RESUMO
Our knowledge of the effects of copper on microalgal physiology is largely based on studies conducted with high copper concentrations; much less is known when environmentally relevant copper levels come into question. Here, we evaluated the physiology of Chlorolobion braunii exposed to free copper ion concentrations between 5.7 × 10-9 and 5.0 × 10-6 mol · L-1 , thus including environmentally relevant values. Population growth and maximum photosynthetic quantum yield of PSII were determined daily during the 96 h laboratory controlled experiment. Exponentially-growing cells (48 h) were analyzed for effective quantum yield and rapid light curves (RLC), and total lipids, proteins, carbohydrates, chlorophyll a and carotenoids were determined. The results showed that growth rates and population density decreased gradually as copper increased in experiment, but the photosynthetic parameters (maximum and effective quantum yields) and photochemical quenching (qP) decreased only at the highest free copper concentration tested (5.0 × 10-6 mol · L-1 ); nonphotochemical quenching (NPQ) increased gradually with copper increase. The RLC parameters Ek and rETRmax were inversely proportional to copper concentration, while α and Im decreased only at 5.0 × 10-6 mol · L-1 . The effects of copper in biomolecules yield (mg · L-1 ) varied depending on the biomolecule. Lipid yield increased at free copper concentration as low as 2.5 × 10-8 mol · L-1 , but proteins and carbohydrates were constant throughout.
Assuntos
Microalgas , Fotossíntese , Clorofila , Clorofila A , CobreRESUMO
Copper is an essential metal for several physiological and metabolic processes, but a narrow range regulate its effect in phytoplankton cells. It can affect the production of biomolecules and be toxic at concentrations slightly above those required, e.g. decreasing photosynthesis and increasing respiration. The aims of this study were to analyse the changes in growth and chlorophyll a synthesis, and in biochemistry (total carbohydrates, proteins, lipids and fatty acids) of the freshwater microalga Selenastrum gracile after exposure to copper. Exponentially growing cells were exposed to 5 concentrations of free copper ions (Cu2+) ranging from 0.7 (control) to 13 × 10-8 M for up to 120 h. Free Cu2+ ion concentrations were calculated through the chemical equilibrium model MINEQL+. We observed that copper was responsible for a decrease in cell density and an increase in total protein and lipid production, but no effect on total carbohydrates was detected. The increase in phospholipids and sterols and a decrease in saturated fatty acids under copper exposure suggest a change in conformation of the cell membrane, by decreasing its fluidity. We suggest this serves the cell as a system to avoid the internalization of metal, thereby acting as a detoxifying mechanism.
Assuntos
Clorófitas/fisiologia , Cobre/toxicidade , Fitoplâncton/fisiologia , Testes de Toxicidade , Poluentes Químicos da Água/toxicidade , Ácidos Graxos , Fosfolipídeos , Fotossíntese/efeitos dos fármacosRESUMO
Nitrogen and phosphorus present in sewage can be used for microalgae growth, possibiliting cost reduction in the production of microalgae at the same time that it decreases the eutrophication potential of the effluent. This research aimed at monitoring the native community of microalgae and coliform bacteria in a secondary effluent from anaerobic municipal sewage treatment. Two treatments (aerated and non-aerated) were performed to grow microalgae under semi-controlled conditions in semi-closed photobioreactors in a greenhouse. The results showed no significant pH and coliforms (total and Escherichia coli ) variation between treatments. Nutrient concentrations were reduced supporting microalgae growth up to 10 (7) cells.mL (-1) independent of aeration. Exponential growth was obtained from the first day for the non-aerated, but a 5 day lag phase of growth was obtained for the aerated. Chlorella vulgaris was the dominant microalgae (99.9%) in both treatments. In the aerated, 5 algae classes were detected (Chlorophyceae, Cyanophyceae, Chrysophyceae, Bacillariophyceae and Euglenophyceae), with 12 taxa, whereas in the non-aerated, 2 classes were identified (Chlorophyceae and Cyanophyceae), with 5 taxa. We concluded that effluent is viable for microalgae growth, especially Chlorella vulgaris, at the same time that the eutrophication potential and coliforms are decreased, contributing for better quality of the final effluent.
Assuntos
Meios de Cultura/química , Microalgas/crescimento & desenvolvimento , Fotobiorreatores/microbiologia , Esgotos/química , Aerobiose , Anaerobiose , Enterobacteriaceae/crescimento & desenvolvimento , Microalgas/classificação , Dinâmica PopulacionalRESUMO
Nitrogen and phosphorus present in sewage can be used for microalgae growth, possibiliting cost reduction in the production of microalgae at the same time that it decreases the eutrophication potential of the effluent. This research aimed at monitoring the native community of microalgae and coliform bacteria in a secondary effluent from anaerobic municipal sewage treatment. Two treatments (aerated and non-aerated) were performed to grow microalgae under semi-controlled conditions in semi-closed photobioreactors in a greenhouse. The results showed no significant pH and coliforms (total and Escherichia coli) variation between treatments. Nutrient concentrations were reduced supporting microalgae growth up to 107 cells.mL−1 independent of aeration. Exponential growth was obtained from the first day for the non-aerated, but a 5 day lag phase of growth was obtained for the aerated. Chlorella vulgaris was the dominant microalgae (99.9%) in both treatments. In the aerated, 5 algae classes were detected (Chlorophyceae, Cyanophyceae, Chrysophyceae, Bacillariophyceae and Euglenophyceae), with 12 taxa, whereas in the non-aerated, 2 classes were identified (Chlorophyceae and Cyanophyceae), with 5 taxa. We concluded that effluent is viable for microalgae growth, especially Chlorella vulgaris, at the same time that the eutrophication potential and coliforms are decreased, contributing for better quality of the final effluent.
Assuntos
Meios de Cultura/química , Microalgas/crescimento & desenvolvimento , Fotobiorreatores/microbiologia , Esgotos/química , Aerobiose , Anaerobiose , Enterobacteriaceae/crescimento & desenvolvimento , Microalgas/classificação , Dinâmica PopulacionalRESUMO
Nitrogen and phosphorus present in sewage can be used for microalgae growth, possibiliting cost reduction in the production of microalgae at the same time that it decreases the eutrophication potential of the effluent. This research aimed at monitoring the native community of microalgae and coliform bacteria in a secondary effluent from anaerobic municipal sewage treatment. Two treatments (aerated and non-aerated) were performed to grow microalgae under semi-controlled conditions in semi-closed photobioreactors in a greenhouse. The results showed no significant pH and coliforms (total and Escherichia coli) variation between treatments. Nutrient concentrations were reduced supporting microalgae growth up to 107 cells.mL−1 independent of aeration. Exponential growth was obtained from the first day for the non-aerated, but a 5 day lag phase of growth was obtained for the aerated. Chlorella vulgaris was the dominant microalgae (99.9%) in both treatments. In the aerated, 5 algae classes were detected (Chlorophyceae, Cyanophyceae, Chrysophyceae, Bacillariophyceae and Euglenophyceae), with 12 taxa, whereas in the non-aerated, 2 classes were identified (Chlorophyceae and Cyanophyceae), with 5 taxa. We concluded that effluent is viable for microalgae growth, especially Chlorella vulgaris, at the same time that the eutrophication potential and coliforms are decreased, contributing for better quality of the final effluent.(AU)
Assuntos
Meios de Cultura/química , Microalgas/crescimento & desenvolvimento , Fotobiorreatores/microbiologia , Esgotos/química , Aerobiose , Anaerobiose , Enterobacteriaceae/crescimento & desenvolvimento , Microalgas/classificação , Dinâmica PopulacionalRESUMO
Cadmium (Cd) is an important industrial and toxic metal. Its fate and toxicity in the environment may be mediated by association with dissolved organic materials excreted by phytoplankton. The aim of the present study was to investigate the trophodynamics and toxicity of Cd complexed with Cylindrospermopsis raciborskii exudates in a plankton food chain. The microbial loop involves heterotrophic bacteria as the primary consumer, which is supplemented with a Cd-exudate complex. The secondary consumer (protozoan Paramecium caudatum) was fed on the bacteria, and the tertiary consumer (copepod Mesocyclops longisetus) on the protozoa. The Cd complexing properties of the exudate were determined before the experiments, to ensure that all Cd was furnished to the organisms as the organic complex alone. The results showed that free Cd2+ ions caused the highest observed toxicity to bacteria, while Cd complexed to the cyanobacterial exudate was less toxic, but could be bioavailable and transferred through the food web. This study is a contribution to aquatic ecosystem management and to current knowledge of Cd dynamics, bioavailability and interaction with aquatic planktonic organisms.
Assuntos
Bactérias/crescimento & desenvolvimento , Cádmio/toxicidade , Cadeia Alimentar , Poluentes Químicos da Água/toxicidade , Animais , Cádmio/metabolismo , Copépodes , Cylindrospermopsis/fisiologia , Ecossistema , Água Doce/microbiologia , Processos Heterotróficos , Plâncton/fisiologia , Microbiologia da Água , Poluentes Químicos da Água/metabolismoRESUMO
The need for clean and low-cost algae production demands for investigations on algal physiological response under different growth conditions. In this research, we investigated the growth, biomass production and biochemical composition of Chlorella vulgaris using semi-continuous cultures employing three growth media (LC Oligo, Chu 10 and WC media). The highest cell density was obtained in LC Oligo, while the lowest in Chu medium. Chlorophyll a, carbohydrate and protein concentrations and yield were highest in Chu and LC Oligo media. Lipid class analysis showed that hydrocarbons (HC), sterol esthers (SE), free fatty acids (FFA), aliphatic alcohols (ALC), acetone mobile polar lipids (AMPL) and phospholipids (PL) concentrations and yields were highest in the Chu medium. Triglyceride (TAG) and sterol (ST) concentrations were highest in the LC Oligo medium. The results suggested that for cost effective cultivation, LC Oligo medium is the best choice among those studied, as it saved the cost of buying vitamins and EDTA associated with the other growth media, while at the same time resulted in the best growth performance and biomass production.
Assuntos
Biomassa , Chlorella vulgaris , Meios de Cultura/farmacologia , Proteínas de Algas/análise , Carboidratos/análise , Chlorella vulgaris/química , Chlorella vulgaris/efeitos dos fármacos , Chlorella vulgaris/crescimento & desenvolvimento , Clorofila/análise , Clorofila A , Lipídeos/análiseRESUMO
The chemical fractionation and bioleaching of Mn, Al, Zn, Cu and Ti in municipal sewage sludge were investigated using Thiobacillus ferrooxidans as leaching microorganism. As a result of the bacterial activity, ORP increase and pH reduction were observed. Metal solubilization was accomplished only in experimental systems supplemented with energy source (Fe(II)). The solubilization efficiency approached approximately 80% for Mn and Zn, 24% for Cu, 10% for Al and 0.2% for Ti. The chemical fractionation of Mn, Al, Zn, Cu and Ti was investigated using a five-step sequential extraction procedure employing KNO3, KF, Na4P2O7, EDTA and HNO3. The results show that the bioleaching process affected the partitioning of Mn and Zn, increasing its percentage of elution in the KNO3 fraction while reducing it in the KF, Na4P2O7 and EDTA fractions. No significant effect was detected on the partitioning of Cu and Al. However, quantitatively the metals Mn, Zn, Cu and Al were extracted with higher efficiency after the bacterial activity. Titanium was unaffected by the bioleaching process in both qualitative and quantitative aspects.