Microbial activity in two soils with different clay content contaminated by different diesel/biodiesel mixtures

Biodiesel is an alternative energy source that has a high biodegradability potential and low toxicity, contributing to ecosystem impact reductions. The aim of this study was to determine, by the natural attenuation technique, the microbial activity of two soils: one clayey (CLA) and the other sandy (SAN), contaminated with different concentrations of biodiesel blended with diesel (B0, B5, B20 and B100) simulating a surface spill. The respirometry, fluorescein diacetate (FDA) hydrolysis and cultivable heterotrophic bacteria and actinobacteria count techniques were used to determine the microbial activity in the different microcosms at up to 48 days of incubation. For the respiration activity, the CLA soil was most active at all mixed fuel concentrations (B0, B5, B20 and B100), as compared to the SAN. Furthermore, the biodiesel addition to the two soil types contributed to the microbial activity increase, and higher CO2 release values were found in the B20 and B100. For the FDA activity, it was found that the CLA soil showed higher activity at the B5 and B20 concentrations, and heterotrophic count showed a tendency towards a CFU g-1 decrease as the incubation time increased. This indicates that the CLA soil, due to a higher amount of nutrients, clay, organic matter and CEC, was associated with the addition of biodiesel and showed higher microbial activity. The results obtained in this study contribute to future studies of surface contamination by different mixtures of diesel/biodiesel in soils with similar physical and chemical characteristics

Purification and characterization of a thermostable alkaline cellulase produced by Bacillus licheniformis 380 isolated from compost

During composting processes, the degradation of organic waste is accomplished and driven by a succession of microbial populations exhibiting a broad range of functional competencies. A total of 183 bacteria, isolated from a composting process, were evaluated for cellulase activity at different temperatures (37, 50, 60, and 70°C) and pH values. Out of the 22 isolates that showed activity, isolate 380 showed the highest cellulase activity. Its ability to produce cellulase was evaluated in culture medium supplemented with carboxymethyl cellulose, microcrystalline cellulose, wheat straw, and rice husk. The culture medium supplemented with carboxymethyl cellulose induced higher enzyme activity after 6 hours of incubation (0.12 UEA mL-1 min-1). For wheat straw and rice husk, the results were 0.08 UEA mL-1 min-1 for both, while for microcrystalline cellulose, 0.04 UEA mL-1 min-1 were observed. The highest carboxymethyl cellulase activity was observed at 60°C (0.14 UEA mL-1 min-1) for both crude and partially purified enzyme after 30 and 120 min of incubation, respectively. Alkalinization of the medium was observed during cultivation in all substrates. The cellulase had a molecular mass of 20 kDa determined by SDS-Page. Isolate 380 was identified as Bacillus licheniformis. This work provides a basis for further studies on composting optimization

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

A GERAÇÃO DE RESÍDUOS SÓLIDOS POR CURTUMES E ALTERNATIVAS DE TRATAMENTO E REÚSO

As atividades industriais geram resíduos de formas variadas que, predominantemente, apresentam um elevado grau de poluição, tendo, na maioria das vezes, os aterros industriais como disposição final. A indústria do couro é uma grande geradora de resíduos industriais, os quais apresentam volume residual da pele e de cromo, do couro curtido e do tratamento dos efluentes gerados durante a produção. Aterrar resíduos de curtume, além de um potencial risco de contaminação ambiental, gera gastos e resulta em desperdício de material potencialmente reaproveitável. Diante da necessidade de alerta e alternativas ao aterramento desses resíduos, tratamentos para a remoção do cromo, através de processos físico-químicos e biológicos, são indicados para o reaproveitamento do material. O objetivo deste trabalho foi revisar a literatura científica em busca das informações consagradas sobre as diferentes metodologias aplicadas na recuperação do resíduo. Há uma inclinação pela adoção de técnicas que removem o cromo de efluentes e do lodo de curtume para seu melhor reaproveitamento e incorporação em diversos setores produtivos

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

Este artigo apresenta dois estudos independentes que têm como objetivo investigar como uma ferramenta baseada em mineração de texto e apresentação gráfica multirrepresentacional (SOBEK) pode contribuir no processo de construção de conceitos científicos por estudantes do Ensino Fundamental. Os estudos foram realizados através de pesquisa quasi-experimental com aplicação de pré-teste e pós-teste, utilizando grupos controle não equivalentes. Textos refutacionais de pesquisas já publicadas foram utilizados nas intervenções, assim como testes de performance correspondentes aos textos. Os conceitos abordados foram energia e natureza particulada da matéria. Os estudos foram conduzidos em duas turmas de 9o ano de uma escola municipal no sul do Brasil. Análises estatísticas do desempenho nos testes mostraram melhora significativa dos estudantes que utilizaram o SOBEK como suporte para estudo dos textos. Investigações mais detalhadas são necessárias para identificar a ocorrência e extensão das modificações na estrutura conceitual dos estudantes e sua relação com a estratégia proposta.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 student´s 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