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1.
Ecotoxicol Environ Saf ; 221: 112468, 2021 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-34198191

RESUMO

The study shows how microalgae biofilm formation and antioxidant responses to the production of reactive oxygen species (ROS) is alter by the presences of Lemna minor L., Chlorella vulgaris, and Aphanizomenon flos-aquae. The study involves the cultivation of the biofilm of Chlorella vulgaris and Aphanizomenon flos-aquae in three bioreactors. The condition of growth for the biofilm formation was varied across the three bioreactors to enable the dominance Chlorella vulgaris and Aphanizomenon flos-aquae in one of the bioreactors. Lemna minor L. was also introduce into one of the bioreactors to determine its effect on the biofilm formation. The result obtained shows that C. vulgaris and A. flos-aquae dominate the biofilm, resulting in a high level of H2O2 and O2- (H2O2 was 0.122 ± 0.052 and 0.183 ± 0.108 mmol/L in C. vulgaris and A. flos-aquae, respectively, and O2- was 0.261 ± 0.039 and 0.251 ± 0.148 mmol/L in C. vulgaris and A. flos-aquae, respectively). The study also revealed that the presence of L. minor L. tend to reduce the oxidative stress to the biofilm leading to low production of ROS (H2O2 was 0.086 ± 0.027 and 0.089 ± 0.045 mmol/L in C. vulgaris and A. flos-aquae respectively, and O2- was 0.185 ± 0.044 and 0.161 ± 0.065 mmol/L in C. vulgaris and A. flos-aquae respectively). The variation in the ability of the biofilm of C. vulgaris and A. flos-aquae to respond via chlorophyll, carotenoid, flavonoid, anthocyanin, superoxide dismutase, peroxidase, catalase, glutathione reductase activities, antioxidant reducing power, phosphomolybdate activity, DPPH reduction activity, H2O2 scavenging activity, lipid content and organic carbon also supports the fact that the presence of biomass of microalgae and aquatic macrophytes tend to affect the process of microalgae biofilm formation and the ability of the biofilm to produce antioxidant. This high nutrient utilization leads to the production of biomass which can be used for biofuel production and other biotechnological products.


Assuntos
Aphanizomenon/fisiologia , Araceae/fisiologia , Biofilmes , Chlorella vulgaris/fisiologia , Microalgas/fisiologia , Antioxidantes/farmacologia , Biofilmes/efeitos dos fármacos , Estresse Oxidativo/efeitos dos fármacos , Espécies Reativas de Oxigênio
2.
Nutrients ; 13(2)2021 Feb 09.
Artigo em Inglês | MEDLINE | ID: mdl-33572056

RESUMO

Marine and freshwater algae and their products are in growing demand worldwide because of their nutritional and functional properties. Microalgae (unicellular algae) will constitute one of the major foods of the future for nutritional and environmental reasons. They are sources of high-quality protein and bioactive molecules with potential application in the modern epidemics of obesity and diabetes. They may also contribute decisively to sustainability through carbon dioxide fixation and minimization of agricultural land use. This paper reviews current knowledge of the effects of consuming edible microalgae on the metabolic alterations known as metabolic syndrome (MS). These microalgae include Chlorella, Spirulina (Arthrospira) and Tetraselmis as well as Isochrysis and Nannochloropsis as candidates for human consumption. Chlorella biomass has shown antioxidant, antidiabetic, immunomodulatory, antihypertensive, and antihyperlipidemic effects in humans and other mammals. The components of microalgae reviewed suggest that they may be effective against MS at two levels: in the early stages, to work against the development of insulin resistance (IR), and later, when pancreatic -cell function is already compromised. The active components at both stages are antioxidant scavengers and anti-inflammatory lipid mediators such as carotenoids and -3 PUFAs (eicosapentaenoic acid/docosahexaenoic acid; EPA/DHA), prebiotic polysaccharides, phenolics, antihypertensive peptides, several pigments such as phycobilins and phycocyanin, and some vitamins, such as folate. As a source of high-quality protein, including an array of bioactive molecules with potential activity against the modern epidemics of obesity and diabetes, microalgae are proposed as excellent foods for the future. Moreover, their incorporation into the human diet would decisively contribute to a more sustainable world because of their roles in carbon dioxide fixation and reducing the use of land for agricultural purposes.


Assuntos
Fatores Biológicos/administração & dosagem , Doenças Metabólicas/prevenção & controle , Doenças Metabólicas/terapia , Microalgas , Animais , Anti-Inflamatórios/administração & dosagem , Antioxidantes/administração & dosagem , Chlorella/química , Diabetes Mellitus , Dieta , Proteínas na Dieta/administração & dosagem , Alimento Funcional , Humanos , Hipoglicemiantes/administração & dosagem , Microalgas/química , Microalgas/fisiologia , Obesidade , Spirulina/química
3.
Ecotoxicol Environ Saf ; 213: 112024, 2021 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-33582410

RESUMO

Combined pollutions of arsenic (As) and copper (Cu) are common in water bodies near mines, non-ferrous metal smelting and power plants. This study investigated the effect of Cu(II) on the absorption and speciation of As(V) by microalgae. We compared the absorption and speciation of arsenic by microalgae (mainly Cyanophyta and Chlorophyta) when exposed to single As(V) with that exposed to As-Cu co-exposure in laboratory. The results showed that in the case of single As(V) exposure, the inhibitory effect of As(V) on microalgae was primarily affected by the exposure time, instead of the concentration of As(V) in the water solution. Compared with single As(V) exposure, the presence of Cu(II) under As-Cu co-exposure promoted the absorption and accumulation of As(V) by algae. The combination effect of As and Cu on algae was antagonistic instead of synergistic within the tolerance range of algae to them. In the presence of Cu(II), more monomethylarsonous acid (MMA) and dimethylarsinous acid (DMA), which are volatile organic arsenic compounds, were produced in algae compared with the control. The finding that Cu(II) can mediate the absorption and speciation processes of arsenic in algae has significance in possible bioremediation of arsenic pollution in aquatic environment.


Assuntos
Arsênio/toxicidade , Cobre/toxicidade , Microalgas/fisiologia , Arsenicais , Ácido Cacodílico/análogos & derivados , Compostos Organometálicos
4.
Cells ; 10(1)2021 01 08.
Artigo em Inglês | MEDLINE | ID: mdl-33429949

RESUMO

Cyanobacteria and microalgae present in the aquatic or terrestrial environment may be emitted into the air and transported along with air masses over long distances. As a result of staying in the atmosphere, these organisms may develop a greater tolerance to stressful factors, but this topic is still relatively unknown. The main aim was to show an autecological characteristic of some airborne microalgae and cyanobacteria strains by a factorial laboratory experiment approach, including changes in irradiance, temperature, and salinity conditions. The additional purpose of this work was also to present part of the Culture Collection of Baltic Algae (CCBA) collection, which consists of airborne algae (AA) isolated from the atmospheric air of the southern Baltic Sea region. Altogether, 61 strains of airborne cyanobacteria and microalgae from the southern Baltic Sea region were isolated from May 2018 to August 2020. Selected microorganisms were tested in controlled laboratory conditions to identify their response to different irradiance (10-190 µmol photons m-2 s-1), temperature (13-23 °C), and salinity conditions (0-36 PSU). The highest numbers of cells (above 30 × 105 cell mL-1) were recorded for cyanobacterium Nostoc sp., and for diatoms Nitzschia sp., Amphora sp., and Halamphora sp. We found that for cyanobacterium Nostoc sp. as well as for green alga Coccomyxa sp. the maximum cell concentrations were recorded at the salinity of 0 PSU. Moreover, cyanobacteria Planktolyngbya contorta, Pseudanabaena catenata, Leptolyngbya foveolarum, Gloeocapsa sp., and Rivularia sp. were able to grow only at a salinity of 0 PSU. On the other hand, in the range of 16-24 PSU, the highest cell numbers of examined diatoms have been identified. Our research provided that deposited airborne microalgae and cyanobacteria showed full colonization potential. The present experiment suggests that the adaptive abilities of microorganisms, in particular those producing toxins, may contribute to the spread in the future. Thus, it may increase human exposure to their negative health effects. Any distinctive adaptations of the genera give them an additional competitive advantage and a greater chance for territorial expansion.


Assuntos
Cianobactérias/isolamento & purificação , Cianobactérias/fisiologia , Microalgas/isolamento & purificação , Microalgas/fisiologia , Fotossíntese , Cianobactérias/efeitos da radiação , Luz , Microalgas/efeitos da radiação , Oceanos e Mares , Complexo de Proteína do Fotossistema II/metabolismo , Pigmentos Biológicos/metabolismo , Teoria Quântica , Temperatura
5.
Chemosphere ; 262: 127939, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-33182115

RESUMO

Species specific nitrogen-to-phosphorus molar ratio (NPR) has been suggested for green microalgae. Algae can store nitrogen and phosphorus, suggesting that the optimum feed concentration dynamically changes as function of the nutrient storage. We assessed the effect of varying influent NPR on microalgal cultivation in terms of microbial community stability, effluent quality and biokinetics. Mixed green microalgae (Chlorella sorokiniana and Scenedesmus sp.) and a monoculture of Chlorella sp. were cultivated in continuous laboratory-scale reactors treating used water. An innovative image analysis tool, developed in this study, was used to track microbial community changes. Diatoms proliferated as influent NPR decreased, and were outcompeted once cultivation conditions were restored to the optimal NPR range. Low NPR operation resulted in decrease in phosphorus removal, biomass concentration and effluent nitrogen concentration. ASM-A kinetic model simulation results agreed well with operational data in the absence of diatoms. The failure to predict operational data in the presence of diatoms suggest differences in microbial activity that can significantly influence nutrient recovery in photobioreactors (PBR). No contamination occurred during Chlorella sp. monoculture cultivation with varying NPRs. Low NPR operation resulted in decrease in biomass concentration, effluent nitrogen concentration and nitrogen quota. The ASM-A model was calibrated for the monoculture and the simulations could predict the experimental data in continuous operation using a single parameter subset, suggesting stable biokinetics under the different NPR conditions. Results show that controlling the influent NPR is effective to maintain the algal community composition in PBR, thereby ensuring effective nutrients uptake.


Assuntos
Microalgas/fisiologia , Nitrogênio/análise , Fósforo/análise , Purificação da Água/métodos , Biomassa , Chlorella , Nutrientes , Fotobiorreatores , Scenedesmus , Águas Residuárias , Água
6.
Chemosphere ; 263: 127934, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-32828055

RESUMO

A high ammonia concentration and chemical oxygen demand (COD) in piggery wastewater force it to be diluted before conventional microalgal treatment to reduce ammonia toxicity. Incomplete treatment of ammonia and COD in piggery wastewater may cause eutrophication, resulting in algal blooms. This study tried to treat raw piggery wastewater without dilution, using three strains of microalgae (Chlorella sorokiniana, Coelastrella sp. and Acutodesmus nygaardii) that outcompeted other algae under heterotrophic, mixotrophic, and autotrophic conditions, respectively, through adaptive evolution at high ammonia concentration. The three stepwise processes were designed to remove (1) small particles, COD, and phosphorus in the 1st heterotrophic C. sorokiniana cultivation, (2) ammonia and COD in the 2nd mixotrophic Coelastrella sp. cultivation, and (3) the remaining ammonia in the 3rd photoautotrophic A. nygaardii cultivation. To enhance ammonia uptake rate, each algal species were inoculated after 2-day nitrogen starvation. When the N-starved three species were inoculated at each step sequentially at 7 g/L for 2 days, the final phosphorus, COD, and ammonia removal efficiencies were 100% (16.4-0 mg/L), 92% (6820-545 mg/L), 90% (850-81 mg/L) and turbidity (99%) after total 6 days.


Assuntos
Adaptação Fisiológica/fisiologia , Amônia/metabolismo , Biodegradação Ambiental , Microalgas/fisiologia , Eliminação de Resíduos Líquidos/métodos , Animais , Processos Autotróficos , Análise da Demanda Biológica de Oxigênio , Biomassa , Chlorella , Processos Heterotróficos , Nitrogênio , Fósforo , Suínos , Águas Residuárias
7.
Chemosphere ; 263: 127942, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-32835976

RESUMO

Short-chain fatty acids (SCFAs) are considered building blocks for bioproducts in the so-called carboxylate platform. These compounds can be sustainably produced via anaerobic fermentation (AF) of organic substrates, such as microalgae. However, SCFAs bioconversion efficiency is hampered by the hard cell wall of some microalgae. In this study, one thermal and two enzymatic pretreatments (carbohydrases and proteases) were employed to enhance Chlorella vulgaris biomass solubilization prior to AF. Pretreated and non-pretreated microalgae were assessed in continuous stirred tank reactors (CSTRs) for SCFAs production. Aiming to understand microorganisms' roles in AF depending on the employed substrate, not only bioconversion yields into SCFAs were evaluated but microbial communities were thoroughly characterized. Proteins were responsible for the inherent limitation of raw biomass conversion into SCFAs. Indeed, the proteolytic pretreatment resulted in the highest bioconversion (33.4% SCFAs-COD/CODin), displaying a 4-fold enhancement compared with raw biomass. Population dynamics revealed a microbial biodiversity loss along the AF regardless of the applied pretreatment, evidencing that the imposed operational conditions specialized the microbial community. In fact, a reduced abundance in Euryarchaeota phylum explained the low methanogenic activity, implying SCFAs accumulation. The bacterial community developed in the reactors fed with pretreated microalgae exhibited high acidogenic activities, being dominated by Firmicutes and Bacteroidetes. Firmicutes was by far the dominant phylum when using protease (65% relative abundance) while Bacteroidetes was prevailing in the reactor fed with carbohydrase-pretreated microalgae biomass (40% relative abundance). This fact indicated that the applied pretreatment and macromolecule solubilization have a strong effect on microbial distribution and therefore in SCFAs bioconversion yields.


Assuntos
Microalgas/fisiologia , Anaerobiose , Bactérias/metabolismo , Bacteroidetes , Biodiversidade , Biomassa , Metabolismo dos Carboidratos , Chlorella vulgaris , Ácidos Graxos Voláteis/metabolismo , Fermentação/fisiologia , Firmicutes , Microalgas/metabolismo , Microbiota
8.
Proc Biol Sci ; 287(1940): 20201860, 2020 12 09.
Artigo em Inglês | MEDLINE | ID: mdl-33290681

RESUMO

Mutualistic symbioses are common, especially in nutrient-poor environments where an association between hosts and symbionts can allow the symbiotic partners to persist and collectively out-compete non-symbiotic species. Usually these mutualisms are built on an intimate transfer of energy and nutrients (e.g. carbon and nitrogen) between host and symbiont. However, resource availability is not consistent, and the benefit of the symbiotic association can depend on the availability of resources to mutualists. We manipulated the diets of two temperate sea anemone species in the genus Anthopleura in the field and recorded the responses of sea anemones and algal symbionts in the family Symbiodiniaceae to our treatments. Algal symbiont density, symbiont volume and photosynthetic efficiency of symbionts responded to changes in sea anemone diet, but the responses depended on the species of sea anemone. We suggest that temperate sea anemones and their symbionts can respond to changes in anemone diet, modifying the balance between heterotrophy and autotrophy in the symbiosis. Our data support the hypothesis that symbionts are upregulated or downregulated based on food availability, allowing for a flexible nutritional strategy based on external resources.


Assuntos
Meio Ambiente , Microalgas/fisiologia , Anêmonas-do-Mar/fisiologia , Simbiose/fisiologia , Animais , Dieta , Fotossíntese
9.
Nat Commun ; 11(1): 6253, 2020 12 07.
Artigo em Inglês | MEDLINE | ID: mdl-33288750

RESUMO

Domesticator-domesticate relationships are specialized mutualisms where one species provides multigenerational support to another in exchange for a resource or service, and through which both partners gain an advantage over individuals outside the relationship. While this ecological innovation has profoundly reshaped the world's landscapes and biodiversity, the ecological circumstances that facilitate domestication remain uncertain. Here, we show that longfin damselfish (Stegastes diencaeus) aggressively defend algae farms on which they feed, and this protective refuge selects a domesticator-domesticate relationship with planktonic mysid shrimps (Mysidium integrum). Mysids passively excrete nutrients onto farms, which is associated with enriched algal composition, and damselfish that host mysids exhibit better body condition compared to those without. Our results suggest that the refuge damselfish create as a byproduct of algal tending and the mutual habituation that damselfish and mysids exhibit towards one another were instrumental in subsequent mysid domestication. These results are consistent with domestication via the commensal pathway, by which many common examples of animal domestication are hypothesized to have evolved.


Assuntos
Domesticação , Ecossistema , Peixes/fisiologia , Invertebrados/fisiologia , Simbiose/fisiologia , Animais , Belize , Biodiversidade , Recifes de Corais , Peixes/classificação , Geografia , Invertebrados/classificação , Microalgas/classificação , Microalgas/fisiologia
10.
PLoS One ; 15(12): e0244095, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-33382741

RESUMO

Fluorescent natural compounds have been identified in several marine hosts of microalgae. Their prevalence, and the energy the host is expending on their synthesis, suggests an important, yet poorly understood ecological role. It has been suggested that some of these natural products may enhance the photosynthesis of microbial symbionts. In this study, the effect of Ageladine A (Ag A), a pH-dependent fluorophore found in sponges of the genus Agelas, on the photosynthesis of nine microalgal species and strains was examined. The data showed that the variety of effects of Ag A additions differed between species, and even strains within a species. While in one strain of Synechococcus sp., the presence of Ag A increased gross photosynthesis under UV light exposure, it decreased in another. And while in the chlorophyte T. chuii overall metabolic activity was greatly reduced under all forms of lighting, photosynthesis in T. lutea was positively affected by the addition of Ag A. The variety of effects of Ag A on photosynthesis observed in this study indicate a complex interaction of Ag A with microalgal cells and suggests that a host may be able to shape its own symbiotic microbiome with self-produced natural products.


Assuntos
Agelas/microbiologia , Microalgas/fisiologia , Fotossíntese/efeitos dos fármacos , Pirróis/farmacologia , Simbiose/fisiologia , Animais , Microalgas/classificação , Pirróis/metabolismo , Simbiose/efeitos dos fármacos
11.
Sensors (Basel) ; 20(19)2020 Oct 02.
Artigo em Inglês | MEDLINE | ID: mdl-33023245

RESUMO

We report on the observation of the detachment in situ and in vivo of Dunaliella tertiolecta microalgae cells from a glass surface using a 1064 nm wavelength trapping laser beam. The principal bends of both flagella of Dunaliella were seen self-adhered to either the top or bottom coverslip surfaces of a 50 µm thick chamber. When a selected attached Dunaliella was placed in the trapping site, it photoresponded to the laser beam by moving its body and flagellar tips, which eventually resulted in its detachment. The dependence of the time required for detachment on the trapping power was measured. No significant difference was found in the detachment time for cells detached from the top or bottom coverslip, indicating that the induced detachment was not due solely to the optical forces applied to the cells. After detachment, the cells remained within the optical trap. Dunaliella detached from the bottom were seen rotating about their long axis in a counterclockwise direction, while those detached from the top did not rotate. The rotation frequency and the minimal force required to escape from the trap were also measured. The average rotation frequency was found to be independent of the trapping power, and the swimming force of a cell escaping the laser trap ranged from 4 to 10 picoNewtons. Our observations provide insight into the photostimulus produced when a near-infrared trapping beam encounters a Dunaliella. The microalgae frequently absorb more light than they can actually use in photosynthesis, which could cause genetic and molecular changes. Our findings may open new research directions into the study of photomovement in species of Dunaliella and other swimming microorganisms that could eventually help to solve technological problems currently confronting biomass production. In future work, studies of the response to excess light may uncover unrecognized mechanisms of photoprotection and photoacclimation.


Assuntos
Clorofíceas/fisiologia , Microalgas/fisiologia , Pinças Ópticas , Vidro , Lasers , Luz , Fotossíntese
12.
Aquat Toxicol ; 228: 105650, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-33035767

RESUMO

Micro(nano)plastics (MPs/NPs) are already present as contaminants in the natural environment globally and have been shown to be difficult to degrade, resulting in the potential for ecological damage and public health concerns. However, the adverse effects of exposure to MPs/NPs by aquatic organisms, especially freshwater microalgae, remains unclear. In the present study, the growth, physiology and transcriptome of the freshwater microalgae Euglena gracilis were comprehensively analyzed following exposure to 1 mg/L of polystyrene (PS) microbeads (5 µm PS-MPs and 100 nm PS-NPs), 0.5 mg/L cadmium (Cd), or a mixture of PS microbeads and Cd for 96 h. Results showed that the toxicity of PS-MPs to microalgae was greater than PS-NPs, inducing increased growth inhibition, oxidative damage and decreased photosynthesis pigment concentrations. PS-MPs alone or in combination with Cd caused cavitation within microalgal cells, as well as increasing the number and volume of vacuoles. The combined exposure toxicity test showed that a combination of Cd + PS-NPs was more toxic than Cd + PS-MPs, which may be explained by the transcriptomic analysis results. Differentially expressed genes (DEGs) in the Cd + PS-NPs group were mainly enriched in metabolism-related pathways, suggesting that algal metabolism was hindered, resulting in aggravation of toxicity. The reduced toxicity induced by Cd + PS-MPs may indicate a response to resist external stress processes. In addition, no adsorption of 0.5 mg/L Cd to 1 mg/L PS microbeads was observed, suggesting that adsorption of MPs/NPs and Cd was not the key factor determining the combined toxicity effects in this study.


Assuntos
Cádmio/toxicidade , Exposição Ambiental , Euglena gracilis/genética , Euglena gracilis/fisiologia , Microalgas/genética , Microesferas , Poliestirenos/toxicidade , Transcrição Genética/efeitos dos fármacos , Organismos Aquáticos/efeitos dos fármacos , Organismos Aquáticos/genética , Organismos Aquáticos/crescimento & desenvolvimento , Euglena gracilis/efeitos dos fármacos , Euglena gracilis/ultraestrutura , Perfilação da Expressão Gênica , Ontologia Genética , Microalgas/efeitos dos fármacos , Microalgas/fisiologia , Microalgas/ultraestrutura , Estresse Oxidativo/efeitos dos fármacos , Fotossíntese/efeitos dos fármacos , Pigmentos Biológicos/metabolismo , Poluentes Químicos da Água/toxicidade
13.
Sci Rep ; 10(1): 13984, 2020 08 19.
Artigo em Inglês | MEDLINE | ID: mdl-32814827

RESUMO

Viable microalgae occur in the air. Whether they can survive the stresses such as UV, desiccation and freezing temperatures at high altitudes during long distance dispersal is rarely studied. If yes, what mechanisms confer the tolerance? Four freshwater airborne green microalgae were isolated from Dongsha Atoll in the South China Sea, classified as Scenedesmus sp. DSA1, Coelastrella sp. DSA2, Coelastrella sp. DSA3 and Desmodesmus sp. DSA6 based on their morphologies and ITS sequences. Their survival rates under UV stress were tightly correlated with their cell wall thickness. All the four airborne green microalgae survived the air-dry stress on benchtop followed by - 20 °C freeze-desiccation stress for 4 weeks, but not the two waterborne green microalgae Desmodesmus sp. F5 and Neodesmus sp. UTEX 2219-4 used as controls. Three of the four airborne microalgae survived the lyophilization treatment, excluding Desmodesmus sp. DSA6 and the two waterborne microalgae. The four airborne microalgae produced carotenoids under prolonged stress conditions, which might help detoxify the reactive oxygen species generated under environmental stresses and shield from the high-light stress in the air. Characterization of these airborne microalgae may help answer how the descendants of green algae survived on the land about 450 MYA.


Assuntos
Microbiologia do Ar , Clorofíceas/fisiologia , Microalgas/fisiologia , Scenedesmus/fisiologia , Adaptação Fisiológica/fisiologia , Biomassa , Carotenoides/metabolismo , China , Clorofíceas/genética , Clorofíceas/ultraestrutura , DNA Espaçador Ribossômico/genética , Microalgas/classificação , Microalgas/genética , Microscopia Eletrônica de Varredura , Microscopia Eletrônica de Transmissão , Filogenia , RNA Ribossômico/genética , Scenedesmus/genética , Scenedesmus/ultraestrutura , Estresse Fisiológico/fisiologia
14.
Archaea ; 2020: 8815263, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32760214

RESUMO

At present, large-scale and high-efficiency microalgal cultivation is the key to realizing the technology for carbon capture and storage (CCS) and bioresource recovery. Meanwhile, tubular photobioreactors (PBRs) have great potential for microalgal cultivation due to their high productivity. To improve the mixing performance and flashing-light effect, a novel tube PBR with the inner tube tangential to the outer tube was developed, whose radial aeration pores are situated along the length of the inner tube. The direction of aeration, aeration rate, light/dark cycle period (L/D), light-time ratio, average turbulent kinetic energy (TKE), and degree of synergy between the velocity and direction of the light field in the PBR were optimized by a computational fluid dynamics (CFD) simulation and field synergy theory. The results show that a downwards aeration direction of 30° and an aeration rate of 0.7 vvm are the most conducive to reducing the dead zone and improving the light/dark cycle frequency. Compared to the concentric double-tube PBR, the light/dark cycle frequency and light time of the tangent double-tube PBR increased by 78.2% and 36.2% to 1.8 Hz and 47.8%, respectively, and the TKE was enhanced by 48.1% from 54 to 80 cm2·s-2. Meanwhile, field synergy theory can be extended and applied to the design of tubular microalgae PBRs, and the average synergy of the light and velocity gradients across the cross-section increased by 38% to 0.69. The tangential inner tube aeration structure generated symmetrical vertical vortices between the light and dark areas in the PBR, which significantly improved the mixing performance and flashing-light effect. This novel design can provide a more suitable microenvironment for microalgal cultivation and is promising for bioresource recovery applications and improving the yield of microalgae.


Assuntos
Hidrodinâmica , Luz , Microalgas/fisiologia , Fotobiorreatores , Fotoperíodo , Biomassa , Simulação por Computador , Oxigênio
15.
Ecotoxicol Environ Saf ; 203: 111000, 2020 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-32736119

RESUMO

Microplastics are identified as a great threat to marine environments. However, knowledge of their impacts on phytoplankton, especially for the diatoms is scarce. Herein, the effects of different polyvinyl chloride (PVC) microplastic concentrations and contact times (24, 48, 72 and 96 h) on the Fv/Fm and cell density of Phaeodactylum tricornutum (B255), Chaetoceros gracilis (B13) and Thalassiosira sp. (B280) were investigated to evaluate the toxic effects of microplastics on marine diatoms. The effects of PVC microplastics on the morphology of the diatoms was observed by SEM. The order of sensitivity to 1 µm PVC microplastics among three marine diatoms was B13 > B280 > B255, showing that the toxic effects varied with different microalgae species. Furthermore, the presence of a siliceous cell wall played a minimal role in protecting cells from the physical attack of PVC microplastics, with no significant difference from the common cell wall. PVC microplastics caused dose-dependent adverse effects on three marine diatoms. High PVC concentrations (200 mg/L) reduced the chlorophyll content, inhibited Fv/Fm, and affected the photosynthesis of three marine diatoms. The PVC microplastics adsorbed and caused physical damage on the structure of algal cells. Interactions between PVC microplastics and diatoms may be the probable reason for the negative effects of PVC on diatoms.


Assuntos
Diatomáceas/efeitos dos fármacos , Microplásticos/toxicidade , Cloreto de Polivinila/toxicidade , Poluentes Químicos da Água/toxicidade , Adsorção , Clorofila/metabolismo , Diatomáceas/crescimento & desenvolvimento , Diatomáceas/fisiologia , Relação Dose-Resposta a Droga , Microalgas/efeitos dos fármacos , Microalgas/crescimento & desenvolvimento , Microalgas/fisiologia , Fotossíntese/efeitos dos fármacos , Fitoplâncton/efeitos dos fármacos , Fitoplâncton/crescimento & desenvolvimento , Fitoplâncton/fisiologia , Fatores de Tempo
16.
Sci Rep ; 10(1): 14060, 2020 08 20.
Artigo em Inglês | MEDLINE | ID: mdl-32820199

RESUMO

This study analyses the interactions among crustose and lichenicolous lichens growing on gypsum biocrusts. The selected community was composed of Acarospora nodulosa, Acarospora placodiiformis, Diploschistes diacapsis, Rhizocarpon malenconianum and Diplotomma rivas-martinezii. These species represent an optimal system for investigating the strategies used to share phycobionts because Acarospora spp. are parasites of D. diacapsis during their first growth stages, while in mature stages, they can develop independently. R. malenconianum is an obligate lichenicolous lichen on D. diacapsis, and D. rivas-martinezii occurs physically close to D. diacapsis. Microalgal diversity was studied by Sanger sequencing and 454-pyrosequencing of the nrITS region, and the microalgae were characterized ultrastructurally. Mycobionts were studied by performing phylogenetic analyses. Mineralogical and macro- and micro-element patterns were analysed to evaluate their influence on the microalgal pool available in the substrate. The intrathalline coexistence of various microalgal lineages was confirmed in all mycobionts. D. diacapsis was confirmed as an algal donor, and the associated lichenicolous lichens acquired their phycobionts in two ways: maintenance of the hosts' microalgae and algal switching. Fe and Sr were the most abundant microelements in the substrates but no significant relationship was found with the microalgal diversity. The range of associated phycobionts are influenced by thallus morphology.


Assuntos
Biodiversidade , Sulfato de Cálcio , Líquens/fisiologia , Microalgas/classificação , Solo , Simbiose , Ecossistema , Interações Hospedeiro-Parasita , Microalgas/fisiologia , Filogenia
17.
PLoS One ; 15(8): e0237211, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32760132

RESUMO

Understanding the dynamics of microphytobenthos biomass and photosynthetic performances in intertidal ecosystems will help advance our understanding of how trophic networks function in order to optimize ecological management and restoration projects. The main objective of this study was to investigate microphytobenthic biomass and photosynthetic performances as a function of the sedimentary and environmental variabilities in the range of intertidal habitats in the downstream Seine estuary (Normandy, France). Our results highlight higher biomass associated with more stratified biofilms and better photosynthetic performances in areas characterized by a sand/mud mixture (40-60% of mud) compared to pure sand or pure mud environments. This type of sediment probably offers an efficient trade-off between the favorable characteristics of the two types of sediments (sand and mud) with respect to light penetration and nutrient accessibility. Moreover, the large quantities of exopolysaccharides produced in sand/mud mixtures emphasizes the functional role played by microphytobenthos in promoting sediment stability against erosion. This allows us to show that despite the strong increase in sand content of the downstream Seine estuary, intertidal flats are still productive since microphytobenthic biomass, photosynthetic performances and exopolysaccharides secretion are highest in sand-mud mixtures. This study also underlines the impact of ecosystem modifications due to human disturbance and climate change on the dynamics of key primary producers in estuaries.


Assuntos
Biomassa , Cianobactérias/fisiologia , Estuários , Microalgas/fisiologia , Biofilmes , Sedimentos Geológicos/microbiologia , Fotossíntese
18.
PLoS One ; 15(7): e0236188, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32701995

RESUMO

Microalgae and cyanobacteria are considered as important model organisms to investigate the biology of photosynthesis; moreover, they are valuable sources of biomolecules for several biotechnological applications. Understanding the species-specific traits of photosynthetic electron transport is extremely important, because it contributes to the regulation of ATP/NADPH ratio, which has direct/indirect links to carbon fixation and other metabolic pathways and thus overall growth and biomass production. In the present work, a cuvette-based setup is developed, in which a combination of measurements of dissolved oxygen, pH, chlorophyll fluorescence and NADPH kinetics can be performed without disturbing the physiological status of the sample. The suitability of the system is demonstrated using a model cyanobacterium Synechocystis sp. PCC6803, as well as biofuel-candidate microalgae species, such as Chlorella sorokiniana, Dunaliella salina and Nannochloropsis limnetica undergoing inorganic carbon (Ci) limitation. Inorganic carbon limitation, induced by photosynthetic Ci uptake under continuous illumination, caused a decrease in the effective quantum yield of PSII (Y(II)) and loss of oxygen-evolving capacity in all species investigated here; these effects were largely recovered by the addition of NaHCO3. Detailed analysis of the dark-light and light-dark transitions of NADPH production/uptake and changes in chlorophyll fluorescence kinetics revealed species- and condition-specific responses. These responses indicate that the impact of decreased Calvin-Benson cycle activity on photosynthetic electron transport pathways involving several sections of the electron transport chain (such as electron transfer via the QA-QB-plastoquinone pool, the redox state of the plastoquinone pool) can be analyzed with high sensitivity in a comparative manner. Therefore, the integrated system presented here can be applied for screening for specific traits in several significant species at different stages of inorganic carbon limitation, a condition that strongly impacts primary productivity.


Assuntos
Carbono/farmacologia , Cianobactérias/fisiologia , Compostos Inorgânicos/farmacologia , Microalgas/fisiologia , Fotossíntese , Chlorella/efeitos dos fármacos , Chlorella/fisiologia , Clorofila/metabolismo , Cianobactérias/efeitos dos fármacos , Transporte de Elétrons/efeitos dos fármacos , Fluorescência , Cinética , Microalgas/efeitos dos fármacos , NADP/metabolismo , Oxigênio/metabolismo , Fotossíntese/efeitos dos fármacos , Complexo de Proteína do Fotossistema II/metabolismo , Teoria Quântica , Synechocystis/efeitos dos fármacos , Synechocystis/fisiologia
19.
Gene ; 757: 144929, 2020 Oct 05.
Artigo em Inglês | MEDLINE | ID: mdl-32622990

RESUMO

Phaeodactylum tricornutum is a model microalgae that is widely used to study diatom physiology and ecology. Since the meiotic process and sexual cycle have never been observed directly, P. tricornutum has been considered to be an asexual species. However, phylogenetic analysis of the P. tricornutum genome has revealed a series of meiosis-specific gene homologues in this species. We identified two copies of differently transcribed SPO11 homologs that contain the conserved motifs of Winged-helix and Toprim domains. The homolog PtSPO11-3 interacts with TopoVIB in yeast two-hybrid analysis, whereas the homolog PtSPO11-2 could rescue the sporulation defect of a Spo11 yeast mutant strain. PtSPO11-2 was also found to be significantly up-regulated at low temperatures in P. tricornutum and its key catalytic residue was important to the homolog's function in sporulation. The results herein provide positive clue that meiosis and sexual reproduction could exist in this diatom.


Assuntos
Domínio Catalítico , Diatomáceas/genética , Endodesoxirribonucleases/metabolismo , Meiose , Microalgas/genética , Sequência Conservada , Diatomáceas/fisiologia , Endodesoxirribonucleases/química , Endodesoxirribonucleases/genética , Microalgas/fisiologia , Ligação Proteica , Multimerização Proteica
20.
Chemosphere ; 259: 127418, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32574848

RESUMO

This work evaluated the effect of different initial biomass ratios in a co-culture of an alkaliphilic methanotrophic bacteria consortium (AMB) and the green microalga Scenedesmus obtusiusculus (GM) on the maximum CH4 specific biodegradation rate and global carbon uptake. The highest maximum specific biodegradation rate was 589 ± 0.01 mgCH4 gbiomass-1 d-1 obtained for a proportion of 3:1 AMB-GM (w w-1) and 8% of initial CH4 in the headspace. The methane degradation rate was 1.5 times lower than the value obtained solely by the AMB consortium, and it was associated with pH increases due to the evolved CO2 consumption by the microalga. Increased activity of the AMB consortium along the experiments was due to progressive adaptation. Massive sequencing revealed the presence of methanotrophic/methylotrophic species such as Methylocystis sp., Methylomicrobium sp., Methylophaga sp., and Hyphomicrobium sp. Successful complete methane and carbon dioxide uptake was obtained with the 3:1, 4:1, and 5:1 AMB-GM biomass ratios, while for the rest of the ratios tested, more than 70% of the initial methane was transformed into biomass and inorganic carbon. This study showed that methanotrophic-microalgal co-cultures lead to a promising strategy for greenhouse gases mitigation in one step.


Assuntos
Biodegradação Ambiental , Gases de Efeito Estufa , Metano/metabolismo , Microalgas/fisiologia , Biomassa , Dióxido de Carbono/metabolismo , Técnicas de Cocultura , Methylocystaceae , Microalgas/metabolismo , Scenedesmus/metabolismo
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