Effects of nutritional conditions on lipid production by cyanobacteria.

The present study evaluated the effects of the culturing media and the levels of nitrogen and phosphorus on the growth, biomass productivity and lipid production of four species of Microcystis (M. novacekii, M. aeruginosa, M panniformis and M. protocystis). The lipid extract was obtained by refluxing with dichloromethane (Soxhlet). The biomass and biomass productivity yields were maximized with ASM-1 medium treatment enriched with nitrogen and/or phosphorus (0.25-0.65 g/L and 25-50.7 mg/L d-1, respectively). The lipid extract yields from M. panniformis and M. novacekii were inversely correlated with the concentration of nitrogen and directly correlated with the concentration of phosphorus (35.8 % and 31.7 %). The lipid extract yield from M. aeruginosa was inversely correlated with the nutrient concentration (23.3 %). M. protocystis exhibited a higher lipid content in the control medium (41.5 %) than in the nitrogen-enriched media. The recorded results show that a nutrient-poor culture medium favours cell growth and stimulates lipid accumulation, which directly affects the cost of cultivation by reducing nutrient consumption. All studied species may serve as biomass sources for biodiesel production, although M. protocystis exhibited the highest lipid production. Further studies are necessary to determine the composition of the recorded lipid extract.

Effects of nutritional conditions on lipid production by cyanobacteria

ABSTRACT The present study evaluated the effects of the culturing media and the levels of nitrogen and phosphorus on the growth, biomass productivity and lipid production of four species of Microcystis (M. novacekii, M. aeruginosa, M panniformis and M. protocystis). The lipid extract was obtained by refluxing with dichloromethane (Soxhlet). The biomass and biomass productivity yields were maximized with ASM-1 medium treatment enriched with nitrogen and/or phosphorus (0.25-0.65 g/L and 25-50.7 mg/L d-1, respectively). The lipid extract yields from M. panniformis and M. novacekii were inversely correlated with the concentration of nitrogen and directly correlated with the concentration of phosphorus (35.8 % and 31.7 %). The lipid extract yield from M. aeruginosa was inversely correlated with the nutrient concentration (23.3 %). M. protocystis exhibited a higher lipid content in the control medium (41.5 %) than in the nitrogen-enriched media. The recorded results show that a nutrient-poor culture medium favours cell growth and stimulates lipid accumulation, which directly affects the cost of cultivation by reducing nutrient consumption. All studied species may serve as biomass sources for biodiesel production, although M. protocystis exhibited the highest lipid production. Further studies are necessary to determine the composition of the recorded lipid extract.

Arsenic biotransformation by cyanobacteria from mining areas: evidences from culture experiments.

Elucidating the role of cyanobacteria in the biotransformation of arsenic (As) oxyanions is crucial to understand the biogeochemical cycle of this element and indicate species with potential for its bioremediation. In this study, we determined the EC50 for As(III) and As(V) and evaluated the biotransformation of As by Synechococcus sp. through high-performance liquid chromatography hyphenated to inductively coupled plasma mass spectrometry (HPLC-ICP-MS) and X-ray absorption fine structure spectroscopy (XAFS). Synechococcus sp. exhibited higher sensitivity to As(III) with an EC(50, 96 h) of 6.64 mg L(-1) that was approximately 400-fold lower than that for As(V). Even though the cells were exposed to concentrations of As(III) (6 mg L(-1)) approximately 67-fold lower than those of As(V) (400 mg L(-1)), similar intracellular concentrations of As (60.0 µg g(-1)) were observed after 30 days. As(V) was the predominant intracellular As species followed by As(III). Furthermore, organic As species such as monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA) were observed in higher proportions after exposure to As(III). The differential toxicity among As oxyanions indicates that determining the redox state of As in the environment is fundamental to estimate toxicity risks to aquatic organisms. Synechococcus sp. demonstrated potential for its application in bioremediation due to the high accumulation of As and production of As organic compounds notably after exposure to As(III).

Evaluation of the capacity of the cyanobacterium Microcystis novacekii to remove atrazine from a culture medium.

The bioaccumulation of atrazine and its toxicity were evaluated for the cyanobacterium Microcystis novacekii. Cyanobacterial cultures were grown in WC culture medium with atrazine at 50, 250 and 500 µg L(-1). After 96 hours of exposure, 27.2% of the atrazine had been removed from the culture supernatant. Spontaneous degradation was found to be insignificant (< 9% at 500 µg L(-1)), indicating a high efficiency for the bioaccumulation of atrazine by M. novacekii. There were no atrazine metabolites detected in the culture medium at any of the doses studied. The acute toxicity (EC(50)) of atrazine to the cyanobacterium was 4.2 mg L(-1) at 96 hours demonstrating the potential for M. novacekii to tolerate high concentrations of this herbicide in fresh water environments. The ability of M. novacekii to remove atrazine combined with its tolerance of the pesticide toxicity showed in this study makes it a potential biological resource for the restoration of contaminated surface waters. These findings support continued studies of the role of M. novacekii in the bioremediation of fresh water environments polluted by atrazine.

Evaluation of the potential of microalgae Microcystis novacekii in the removal of Pb2+ from an aqueous medium.

In this study, the absorption capacity of active and inactive biomass of the microalgae Microcystis novacekii to remove Pb(2+) from aqueous solutions was investigated. This is the first reported study of biosorption by a cyanobacterium species, which is abundant and easily found in eutrophic lakes and ponds in tropical areas of the world. We also evaluated the effects of different concentrations of Pb(2+) on growth rates of M. novacekii. Inactive biomass was characterized by elemental composition, surface area, potentiometric titration, infrared spectroscopy and thermogravimetric analysis (TGA). The biosorption data of Pb(2+) by inactive biomass were analyzed using the Langmuir and Freundlich isotherms. Pb(2+) concentrations higher than 0.5 mg L(-1) inhibited species growth. Potentiometric titrations showed a significantly higher negative surface charge (1.48+/-0.22 mmol g(-1)) with two acidic groups (pKa(1)=3.74+/-0.12 and, pKa(2)=7.25+/-0.30). Analysis of inactive M. novacekii cells by infrared spectroscopy suggests that the cell wall carboxyl and amide groups participate in Pb(2+) biosorption. The maximum Pb(2+) adsorbed was found to be 70 mg g(-1), and the biosorption of Pb(2+) on inactive M. novacekii correlated well (R(2)=0.931) with the Langmuir equation compared to the Freundlich isotherm equation (R(2)=0.823) in the concentration range studied.

Analysis of medical prescriptions dispensed at health centers in Belo Horizonte, Minas Gerais, Brazil.

This article focuses on medical prescriptions dispensed at health centers under the Municipal Health Department in Belo Horizonte, Minas Gerais State, Brazil. The study analyzed 4,607 prescriptions from March to April 1999, grouped according to origin (internal or external). The analysis focused on information written on medical prescriptions. The main findings were: (a) an average of 2.4 drugs per prescription in both groups; (b) prescriptions filled out with 4 or more drugs accounted for 18.0% of internal and 17.6% of external prescriptions; (c) 84.3% of internal and 85.5% of external prescriptions provided no instructions for use of medication; (d) information on dosage regimen varied from 51.2% to 97.6% for internal and 57.9% to 96.5% for external prescriptions; (e) generic names were specified for 51.9% and 28.4% of all drugs on internal and external prescriptions, respectively; (f) prescriptions containing standard drugs from the Municipal Health Department accounted for 88.7% of internal and 76.4% of external prescriptions. Data analysis shows the need for continuing education of physicians and adoption of other methods to improve quality of prescriptions and promote rational use of drugs.

Analysis of medical prescriptions dispensed at health centers in Belo Horizonte, Minas Gerais, Brazil

Este trabalho avalia prescrições médicas aviadas em farmácias de unidades de saúde da Secretaria Municipal de Saúde de Belo Horizonte (SMS-BH), Brasil. Foram analisadas 4.607 prescrições, no período de março a abril de 1999, agrupadas segundo sua origem. A análise enfocou informações que deveriam constar em uma prescrição médica. Os principais resultados encontrados foram: (a) número médio de 2,4 medicamentos/prescrição para os dois grupos; (b) prescrição de quatro ou mais medicamentos em 18,0 por cento das prescrições internas e 17,6 por cento das externas; (c) ausência de recomendações de uso em 84,3 por cento das prescrições internas e 85,5 por cento nas externas; (d) presença de dados posológicos variando de 51,2 por cento a 97,6 por cento nas prescrições internas e de 57,9 por cento a 96,5 por cento nas externas; (e) utilização do nome genérico para todos os medicamentos em 51,9 por cento nas prescrições internas e 28,4 por cento nas externas e (f) prescrição com todos os medicamentos padronizados pela SMS-BH em 88,7 por cento das internas e 76,4 por cento das externas. A análise dos dados demonstra necessidade de educação continuada dos prescritores e adoção de outras medidas para melhoria da qualidade de prescrições, na perspectiva de promover o uso racional de medicamentos.