RESUMO
The phytosterol-biotransforming strains can be selected from Mycobacterium sp. using a high concentration of ß-sitosterol. The selection is made by culturing the strains in a medium enriched with 14 g/L of ß-sitosterol as the unique source of carbon. During 2 months, the bacterial cultures are transferred successively. The extraction of the biotransformation products is made with methanol and ethyl acetate. The qualitative and quantitative analyses are made by means of thin-layer chromatography, gas-liquid chromatography (GLC), and GLC-mass spectrometry. Under these conditions, it is observed that after seven transfers, the strains Mycobacterium sp. MB-3683 and Mycobacterium fortuitum B-11045 increase their biotransformation capacity from 20% to 64% and from 34% to 55%, respectively. The products in the highest proportion identified for each trial are androstenedione and androstadienedione. The results suggest that the high substrate concentration could be a selective mechanism to obtain strains more efficient in the biotransformation of ß-sitosterol into steroidal bases.
Assuntos
Fitosteróis , Cromatografia Gasosa-Espectrometria de Massas , Androstenodiona , Carbono , Cromatografia em Camada FinaRESUMO
The phytosterol-biotransforming strains were selected from Mycobacterium sp., using a high concentration of ß-sitosterol. The selection was made by culturing the strains in a medium enriched with 14 g ß-sitosterol/L as the unique source of carbon. During 2 months, the bacterial cultures were transferred successively. The extraction of the biotransformation products was made with methanol and ethyl acetate. The qualitative and quantitative analysis was made by means of thin-layer chromatography, gas-liquid chromatography (GLC), and GLC-mass spectrometry. Under these conditions, it was observed that after seven transfers, the strains Mycobacterium sp. MB-3683 and the Mycobacterium fortuitum B-11045 increased their biotransformation capacity from 20% to 64% and from 34% to 55%, respectively. The products in the highest proportion identified for each trial were androstenedione and androstadienedione. The results suggest that the high substrate concentration could be a selective mechanism to obtain strains more efficient in the biotransformation of ß-sitosterol into steroidal bases.
Assuntos
Biotransformação/genética , Cromatografia Gasosa-Espectrometria de Massas/métodos , Fitosteróis/metabolismo , Sitosteroides/metabolismo , Mycobacterium/genética , Mycobacterium/metabolismo , Fitosteróis/química , Sitosteroides/químicaRESUMO
Biodegradation of tributyltin (TBT) by four tin resistant Gram negative bacteria isolated from extremely contaminated river sediments in the Atacama Desert in Chile was studied. Moraxella osloensis showed the greatest resistance and degradation capability of TBT, producing less toxic by-products, such as dibutyltin (DBT) and inorganic tin. In 7 days, approximately 80 % of TBT degradation was achieved, generating close to 20 % of DBT as degradation product. The degradation rate constant (k) was 0.022 [day(-1)] and TBT half-life (t1/2) in culture was 4.3 days. Debutylation is stated a probable mechanism of TBT degradation.
Assuntos
Bactérias/metabolismo , Clima Desértico , Compostos Orgânicos de Estanho/análise , Estanho/análise , Compostos de Trialquitina/análise , Alcaligenes/metabolismo , Biodegradação Ambiental , Burkholderia cepacia/metabolismo , Chile , Farmacorresistência Bacteriana , Sedimentos Geológicos/química , Meia-Vida , Moraxella/metabolismo , Pseudomonas/metabolismo , Rios , Solo , Microbiologia do Solo , Poluentes do Solo/análise , Fatores de Tempo , Poluentes da Água/análise , Yersinia/metabolismoRESUMO
Pseudomonas arsenicoxydans has been recently described as a new arsenite oxidizing bacterial species. Arsenite detoxification activity by this species was determined by HPLC/HG/AAS. P. arsenicoxydans showed a high rate of As(III) conversion, particularly when immobilized (it oxidizes 100 % of 500 µg arsenite present in the medium after 48 of incubation). Arsenite oxidizing activity, mediated by a constitutive periplasmic enzyme, was determined following the transfer of reducing equivalents from arsenite to 2,4-dichlorophenolindophenol (DCIP) showing that approximately 75 % (0.173 µmol DCIP min(-1) mg(-1)) of the total activity (0.231 µmol DCIP min(-1) mg(-1)) was detected in the periplasmic fraction. Using PCR with primers specific for arsenite oxidase gene showed the presence of a gene encoding for arsenite oxidase in P. arsenicoxydans. Results show the potential biotechnological application of P. arsenicoxydans as a candidate for detoxification of As(III).
Assuntos
Arsenitos/metabolismo , Poluentes Ambientais/metabolismo , Pseudomonas/metabolismo , Zeolitas/química , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Dados de Sequência Molecular , Oxirredução , Oxirredutases/genética , Oxirredutases/metabolismo , Pseudomonas/genética , Análise de Sequência de DNARESUMO
The Patagonian Lakes have particular environmental conditions with or without intermittent disturbances. The study of the microorganisms present in aquatic ecosystems has increased notably because they can be used as micro-scale bioindicators of, among others, anthropogenic pollution and climatic change. The aim of the work was to compare the composition of the bacterial communities associated with sediments of three Patagonian Lakes with different geomorphologic patterns and disturbances. The lake sediments were characterized by molecular techniques, physiology profiles and physico-chemical analyses. The metabolic and physiological profiles of the microbial community demonstrated that non-impacted Tranquilo Lake is statistically different to impacted Bertrand and Plomo Lakes. Similar results were detected by DGGE profiles. FISH results demonstrated that betaproteobacteria showed the highest count in the Tranquilo Lake while gammaproteobacteria showed the highest counts in the Bertrand and Plomo Lakes, indicating that their sediments are highly dystrophic. The results demonstrate differences in the metabolic activity and structural and functional composition of bacterial communities of the studied lakes, which have different geomorphological patterns due to disturbances such as volcanic activity and the climatic change.
Assuntos
Bactérias/classificação , Bactérias/metabolismo , Biota , Lagos/microbiologia , Bactérias/genética , Chile , Eletroforese em Gel de Gradiente Desnaturante , Sedimentos Geológicos/microbiologia , Hibridização in Situ FluorescenteRESUMO
A Gram-negative, arsenite-oxidizing bacterial strain, designated VC-1, was isolated from sediment samples from the Camarones Valley in the Atacama Desert, Chile. Strain VC-1 was strictly aerobic, oxidase and catalase positive, rod shaped, of about 5.5 microm in length and 0.5-1.0 microm in diameter. It was motile by means of multiple polar flagella. The phylogenetic reconstruction of the 16S rRNA gene sequence, an MLSA study by concatenating six genes, and DDH studies indicated that the strain differed genotypically from its closest relatives and was therefore recognized as a new species within the genus Pseudomonas. Phenotypic analysis combining metabolic tests, fatty acid profiles and MALDI-TOF profiles of total cell extracts supported the classification of the new species for which we propose the designation Pseudomonas arsenicoxydans sp. nov. The type strain is accessible under the culture collection numbers CCUG 58201(T) and CECT 7543(T).
Assuntos
Arsenitos/metabolismo , Pseudomonas/classificação , Pseudomonas/isolamento & purificação , Microbiologia do Solo , Aerobiose , Proteínas de Bactérias/metabolismo , Técnicas de Tipagem Bacteriana , Catalase/metabolismo , Chile , Análise por Conglomerados , Impressões Digitais de DNA , DNA Bacteriano/química , DNA Bacteriano/genética , DNA Ribossômico/química , DNA Ribossômico/genética , Flagelos/fisiologia , Locomoção , Dados de Sequência Molecular , Oxirredução , Oxirredutases/metabolismo , Filogenia , Pseudomonas/genética , Pseudomonas/fisiologia , RNA Ribossômico 16S/genética , Análise de Sequência de DNARESUMO
This paper presents experimental results on the imidacloprid removal from wastewater using homogeneous photo-Fenton reactions illuminated with black light lamps. Multivariate experimental design was used to identify the effect of initial Fe(II) and H(2)O(2) concentrations on process performance. The initial iron concentration played a key role in the process kinetics, whereas hydrogen peroxide concentration directly affected the extent of the oxidation process. Imidacloprid degradation proceeded via two distinctive kinetics regimes, an initial stage of rapid imidacloprid reduction, followed by a slower oxidation process until complete removal. Under optimal conditions, more than 50% imidacloprid degradation was observed after less than 1 min treatment, and TOC and COD removal up to 65% and 80%, respectively, were measured after all hydrogen peroxide was consumed. Raw imidacloprid samples presented significant acute toxicity to Daphnia magna and genotoxic effects on Bacillus subtilis sp. Such toxic effects remained detectable even after significant pesticide removal had been achieved, due to the presence of toxic by-products. Both acute toxicity and genotoxicity disappeared after considerable mineralization resulting in final low molecular weight by-products. Results obtained here confirm that design and operation of photo-Fenton processes should focus on toxicity removal rather than on specific target pollutants.
Assuntos
Imidazóis/química , Imidazóis/efeitos da radiação , Inseticidas/química , Inseticidas/efeitos da radiação , Nitrocompostos/química , Nitrocompostos/efeitos da radiação , Raios Ultravioleta , Poluentes Químicos da Água/química , Poluentes Químicos da Água/efeitos da radiação , Purificação da Água/métodos , Animais , Bacillus subtilis/efeitos dos fármacos , Bacillus subtilis/genética , Dano ao DNA , Daphnia/efeitos dos fármacos , Peróxido de Hidrogênio/química , Imidazóis/toxicidade , Inseticidas/toxicidade , Ferro/química , Dose Letal Mediana , Neonicotinoides , Nitrocompostos/toxicidade , Oxirredução , Fotoquímica , Poluentes Químicos da Água/toxicidadeRESUMO
Effluents from small and medium sized chemical plants may contain significant amounts of poorly biodegradable aromatic compounds, which could negatively affect water quality and public health. This is a key environmental issue, particularly in areas where effluents are discharged into drinking water sources. Unfortunately, conventional biological treatment may not be able to meet discharge standards, and combined systems should be implemented. In this context, this paper presents experimental results on the application of a combined sequential ozonation-activated carbon-biological system to treat effluents containing chlorinated aromatic contaminants from chlorine based pulp bleaching. The experimental system consisted of an ozone bubble column reactor (0.3 dm3), an activated carbon fixed bed reactor (0.2 dm3), and an aerobic bioreactor (20 dm3). Ozone was produced from pure O2 using a generator rated at 2 mmol O3 h(-1). The bleaching effluent was pretreated and fed into the aerated sequencing batch bioreactor containing preconditioned biological sludge (3-4 g VSS dm(-3)), and cultured for 24 h. Samples of raw and treated effluents were assayed for biochemical oxygen demand (BOD5), chemical oxygen demand (COD), total organic carbon (TOC), total phenols, and adsorbable organic halogens (AOX), using standard techniques. The presence of potential genotoxic activity in untreated and treated samples was assessed using the Ames tests. Results show that biological treatment of raw samples could not remove mutagenic activity on its own. On the other hand, ozonation followed by activated carbon treatment and biological treatment successfully removed genotoxicity in all cases. Reductions in BOD, COD, TOC, AOX, and phenols by biological treatment increased when samples were pretreated with ozone/activated carbon.