Influência da intensidade de aeração na formação do floco de lodo ativado e na eficiência de remoção de matéria orgânica

In wastewater treatment, activated sludge systems have been a technology widely applied as secondary treatment. During this step, which has a strong biological aspect, it is necessary to introduce oxygen supply for the maintenance of metabolic activity of the bacteria through the aerators. Aeration devices are responsible for most of the energy consumption in this stage. In this background, the influence of three aeration intensities (atmospheric air flow 3.5, 7.0 and 10.5 L.min-1) and the concentration of dissolved oxygen (DO) on the dimension of activated sludge flocs as well as on the efficiency of organic matter removal were assessed using a traditional activated sludge system which was fed with synthetic domestic wastewater. Samples were taken weekly from the three units that make up the system feed, aeration and storage tank in order to verify the Chemical Oxygen Demand (COD). It was established the process efficiency through a comparison between the initial and final COD. Besides the parameters already mentioned, this monitoring work on activated sludge batch system was also observed by Mixed Liquor Suspend Solids (MLSS), Volatile Suspend Solids (VSS), pH and temperature measures. The results have showed a maximum removal efficiency around 75% in the first aeration sequence and approximately 85% for the second and third one. For the first aeration, the DO concentration remained higher than 3.0 mg.L-1 and a diameter range from 10 to 60 μm was observed. In the second e third sequence, the DO concentration remained higher than 4.0 mg.L-1 with a diameter range of 10 until 200 μm. Although the sequence 1 and 2 have presented similar performances for organic matter removal, the sequence 2 promoted a regular floc size distribution and with lower values of Sludge Volumetric Index (SVI) meaning a better flocculating ability. In addition, the results reaffirmed what the literature has reported: higher DO concentrations produce flocs with greater dimensions

Levantamento e avaliação de critérios para a ampliação de escala da produção de biossurfactantes utilizando melaço como substrato

Biosurfactants are amphiphilic molecules synthesized by microorganisms such as bacteria, yeast or filamented fungi cultivated in various carbon sources among sucrose and hydrocarbons. These molecules are composed by a hydrophilic and hydrophobic part. They operate mostly at interfaces of fluids of different polarities. Because of this characteristic, they are potentially employed in numerous industries, such as the textile, medical, cosmetics, food and mainly in the petrochemical ones. Therefore industry has interest in developing new biosurfactant production processes in high scale, in order to become them economically competitive when compared to synthetic biosurfactants. This work aims to evaluate the biosurfactant production applying a non-conventional substrate sugar cane molasses proceeding from the sugar industry thus reducing the production costs. The strain identified as AP029/GLIIA, isolated from oil wells in Rio Grande do Norte state and used in these experiments belongs to the culture collection of Antibiotics Department of UFPE. The fermentation were carried out using different conditions according to a factorial planning 24 with duplicate at center point, in which the studied factors were molasse concentration, nitrate concentration, agitation and aeration ratio. The experiments were performed in a shaker at 38ºC of temperature. Samples were withdrawn in regular periods of time of up to 72 hours of fermentation in order to analyze substrate consumption, cellular concentration, superficial tension, critical micelle dilution (CMD-1 e CMD-2) as well as extracelullar protein production. The results showed a production of 3,480 g/L of biomass, a reduction of 41% on superficial tension, 67% of substrate consumption and 0,2805 g/L of extracellular protein

Recuperação e purificação de ramnolipídeos produzidos por pseudomonas aeruginosa P029-GVIIA utilizando melaço de cana como substrato

Biosurfactants are molecules produced by microorganisms mainly bacteria as Pseudomonas and Bacillus. Among the biosurfactants, rhamnolipids play an important role due to their tensoactive as well as emulsifying properties. Besides can be produced in a well consolidated way the production costs of biosurfactants are quite expansive mainly if downstream processing is goning to be considered. Actually, attention has been given to identification of biosurfactants as well as optimization of its fermentative processes including downstream ones. This work deals with the development of strategies to recovery and purification of rhamnolipids produced by Pseudomonas aeruginosa P029-GVIIA using sugar-cane molasses as substrate. Broth free of cells was used in order to investigate the best strategies to recovery and purification produced by this system. Between the studied acids (HCl and H2SO4) for the acid precipitation step, HCl was the best one as has been showed by the experimental design 24. Extraction has been carried out using petroleum ether and quantification has been done using the thioglycolic acid method. Adsorption studies were carried out with activated carbon in a batch mode using a 24 experimental design as well as combined with an hydrophobic resin Streamline Phenyl aiming to separate the produced biosurfactant. Biosurfactant partial identification was carried out using High Performance Liquid Chromatography (HPLC). Experiments in batch mode showed that adsorption has been controlled mainly by pH and temperature. It was observed a reduction of 41.4% for the liquid phase and the solid phase it was possible to adsorb up to 15 mg of rhamnolipd/g of activated carbon. The kinetics of adsorption has been well fitted to a pseudo-first order reaction with velocity constant (k1) of 1.93 x 10-2 min-1. Experiments in packed bed ranging concentration on eluent (acetone) has been shown the highest recovery factor of 98% when pure acetone has been used. The combined effect if using activated carbon with an hydrophobic resin Streamline Phenyl has been shown successful for the rhamnolipids purification. It has been possible to purify a fraction of the crude broth with 98% of purity when the eluted of activated carbon packed bed was used with pure acetone

Decaimento bacteriano em lagoas de estabilização no Nordeste brasileiro

Stabilization pond system consisting in more sewage treatment used in Rio Grande do Norte (RN), Brazil, representing about 90% of all systems. Fecal bacteria are removed mainly facultative ponds and in maturation ponds. Many factors influence bacterial decay, such as the levels of pH and DO, temperature, light intensity, HDT and nutrient availability. The bacterial decay rate (Kb) is calculated considering many variables, but the hydraulic regime is a significant influence for microorganisms removal, and the dispersed flow which best characterizes a stabilization pond. However, some authors developed equations for the Kb accordant plug flow and complete mixing. This research study aimed to evaluate the bacterial decay of fecal coliform and Enterococcus sp. in stabilization ponds designed to treat domestic sewage, full-scale, in RN. All systems have assessed pretreatment, a facultative pond (LF) followed by two maturation (LM1 and LM2). The parameters availed were: temperature, pH, DO, BOD5, COD, fecal coliform, Enterococcus sp., Chlorophyll a, total suspended solids, fixed and volatile. In general, there were not significant differences for pH, DO and temperature in the ponds, except for the new systems, since they have low flow and hydraulic loads. The removal of organic matter in the ponds was low, about 70%, and nearly all are overloaded organic and operational problems. The bacterial removals were low, with average 96% for LF for fecal coliform, and 98% for Enterococcus sp.; LM1 were in itself a removal for fecal coliform about 71%, and 81% for Enterococcus sp.; LM2 have efficiency of 69% for fecal coliform, and 68% for Enterococcus sp. The equation proposed by Von Sperling (1999), according to the dispersed flow regime, generated empirical values of Kb more approximate to calculated values of Kb. On average, the calculated Kb to coliforms in the LF was 0.31 d-1, and for both maturation ponds were 0.35 d-1. For Enterococcus sp. the average was 0.40 d-1 for LF, 0.55 d-1 for LM1, and 0.58 d-1 for LM2. These results also showed that the Kb obtained in full-scale systems are smaller than those found in pilot-scale ponds. Moreover, one can say that the equation proposed by Marais (1974), according to the complete-mix regime, overestimates Kb. Actual results of Kb indicated that fecal coliforms are more resistant to adverse conditions present in stabilization ponds than Enterococcus sp., therefore, an indicator of microbiological safety and efficiency. The factors significant interventions in the rate of bacterial decay were concentrations of COD, the organic loading and HDT. The few Kb relationship between pH, DO and temperature were not significant. Finally, we conclude that it s essential to correct operation and maintenance, for not performing these activities is one of the main factors contributing to low rates of bacterial decay.

O que controla o crescimento do Fitoplâncton em lagoas costeiras tropicais? um modelo para a lagoa de Extremoz (RN)

The phytoplankton growth is dependent of several abiotic (nutrients, temperature) and biotic (predation by zooplankton) variables. In this work, a mathematical model was developed in Stella software to understand the planktonic dynamics of Extremoz Lagoon (RN) and to simulate scenarios of different environmental conditions. Data were collected monthly at two points of the lagoon. The state variables are phytoplankton and zooplankton and forcing variables are nitrogen, phosphorus and temperature. The results show that: a) the model are well coupled, especially when some constants assume different values; b) simulated nutrient concentrations reduction decreases phytoplankton biomass, but the increase of nutrients does not stimulate the growth; c) changes in the temperature does not change the phytoplankton biomass; d) changes in zooplankton biomass affect directly and reduces the phytoplankton, indicating a topdown control mechanism; e) changes in the nutrient concentration modified the biomass of zooplankton suggesting a rapid flow of energy between nutrients, phytoplankton and zooplankton and a ecosystem likely arranged in an inverted pyramid (higher concentration of zooplankton than phytoplankton)

Evolução do reparo por excisão de nucleotídeo

The phylogeny is one of the main activities of the modern taxonomists and a way to reconstruct the history of the life through comparative analysis of these sequences stored in their genomes aimed find any justification for the origin or evolution of them. Among the sequences with a high level of conservation are the genes of repair because it is important for the conservation and maintenance of genetic stability. Hence, variations in repair genes, as the genes of the nucleotide excision repair (NER), may indicate a possible gene transfer between species. This study aimed to examine the evolutionary history of the components of the NER. For this, sequences of UVRA, UVRB, UVRC and XPB were obtained from GenBank by Blast-p, considering 10-15 as cutoff to create a database. Phylogenetic studies were done using algorithms in PAUP programs, BAYES and PHYLIP package. Phylogenetic trees were build with protein sequences and with sequences of 16S ribosomal RNA for comparative analysis by the methods of parsimony, likelihood and Bayesian. The XPB tree shows that archaeal´s XPB helicases are similar to eukaryotic helicases. According to this data, we infer that the eukaryote nucleotide excision repair system had appeared in Archaea. At UVRA, UVRB and UVRC trees was found a monophyletic group formed by three species of epsilonproteobacterias class, three species of mollicutes class and archaeabacterias of Methanobacteria and Methanococci classes. This information is supported by a tree obtained with the proteins, UVRA, UVRB and UVRC concatenated. Thus, although there are arguments in the literature defending the horizontal transfer of the system uvrABC of bacteria to archaeabacterias, the analysis made in this study suggests that occurred a vertical transfer, from archaeabacteria, of both the NER genes: uvrABC and XPs. According the parsimony, this is the best way because of the occurrence of monophyletic groups, the time of divergence of classes and number of archaeabacterias species with uvrABC system

Análise comparativa dos genes de reparo do DNA em Gluconacetobacter diazotrophicus e Gluconobacter oxydans

Gluconacetobacter diazotrophicus é uma alfa-proteobactéria Gram-negativa, tolerante a meios ácidos, fixadora de nitrogênio atmosférico e foi a primeira bactéria diazotrófica endofítica isolada da cana-de-açúcar. Por sua vez, Gluconobacter oxydans, também alfa-proteobactéria Gram-negativa, possui a capacidade de oxidar incompletamente alcoóis e carboidratos. Ambas de interesse biotecnológico e industrial, essas bactérias tiveram seus genomas seqüenciados completamente em 2007. Desta forma, foi de interesse desse trabalho analisar e comparar os genes de reparo do DNA devido sua importância na manutenção da integridade genômica. Sendo assim, as vias de reparo presentes nos dois organismos foram identificadas, utilizando como base uma terceira alfa-proteobactéria, a Caulobacter crescentus, cujos genes de reparo foram descritos por um trabalho anterior e também os genes bem estabelecidos para o reparo do DNA em Escherichia coli. Para esse estudo, um banco de dados contendo ortólogos para os genes de reparo de DNA encontrados nos organismos foi criado e análises comparativas por similaridade usando o pacote Blast e o software Clustal foram feitas. Este estudo demonstrou que as principais vias de reparo ao DNA reparos por excisão, reparo direto, reparo recombinacional e reparo pelo sistema SOS estão presentes nos organismos analisados, demonstrando, na maioria das vezes, boa similaridade com E. coli. Interessantemente, foram encontradas duplicações gênicas nos quais uma das cópias estava presente no cromossomo e a outra, no plasmídeo, como no caso de UvrD, DnaE e Ssb, possivelmente caracterizando eventos de transferência lateral. Por fim, uma grande novidade foi a identificação de ortólogos para RecB em G. diazotrophicus e G. oxydans e de ortólogos duplicados de RecD em G. diazotrophicus. Até o momento, não havia sido relatada a presença de membros da via de iniciação RecBCD do reparo recombinacional em alfaproteobactérias

Estudos ecogenômicos e bioprospectivos de Shewanella ssp

Bacteria trom Shewanella and Geobacter ganera are the most studied iron-reducing microorganisms particularly due to their electron transport systems and contribution to some industrial and environmental problems, including steel corrosion, bioenergy and bioremediation of petroleum-impacted sites. The present study was focused in two ways: the first is an in silico comparative ecogenomic study of Shewanella spp. with sequenced genomes, and the second is an experimental metagenomic work to detect iron-reducing Shewanella through PCR-DGGE of a metabolic gene. The in silico study resulted in positive correIation between copy number of 16S rDNA and genome size in Shewanella spp., with clusters of rrn near lhe origin of replication. This way, the genus is inferred as opportunist. There are no compact genomes and their sequences length varied, ranging from 4306142 nt in S. amazonensis SB2B to 5935403 nt in S. woodyi ATCC 51908, without correIation to temperature range characteristic of each specie. Intragenomic 16S rDNA sequences possess little divergence, but reasonable to resuIt in different phyIogenetic trees, depending on the sequence that is chosen to compare. For moIecuIar detection of iron-reducing Shewanella, it is proposed the mtrB gene as new biomarker. because it codes to a fundamental protein at Fe (III)-reduction. The specific primers were designed and evaluated in silico and resulted in a fragment of 360 pb. In the second study, these primers were tested in a genomic sample from S. oneidensis MR-1, amplifying the expected region. After this successfuI resuIt, the primer set was used as a tool to assess the iron-reducing communities of ShewaneIla genus under an environmental stress, i.e. crude oil contamination in mangrove sediment in Rio Grande do Norte State (Brazil). The primers presented high specificity and the reactions performed resulted in one single band of ampIification in the metagenomic samples. The fingerprinting obtained at DGGE reveaIed temporal variation of Shewanella spp. in analyzed samples. The resuIts presented show the detection of a biotechnological important group of microorganisms, the iron-reducing Shewanella spp. using a metabolic gane as target. It is concluded there are eight or more 16S rDNA sequences in Shewanella genus, with little divergence among them that affects the phylogeny; the pair of primers designed to ampIify mtrB sequences is a viable alternative to detect iron-reducing ShewanelIa in metagenomic approaches; such bacteria are present in the mangrove sediment anaIyzed, with temporal variations in the samples. This is the first experimental study that screened the iron-reducing Shewanella genus in a metagenomic experiment of mangrove sediments subjected to oil contamination through a key metabolic gene

Análise imuno-histoquímica das metaloproteinases da matriz ( MMP-1,MMP-2 e MMP-9) na doença periodontal

The tissular destruction found in periodontal diseases is caused mainly by components of the host that have its production stimulated by the products of the microorganisms present on the plaque. Matrix Metalloproteinases (MMPs), a class of enzymes involved both in physiologic and pathologic extracellular matrix degradation are considered the main responsible for the characteristic tissular loss in periodontal disease, and the understanding of how this happens can have a series of beneficial implications for prevention, diagnosis and treatment of this illness. The aim of this work was to study the immunohistochemical expression of MMP-1, MMP-2, and MMP-9 in fragments of gingival biopsies with clinical diagnose of periodontal disease. MMP-1 has expressed significantly more than the others MMPs in gingivitis both in the epithelium (p=0,0008) and connective tissue (p=0,0049). In periodontitis, both MMP-1 and MMP-9 has expressed significantly more than MMP-2 in the epithelium (p<0,0001) and in the connective tissue (p=0,0002). MMP-1 and MMP-9 presented more expression in periodontitis than in gingivitis but MMP-1 only in the connective tissue (p=0,03) and MMP-9 in the epithelium (p=0,003) and in the connective tissue (p=0,04). In conclusion, these results indicate that the MMP-1 presents high expression in every stages of the periodontal diseases, and increases its expression in the connective tissue when the gingivitis evolves to periodontitis. Therefore, it may have an important role in connective tissue degradation and bone loss observed in disease, since early, in gingivitis, until late stages, in periodontitis, of the periodontal disease. MMP-9 has expressed more in periodontitis than in gingivitis, both in epithelium and in connective tissue. It means that this enzyme may have some importance in the progression of gingivitis to periodontitis by acting in bone resorption observed in this desease

Obtenção de sistemas microemulsionados e estudo de simulação por dinâmica molecular de sistemas micelares objetivando a veiculação de produtos naturais bioativos

Among the new drugs launched into the market since 1980, up to 30% of them belong to the class of natural products or they have semisynthetic origin. Between 40-70% of the new chemical entities (or lead compounds) possess poor water solubility, which may impair their commercial use. An alternative for administration of poorly water-soluble drugs is their vehiculation into drug delivery systems like micelles, microemulsions, nanoparticles, liposomes, and cyclodextrin systems. In this work, microemulsion-based drug delivery systems were obtained using pharmaceutically acceptable components: a mixture Tween 80 and Span 20 in ratio 3:1 as surfactant, isopropyl mirystate or oleic acid as oil, bidistilled water, and ethanol, in some formulations, as cosurfactants. Self-Microemulsifying Drug Delivery Systems (SMEDDS) were also obtained using propylene glycol or sorbitol as cosurfactant. All formulations were characterized for rheological behavior, droplet size and electrical conductivity. The bioactive natural product trans-dehydrocrotonin, as well some extracts and fractions from Croton cajucara Benth (Euphorbiaceae), Anacardium occidentale L. (Anacardiaceae) e Phyllanthus amarus Schum. & Thonn. (Euphorbiaceae) specimens, were satisfactorily solubilized into microemulsions formulations. Meanwhile, two other natural products from Croton cajucara, trans-crotonin and acetyl aleuritolic acid, showed poor solubility in these formulations. The evaluation of the antioxidant capacity, by DPPH method, of plant extracts loaded into microemulsions evidenced the antioxidant activity of Phyllanthus amarus and Anacardium occidentale extracts. For Phyllanthus amarus extract, the use of microemulsions duplicated its antioxidant efficiency. A hydroalcoholic extract from Croton cajucara incorporated into a SMEDDS formulation showed bacteriostatic activity against colonies of Bacillus cereus and Escherichia coli bacteria. Additionally, Molecular Dynamics simulations were performed using micellar systems, for drug delivery systems, containing sugar-based surfactants, N-dodecylamino-1-deoxylactitol and N-dodecyl-D-lactosylamine. The computational simulations indicated that micellization process for N-dodecylamino-1- deoxylactitol is more favorable than N-dodecyl-D-lactosylamine system.

Uso da espectroscopia do infravermelho próximo e técnicas multivariadas para diferenciar escherichia coli e salmonella enteritidis inoculadas em polpa de fruta (abacaxi)

Aiming to consumer s safety the presence of pathogenic contaminants in foods must be monitored because they are responsible for foodborne outbreaks that depending on the level of contamination can ultimately cause the death of those who consume them. In industry is necessary that this identification be fast and profitable. This study shows the utility and application of near-infrared (NIR) transflectance spectroscopy as an alternative method for the identification and classification of Escherichia coli and Salmonella Enteritidis in commercial fruit pulp (pineapple). Principal Component Analysis (PCA), Independent Modeling of Class Analogy (SIMCA) and Discriminant Analysis Partial Least Squares (PLS-DA) were used in the analysis. It was not possible to obtain total separation between samples using PCA and SIMCA. The PLS-DA showed good performance in prediction capacity reaching 87.5% for E. coli and 88.3% for S. Enteritides, respectively. The best models were obtained for the PLS-DA with second derivative spectra treated with a sensitivity and specificity of 0.87 and 0.83, respectively. These results suggest that the NIR spectroscopy and PLS-DA can be used to discriminate and detect bacteria in the fruit pulp

Usos e qualidade da água em região semi-árida do nordeste brasileiro: percepção ambiental de professores e alunos

Density and biomass of bacterioplankton in parts of the Marechal Dutra reservoir were studied in periods of dry and rainy season. The averages of the total bacterial densities oscillated in the order of 107 organisms/ mL of sample. The cocci cells were numerically predominant, influencing considerably the total abundance of the bacterioplankton. The total bacterial biomass, was considered raised and varied from 2.431,82 to 2.739,01 μgC.L-1, in function of the high values of biovolume of the filaments forms, and showed no marked spacial fluctuation. These high values of density and biomass alert for the necessity of a frequent monitoring of aquatic ecosystems of semi-arid region, where the quality of the water is affected by the occurrence of extensive dry periods, influencing considerably the quality of life of its population

Protozoários de vida livre em ambientes aquáticos do RN: ocorrência, caracterização e importância para a educação básica

Water is considered an essential right to life, besides being a determinant of economic development and social welfare, represented by both the quantity available, and the quality. In semi-arid Northeast, droughts occurring on a regular basis combined with human activities, aggravate the situation regarding the conservation of water resources in this area. To alleviate this condition is common to construction of artificial reservoirs, such as reservoirs and dams. As in natural aquatic environments, these reservoirs are potential sites for the proliferation, growth and development of diverse biological communities, whether of animals, plants and microorganisms. Research on the composition and ecology of these communities, especially microbial, are still restricted. One of the least studied groups in these environments are free-living protozoa, which over time have been neglected and after discoveries about its various functions in the aquatic ecosystem are beginning to receive more attention from scholars. They are, in quantitative terms, the most important consumers of microorganisms (mainly bacteria and algae) in aquatic environments, and therefore control the abundance of these. They may therefore influence the structure of the aquatic food chain in terms of species composition, abundance, biomass and biodiversity. Despite the recognition of the importance of protozoa in the final of the trophic transfer in aquatic environments, there are few data and, in general, are still precarious knowledge of them. Given the importance of protozoa in aquatic environments and the paucity of research on this group, especially in the state of Rio Grande do Norte, the present study aimed at identifying the genus and species of free-living protozoa that are present in the Armando Ribeiro Gonçalves Dam as well as to relate the occurrence and dynamics of the trophic conditions in the environment in which they are inserted, in order to support the hypothesis that species that are in these environments can serve to indicate the water quality. We observed the presence of 65 taxa of free-living protozoa, of which 29 were identified at the species level. There was a similarity space in taxonomic composition of protozoa, suggesting a possible regulation of this type of community for limnological variables other than those studied in this work (chlorophyll a, pH, temperature). Although it was aimed to analyze the conceptions of teachers and students from nearby towns Dam Armando Ribeiro Gonçalves, on issues relating to water quality and the role of protozoa. For this, we applied questionnaires with teachers and pupils of public schools of San Rafael and Itajá. It was concluded that teachers and students recognize the multi-dam Armando Ribeiro Gonçalves, although unaware of important aspects of the dynamics and ecology of this environment. Conceptions of teachers and students are matched at various times, especially with regard to waterborne diseases. In an attempt to identify possible misconceptions about the knowledge of the protozoa, assuming that these organisms have neglected their ecological role, and are seen as only, disease, a study was done with teachers and students, following a particular methodology that allowed look so clear and precise results. It was clear that knowledge about the free-living protozoa is still quite limited. The alternative conceptions that were found show a direct relation of protozoans and diseases. From the data obtained by these studies, we planned a series of science communication activities, environmental education and health education in schools close to study environments in order to promote a didactic transposition of accumulated knowledge about these organisms, favoring continuing education of teachers and the increase of information to the local community through the knowledge of biodiversity and ecology of these organisms. Moreover, the results found in this study and reflections on it that led to propose the elaboration of a book Readers with an emphasis on the group of freeliving protozoa in the populations for use in public schools in the region where it was developed the semiarid work

Avaliação do caráter oxidante da violaceína

Violacein is a violet pigment isolated from many gram-negative bacteria, especially from Chromobacterium violaceum, a betaproteobacterium found in the Amazon River in Brazil. It has potential medical applications as an antibacterial, fungicide, anti-tryptanocidal, anti-ulcerogenic and anti-cancer drug, among others. Furthermore, its pro-oxidant activity has been suggested, but only in two specific tumor lineages. Thus, in the present study, the prooxidant effects of violacein were investigated in both normal and tumor cells, seeking to evaluate the cell responses. The evaluation of violacein cytotoxicity using the Trypan blue dye exclusion method indicated that CHO-K1 cells were more resistant than tumor HeLa cells. The oxidative stress induced by violacein was manifested as an increase in intracellular SOD activity in CHO-K1 and MRC-5 cells at a specific concentration range. Nevertheless, a decrease was detected specifically at 6-12 μM in HeLa and MRC-5 cells. Interestingly, the increase in SOD activity was not followed by a concomitant increase in catalase activity. Regarding to oxidative stress biomarkers, increased protein carbonylation and lipid hydroperoxides levels were detected respectively in CHO-K1 and MRC-5 cells treated with violacein at 1.5-3 μM and 3 μM, which may be an evidence that this compound causes oxidative stress specifically in these conditions. Additionally, it is believed that the decline in cell viability observed in MRC-5 cells and HeLa treated with violacein at 6-12 M is due to mechanisms not related to oxidative stress. Moreover, the results suggested that violacein might cause oxidative stress by increasing endogenous levels of O2 -, since the occurrence of an expressive change in SOD activity. In addition, in order to evaluate the antioxidant activity of violacein in the absence of a biological system, the total antioxidant and iron chelating activity were evaluated, so that antioxidant activities were detected at 30 and 60 μM of violacein. Altogether, the results indicate that although oxidative stress is triggered by incubation with violacein, it did not seem to be high enough to cause serious damage to cell biomolecules in HeLa cells and only at specific concentrations in CHOK-1 and MRC-5 cells. Comparing the results obtained in cell culture and the in vitro antioxidant activity evaluation, the results confirmed that violacein presents opposing oxidant features when in presence or absence of a biological system and the antioxidant character only occurs at high concentrations of the pigment.