Uso do peróxido de hidrogênio no controle de cianobactérias - uma perspectiva bioquímica / Use of hydrogen peroxide in the control of cyanobacteria - a biochemical perspective

RESUMO As florações de cianobactérias vêm aumentando em intensidade e frequência em todo o mundo, ameaçando a sustentabilidade dos recursos aquáticos e o abastecimento humano. A construção de reservatórios, o uso de fertilizantes artificiais e o descarte de esgotos não tratados são os principais motores dessa expansão. As alterações climáticas, como o aquecimento global, as chuvas e as secas extremas, têm contribuído para a acelerar esse processo. Qualquer medida de mitigação dessas florações deve considerar os impactos sobre os outros organismos, os custos, além dos resíduos gerados. Nessa perspectiva, a aplicação do peróxido de hidrogênio em reservatórios artificiais traz uma série de vantagens para o controle a curto prazo, sendo uma das principais a destruição seletiva de cianobactérias. Apesar de vários estudos indicarem que as cianobactérias são o alvo preferencial do peróxido de hidrogênio, uma explicação bioquímica desse fenômeno ainda não foi encontrada. Este trabalho, portanto, procura congregar assuntos relacionados a esse tema e traz também uma coletânea de experiências recentes sobre o uso em escala real do peróxido de hidrogênio, apontando as principais lacunas de conhecimento que deverão ser preenchidas caso sua utilização em reservatórios seja para abastecimento. Uma das lacunas a ser preenchida está relacionada às vantagens do peróxido de hidrogênio sobre outros métodos de controle, pois apresentam maior eficiência no controle de cianobactérias posto que são preferencialmente destruídos pelo peróxido de hidrogênio, em relação aos fitoplânctons, sendo, dessa forma, importante o estudo de técnicas de aplicação do peróxido de hidrogênio em reservatórios de grande porte.

ABSTRACT Cyanobacterial blooms are increasing in intensity and frequency throughout the world, threatening the sustainability of aquatic resources and human supplies. The construction of reservoirs, the use of artificial fertilizers and the disposal of untreated sewage are the main engines of this expansion. Climate change, such as global warming, rainfall and extreme droughts, has contributed to accelerate this process. Any mitigation measure of the blooms should consider the impacts on the other organisms, the costs beyond the waste generated. In this perspective, the application of hydrogen peroxide in the artificial reservoirs has a number of advantages for short-term control, one of the main ones being the selective destruction of cyanobacteria. Although several studies indicate that cyanobacteria are the preferred target of hydrogen peroxide, a biochemical explanation for this phenomenon has not yet been found. This work, therefore, seeks to gather subjects related to this topic and brings a collection of recent experiences on the real scale use of hydrogen peroxide, pointing out the main knowledge gaps that should be filled if their use in reservoirs is for supply. One of the gaps to be filled is related to the advantages of hydrogen peroxide over other control methods, as they present greater efficiency in the control of cyanobacteria, as they are preferentially destroyed by hydrogen peroxide in relation to phytoplankton, therefore, it is important to study the application techniques of hydrogen peroxide in large reservoirs.

Solid coffee waste as alternative to produce carotenoids with antioxidant and antimicrobial activities.

Special coffee production involves particular sensorial characteristics of the beverage as well as the production system of coffee beans, in particular environmental issues like water and solid waste disposal. Many countries around the world have problems with that waste disposal. The possibility to integrate the commodite production with suitable agricultural practices was the focus on this work using the solid waste to produce pigments by yeasts with biological activities. The better carotenoids production was tested previously in husk and pulp extract. The production of total carotenoids by yeast was 16.36 ±â€¯0073 mg L-1 was 21.35 ±â€¯0067 mg L-1, in the pulp extract and husk extract respectively. Carotenoids produced, exhibited antioxidant and antimicrobial activities against pathogenic bacteria such as Salmonella colorless, Escherichia coli, Staphylococcus aureus and Listeria monocytogenes as well as toxigenic fungi like Aspergillus flavus, A. parasiticus, A. carbonarius and A. ochraceus. These characteristics of the pigments are important to replace the artificial ones commonly used in food and pharmaceutical industries allowing the consumers to choose more natural products at lower costs.