Daniel Derrossi Meyer

Capability of a selected bacterial consortium for degrading diesel/biodiesel blends (B20): Enzyme and biosurfactant production

The search for alternative sources of energy, such as biodiesel, has been stimulated, since this biofuel is highly susceptible for biodegradation and has low toxicity, thus, reducing the impact in ecosystems. The objective of this study was to select a bacterial consortium with potential for degrading diesel/biodiesel blends (B20) obtained from areas contaminated with hydrocarbons/esters. In order to evaluate the biodegrability of the blend, six enzyme assays were conducted: alkane hydroxylase, Catechol 1,2-dioxygenase, Catechol 2,3-dioxygenase, Protocatechol 3,4-dioxygenase, ρ-NPA hydrolysis (esterase), and release of fatty acids through titration (lipase), with estimative of total protein and biosurfactant production (surface tension measurement and emulsifying index E24). The best results obtained allowed the selection of four bacteria isolates (Bacillus megaterium, Bacillus pumilus, Pseudomonas aeruginosa, and Stenotrophomonas maltophilia) for compiling a consortium, which will be used for bioaugmentation strategies in soils contaminated with these fuels. This consortium exhibited high potential for biodegradation of biodiesel, and might be an efficient alternative for cleaning up these contaminated environments.

Simulation of a surface spill of different diesel/biodiesel mixtures in an ultisol, using natural attenuation and bioaugmentation/biostimulation

Accidents caused by leaks and/or spills on soils need to be addressed. Natural attenuation, biostimulation and bioaugmentation can be useful bioremediation strategies for decontamination processes in soils of diesel/biodiesel mixtures. The purpose of this study was to evaluate the degradation rate of the different fuels (B0, B20 and B100) in an ultisol under natural attenuation and biostimulation/bioaugmentation during 60 days of incubation in a controlled microcosm simulating a surface spill over soil. The degradation of different diesel/biodiesel mixtures was monitored for up to 60 days by dehydrogenase activity, respirometry by CO2 release, the most probable number of heterotrophic and degrading microorganism and gas chromatography. The bacterial inoculum employed for biostimulation/bioaugmentation strategy consisted of Bacillus megaterium, Bacillus pumilus, Pseudomonas aeruginosa, and Stenotrophomonas maltophilia. The two bioremediation strategies have showed great degradation rates. The natural attenuation was effective for B0 and B20 treatments. The addition of the bacterial consortium and macronutrients contributed to the increased degradation of pure biodiesel in relation to natural attenuation, with higher rates for CO2 release, enzymatic and degrading activity. It is suggested that the bacterial consortium has proven effective for presenting significant values for such parameters until the end of the 60-day incubation period.

Emprego de um software baseado em mineração de texto e apresentação gráfica multirrepresentacional como apoio à aprendizagem de conceitos científicos a partir de textos no Ensino Fundamental

portuguesResumo: Este artigo apresenta dois estudos independentes que tem como objetivo investigar como uma ferramenta baseada em mineracao de texto e apresentacao grafica multirrepresentacional (SOBEK) pode contribuir no processo de construcao de conceitos cientificos por estudantes do Ensino Fundamental. Os estudos foram realizados atraves de pesquisa quasi-experimental com aplicacao de pre-teste e pos-teste, utilizando grupos controle nao equivalentes. Textos refutacionais de pesquisas ja publicadas foram utilizados nas intervencoes, assim como testes de performance correspondentes aos textos. Os conceitos abordados foram energia e natureza particulada da materia. Os estudos foram conduzidos em duas turmas de 9o ano de uma escola municipal no sul do Brasil. Analises estatisticas do desempenho nos testes mostraram melhora significativa dos estudantes que utilizaram o SOBEK como suporte para estudo dos textos. Investigacoes mais detalhadas sao necessarias para identificar a ocorrencia e extensao das modificacoes na estrutura conceitual dos estudantes e sua relacao com a estrategia proposta. EnglishAbstract: This work presents two independent studies that aim to investigate how a tool based on text mining and multi-representational graphical presentation (SOBEK) can contribute to the process of constructing scientific concepts from text by elementary school students. The studies were conducted in a quasi-experimental design with application of pre-test and post-tests with non-equivalent control groups. Refutational texts from published researches were used, as well as the corresponding performance tests about each text. The concepts covered are energy and the particulate nature of matter. Performed in a municipal school in Southern Brazil, the studies included two classes of 8th grade students. Statistical analysis of scores performed by students in tests show significant improvements in students performance that used the SOBEK tool as support for the study of text. More detailed studies are needed to identify the occurrence and extent of possible changes in students´ conceptual structure supported by the proposed approach.

Sulphate production by Paracoccus pantotrophus ATCC 35512 from different sulphur substrates: sodium thiosulphate, sulphite and sulphide

ABSTRACT One of the problems in waste water treatment plants (WWTPs) is the increase in emissions of hydrogen sulphide (H2S), which can cause damage to the health of human populations and ecosystems. To control emissions of this gas, sulphur-oxidizing bacteria can be used to convert H2S to sulphate. In this work, sulphate detection was performed by spectrophotometry, ion chromatography and atomic absorption spectrometry, using Paracoccus pantotrophus ATCC 35512 as a reference strain growing in an inorganic broth supplemented with sodium thiosulphate (Na2S2O3·5H2O), sodium sulphide (Na2S) or sodium sulphite (Na2SO3), separately. The strain was metabolically competent in sulphate production. However, it was only possible to observe significant differences in sulphate production compared to abiotic control when the inorganic medium was supplemented with sodium thiosulphate. The three methods for sulphate detection showed similar patterns, although the chromatographic method was the most sensitive for this study. This strain can be used as a reference for sulphate production in studies with sulphur-oxidizing bacteria originating from environmental samples of WWTPs.