brines may not have been red. In salterns which are operated today in the traditional way as practiced in the Middle Ages, no red brines are observed. Prokaryotic densities in the salterns of Secovlje (Slovenia) and Ston (Croatia) are an order of magnitude lower than in modern saltern crystallizers. This is probably due to the much shorter residence time of the brine in the traditionally operated salterns. In China, red saltern brines were documented earlier: in Li Shizhen's compendium of Materia Medica Ben Cao Kang Mu, completed in 1578 and based on older sources.


Assuntos
Cloreto de Sódio , Microbiologia da Água , Bacteroidetes/química , Bacteroidetes/crescimento & desenvolvimento , Carotenoides/análise , Clorófitas/química , Clorófitas/crescimento & desenvolvimento , Halobacteriaceae/química , Halobacteriaceae/crescimento & desenvolvimento , História do Século XVI , História do Século XVII , História do Século XVIII , História do Século XXI , Salinidade , Cloreto de Sódio/química , Cloreto de Sódio/história
13.
Chemosphere ; 224: 93-102, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-30818199

RESUMO

In their environments, aquatic organisms are simultaneously exposed to mixtures of several endocrine disrupting compounds, including hormones. However, most of the toxicity studies so far focused on effects of single contaminants. The available information on the potential toxicity of combined hormones on microalgae is extremely limited. For these reasons the aim of this study was to evaluate the individual and mixture effect of estrone (E1), ß-estradiol (E2), estriol (E3), 17-α-ethinylestradiol (EE2), progesterone (PRO), 5-pregnen-3ß-ol-20-one (PRE), levonorgestrel (LG) and testosterone (TST) on Chlorella vulgaris and Scenedesmus armatus. Green algae cells were exposed to different concentrations (0.1-100 mg L-1) of hormones for 14 days. Biomass in the form of dry weight and chlorophyll a was examined. The decreasing order of toxicity (based on EC50, 14d) to Chlorella vulgaris and Scenedesmus armatus was: EE2>PRO > E2>PRE > TST > E3>LG > E1 and EE2>PRO > TST > E2>PRE > LG > E1>E3, respectively. Chlorella vulgaris was more sensitive to the effects of hormones than Scenedesmus armatus. Although mixed hormones were more toxic to green algae than single hormones, in the ecosystem mixtures can pose higher ecological risk than single pollutants. Therefore, data on the toxicology of both single and mixed hormones is very valuable for assessment of the possibility of adverse ecological effects caused by these pollutants. Furthermore, these results suggest that environmental exposure to hormone mixtures may cause toxicity levels different to the sum of those of the single hormones and provides a basic understanding of their toxic effect on algae.


Assuntos
Clorófitas/efeitos dos fármacos , Misturas Complexas/toxicidade , Hormônios/toxicidade , Chlorella vulgaris/efeitos dos fármacos , Chlorella vulgaris/crescimento & desenvolvimento , Clorófitas/crescimento & desenvolvimento , Disruptores Endócrinos/toxicidade , Microalgas/efeitos dos fármacos , Scenedesmus/efeitos dos fármacos , Scenedesmus/crescimento & desenvolvimento , Poluentes Químicos da Água/farmacologia
14.
Ecotoxicol Environ Saf ; 174: 491-497, 2019 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-30856561

RESUMO

Benzalkonium compounds are widely used and found in environmental samples. Due to their amphiphilic nature, it is important to know sorption coefficients to account their bioavailability. However, currently available models describing their partitioning were developed using low molecular weight homologues and it cannot be ascertained whether they are applicable to their higher molecular weight homologues. Reasons for the scarcity of data on highly sorptive compounds include the lack of reliable quantification techniques for analyzing these chemicals at environmentally relevant levels. This study, therefore, reports on an algal growth inhibition assay-based method for the determination of kaolinite/water distribution coefficients for benzalkonium compounds at their environmentally relevant concentration range. Sorption to clay was computed using the difference between median effective concentration determined in a culture with kaolinite and that derived from a culture grown in standard medium. A kinetic model was used to account for uptake into algal cells and to calculate free concentrations. Due to the sensitivity of the algal species, Pseudokirchneriella subcapitata, it was possible to determine distribution coefficients below micromole per liter concentrations. The computed distribution coefficients showed a linear increase with number of carbon atoms in the alkyl chain up to 14. The proposed bioassay-based method should be applicable to determine distribution coefficients for highly hydrophobic chemicals and ionic liquids at a concentration range lower than typical analytical limits.


Assuntos
Compostos de Benzalcônio/análise , Clorófitas/efeitos dos fármacos , Argila/química , Caulim/química , Modelos Teóricos , Água/química , Adsorção , Compostos de Benzalcônio/química , Compostos de Benzalcônio/toxicidade , Bioensaio , Clorófitas/crescimento & desenvolvimento , Interações Hidrofóbicas e Hidrofílicas , Cinética , Propriedades de Superfície
15.
Ecotoxicol Environ Saf ; 174: 584-591, 2019 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-30870659

RESUMO

Single and multispecies algal bioassays were assessed using copper toxicity with three green algae (Scenedesmus subspicatus, Scenedesmus quadricauda and Ankistrodesmus angustus) and one blue-green algae species (Oscillatoria prolifera). Single and multispecies toxicity tests were conducted based on cell density as per standard toxicity testing, and on equivalent surface area. A higher copper sulfate toxicity was registered for O. prolifera, followed by S. subspicatus, S. quadricauda, and A. angustus in single-species toxicity tests based on cell density. Single species toxicity tests based on surface area showed increased copper toxicity with increasing algal surface area except for A. angustus. In multispecies control bioassays, the growth of A. angustus was inhibited in the presence of other species in surface area-based tests. As compared to single species bioassays, O. prolifera, and S. quadricauda showed a decreased sensitivity to copper sulfate in both cell density and surface area based multispecies tests. However, for the algae species with the smallest surface area, S. subspicatus, 96h-EC50 value decreased in multispecies bioassays based on surface area as compared to the single species test, while it increased in multispecies bioassays based on cell density. The difference in S. subspicatus sensitivity to copper between tests based on cell density and surface area supports the need to adopt multispecies toxicity testing based on surface area to avoid the confounding effect on copper toxicity of increased biomass for metal binding. 96h-EC50 values for all species combined in the multispecies test based on cell density and on surface area were significantly different from 96h-EC50 values obtained in single species bioassays. These results demonstrate that single-species bioassays may over- or underestimate metal toxicity in natural waters.


Assuntos
Clorófitas/efeitos dos fármacos , Sulfato de Cobre/toxicidade , Herbicidas/toxicidade , Bioensaio , Contagem de Células , Clorófitas/citologia , Clorófitas/crescimento & desenvolvimento , Cianobactérias/citologia , Cianobactérias/efeitos dos fármacos , Cianobactérias/crescimento & desenvolvimento , Scenedesmus/citologia , Scenedesmus/efeitos dos fármacos , Scenedesmus/crescimento & desenvolvimento , Testes de Toxicidade
16.
Aquat Toxicol ; 210: 179-187, 2019 May.
Artigo em Inglês | MEDLINE | ID: mdl-30870664

RESUMO

Nanoplastics are recognized as able to interact with other pollutants including heavy metals, and with natural organic matter, with implications for the potential risks to biota. We investigated the interaction of carboxylated polystyrene nanoparticles (PS-COOH NPs) with copper (Cu) and algal exudates (EPS) and how such interaction could affect Cu toxicity towards the freshwater microalga Raphidocelis subcapitata. PS-COOH NPs behavior in the presence of Cu and EPS was determined by dynamic light scattering (DLS), while PS-COOH NPs surface interaction with Cu ions and EPS was investigated by fluorimetric analysis. ICP-MS was used to test Cu ion adsorption to PS-COOH NPs in the presence and absence of algae. The interaction between PS-COOH NPs and the algal cell wall was assessed by fluorescence microscopy. Short- and long-term toxicity tests were carried out in parallel to assess the impact of PS-COOH NPs on algal growth. Results showed altered nanoparticle surface charge and hydrodynamic diameter following algal EPS exposure, supporting the hypothesis of a protein corona formation. In contrast, no absorption of Cu ions was observed on PS-COOH NPs, either in the presence or absence of algae. No differences on algal growth inhibition were observed between exposure to Cu only, and to Cu in combination with PS-COOH NPs, in short-term as well as long-term tests. However, after 72 h of exposure, the adsorption of PS-COOH NPs to algal cell walls appeared to correspond to morphological alterations, revealing potential disturbances in the mitotic cycle. Our findings confirm the ability of PS-COOH NPs to interact with EPS as shown for other nanomaterials. Environmentally realistic exposure scenarios are thus needed for evaluating nanoplastic toxicity, as nanoparticles will not maintain their pristine nature once released into natural media. Prolonged exposure and use of different end-points such as cell morphological changes and EPS production seem more reliable for the investigation of nanoplastic/algal cell interactions which can drive food chain transfer of nanoplastics and ultimately toxicity.


Assuntos
Clorófitas/efeitos dos fármacos , Cobre/toxicidade , Água Doce/química , Nanopartículas/toxicidade , Poliestirenos/toxicidade , Poluentes Químicos da Água/toxicidade , Clorófitas/crescimento & desenvolvimento , Cobre/química , Cadeia Alimentar , Nanopartículas/química , Poliestirenos/química , Fatores de Tempo , Testes de Toxicidade , Poluentes Químicos da Água/química
17.
Bioresour Technol ; 282: 245-253, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-30870690

RESUMO

Current research aimed to increase mixotrophic biomass from various organic carbon sources by exploring best light conditions. Three substrates glucose, acetic acid and glycerol were studied for their effects on mixotrophic microalgae cultivation under four light conditions. Light irradiance exhibited variability in growth response and photosynthetic efficiency based on type of substrates used in mixotrophic growth. Each substrate showed variability in light requirements for their effective assimilations. From growth responses, glucose and acetic acid respectively exhibited heterotrophic and mixotrophic (better growth in light) natures. Continuous light-deficient condition was adequate for effective mixotrophic growth as well as energy saving for glucose. However, light-sufficient condition required for effective acetic acid supported mixotrophic growth. Mixotrophic benefits from glycerol and its uptake by Chlorella protothecoides was negligible in all light conditions. Investigation of heterotrophic biomass contribution by various substrates in overall mixotrophic yield, glucose offered maximum approx. 43% contribution.


Assuntos
Clorófitas/metabolismo , Microalgas/metabolismo , Biomassa , Chlorella/crescimento & desenvolvimento , Chlorella/metabolismo , Chlorella/efeitos da radiação , Clorófitas/crescimento & desenvolvimento , Clorófitas/efeitos da radiação , Glucose/biossíntese , Processos Heterotróficos , Microalgas/crescimento & desenvolvimento , Microalgas/efeitos da radiação , Fotossíntese
18.
Appl Biochem Biotechnol ; 188(3): 836-853, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-30707345

RESUMO

The growth performance of Chlorella protothecoides, Chlorella pyrenoidosa, and Chlorella sp. in autotrophic cultivation with 10% carbon dioxide (CO2) was evaluated. The biomass production of C. protothecoides, along with its carbon, nitrogen (N), and phosphorus (P) utilization, in batch and semicontinuous autotrophic cultivation with 20% CO2 was also determined. Among the three algae species, C. protothecoides obtained the highest biomass yield (1.08 g/L) and P assimilation (99.4%). Compared with the CO2 flow rate and inoculation ratio in batch cultivation, light intensity considerably improved biomass yield, N and P assimilation, and CO2 utilization. In the semicontinuous cultivation of C. protothecoides, a hydraulic retention time (HRT) of 8 days kept the system at a stable running state, thereby demonstrating that an HRT of 8 days was better than an HRT of 5 days. Among the three N/P ratios for C. protothecoides in semicontinuous cultivation with 20% CO2, 2:1 provided the highest biomass productivity (0.19 g/L/day) and CO2 fixation rate (0.37 g/L/day). Therefore, this lower N/P ratio is more suitable than 10:1 and 50:1 for the growth of C. protothecoides with 20% CO2. Compared with the batch cultivation of C. protothecoides, semicontinuous cultivation improved the CO2 fixation rate (by 1.5-2 times) and CO2 utilization efficiency (by 3-6 times) of C. protothecoides.


Assuntos
Processos Autotróficos , Dióxido de Carbono/metabolismo , Clorófitas/crescimento & desenvolvimento , Clorófitas/metabolismo , Nitrogênio/metabolismo , Fósforo/metabolismo , Biomassa , Clorófitas/efeitos da radiação , Concentração de Íons de Hidrogênio , Luz
19.
Microb Ecol ; 78(3): 603-617, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-30729265

RESUMO

Lake Dziani Dzaha (Mayotte Island, Indian Ocean) is a tropical thalassohaline lake which geochemical and biological conditions make it a unique aquatic ecosystem considered as a modern analogue of Precambrian environments. In the present study, we focused on the diversity of phytoplanktonic communities, which produce very high and stable biomass (mean2014-2015 = 652 ± 179 µg chlorophyll a L-1). As predicted by classical community ecology paradigms, and as observed in similar environments, a single species is expected to dominate the phytoplanktonic communities. To test this hypothesis, we sampled water column in the deepest part of the lake (18 m) during rainy and dry seasons for two consecutive years. Phytoplanktonic communities were characterized using a combination of metagenomic, microscopy-based and flow cytometry approaches, and we used statistical modeling to identify the environmental factors determining the abundance of dominant organisms. As hypothesized, the overall diversity of the phytoplanktonic communities was very low (15 OTUs), but we observed a co-dominance of two, and not only one, OTUs, viz., Arthrospira fusiformis (Cyanobacteria) and Picocystis salinarum (Chlorophyta). We observed a decrease in the abundance of these co-dominant taxa along the depth profile and identified the adverse environmental factors driving this decline. The functional traits measured on isolated strains of these two taxa (i.e., size, pigment composition, and concentration) are then compared and discussed to explain their capacity to cope with the extreme environmental conditions encountered in the aphotic, anoxic, and sulfidic layers of the water column of Lake Dziani Dzaha.


Assuntos
Clorófitas/crescimento & desenvolvimento , Lagos/microbiologia , Fitoplâncton/crescimento & desenvolvimento , Spirulina/crescimento & desenvolvimento , Biodiversidade , Biomassa , Clorofila A/metabolismo , Clorófitas/metabolismo , Ecossistema , Oceano Índico , Ilhas , Fitoplâncton/genética , Estações do Ano , Spirulina/metabolismo
20.
Sci Total Environ ; 653: 1377-1394, 2019 Feb 25.
Artigo em Inglês | MEDLINE | ID: mdl-30759577

RESUMO

The feasibility of generating a lipid-containing algal-bacterial polyculture biomass in municipal primary wastewater and enhancing biomethanation of lipid-extracted algal residues (LEA) through hydrothermal pretreatment and co-digestion with sewage sludge (SS) was investigated. In high-rate algal ponds, the polyculture of native algal and bacteria species demonstrated a monthly average net and gross biomass productivity of 30 ±â€¯3 and 36 ±â€¯3 gAFDW m-2 day-1 (summer season). The algal community was dominated by Micractinium sp. followed by Scenedesmus sp., Chlorella sp., pennate diatoms and Chlamydomonas sp. The polyculture metabolic activities resulted in average reductions of wastewater volatile suspended solids (VSS), carbonaceous soluble biochemical oxygen demand (csBOD5) and total nitrogen (Ntotal) of 63 ±â€¯18%, 98 ±â€¯1% and 76 ±â€¯21%, respectively. Harvested biomass contained nearly 23% lipid content and an extracted blend of fatty acid methyl esters satisfied the ASTM D6751 standard for biodiesel. Anaerobic digestion of lipid extracted algal residues (LEA) demonstrated long lag-phase in methane production of 17 days and ultimate methane yield of 296 ±â€¯2 mL/gVS (or ~50% of theoretical), likely because to its limited biodegradability and toxicity due to presence of the residual solvent (hexane). Hydrothermal pretreatment increased the ultimate methane yield and production rate by 15-30% but did not mitigate solvent toxicity effects completely leading to less substantial improvement in energy output of 5-20% and diminished Net Energy Ratio (NER < 1). In contrast, co-digestion of LEA with sewage sludge (10% to 90% ratio) was found to minimize solvent toxicity and improve methane yield enhancing the energy output ~4-fold, compared to using LEA as a single substrate, and advancing NER to 4.2.


Assuntos
Metano/análise , Águas Residuárias/química , Bactérias/crescimento & desenvolvimento , Biomassa , Clorófitas/química , Clorófitas/crescimento & desenvolvimento , Técnicas de Cocultura , Cinética , Lipídeos/química , Metano/química , Metano/metabolismo , Esgotos/química , Esgotos/microbiologia , Solventes/química , Solventes/toxicidade , Águas Residuárias/microbiologia
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