Efeito do pH e do ácido acético sobre a produção de bioinseticida por Bacillus thuringiensis a partir de glicerol proveniente da fabricação de biodiesel [thesis]

Marta Heloisa dos Reis Chagas
AGRADECIMENTOS Como já dizia Fernando Antinelli: "Sonho parece verdade quando a gente esquece de acordar (...)". Hoje vivo a realidade que parece um sonho, o qual requereu muito esforço, determinação, paciência e perseverança para que se pudesse concretizar. Sonho esse que não teria conseguido se estivesse sozinha. Por esse motivo deixo expressa aqui a minha eterna gratidão a todos aqueles que me acompanharam nessa jornada, de maneira direta ou indireta. Agradeço ao meu eterno amigo e
more » ... o amigo e orientador, Prof. Dr. Arnaldo Márcio Ramalho Prata, às suas preciosas críticas e sugestões e por ter compartilhado comigo parte dos seus conhecimentos. À minha família, especialmente minha mãe Vilma H. P. R. Chagas, por todas as orações em meu favor, toda preocupação, todo carinho e cuidado. À irmã que a vida me deu, Adriana A. Rossi, pelo companheirismo, pela cumplicidade, pela amizade de todos esses anos e por estar presente mesmo que à distância. Agradeço às minhas queridas alunas de iniciação científica Júlia Fernandes e Thaís Rodrigues, pela mão que sempre se estendia quando eu precisava, pelo apoio, pelo incentivo e pela grande amizade que se construiu. Obrigada à minha afilhada Ana Beatriz e aos amigos Thiago Vieira, Guilherme Lopes e Wagner Freitas. Enfim, obrigada a todos pela paciência, pelo sorriso, pelo abraço. Essa caminhada não teria sido a mesma sem vocês. Palavras-chave: Bioinseticidas. Glicerol. Ácido acético. Bacillus thuringiensis. Biodiesel ABSTRACT CHAGAS, M. H. R. Effect of pH and acetic acid on bioinsetice production by Bacillus thuringiensis using glycerol from biodiesel synthesis. 2012. 74 p. Dissertation (Master Bacillus thuringiensis is a gram-positive soil bacterium that is distinguished by the ability of synthesizing a protein crystal adjacent to the spore. This protein is responsible for the toxic action against several species of Diptera, as the larvae of the Aedes aegypti mosquito, which is the main vector of dengue. As Brazil possesses temperature and socioeconomic conditions that favors proliferation of the dengue transmitting mosquito, it is one of the major concerns to health agencies in Brazil. Brazil stands out for developing alternative fuel sources to petroleum fuels such as ethanol and biodiesel. However, during the transesterification reaction of oils/fats for the production of biodiesel glycerin is also generated. As there is no demand for this sub-product in the global market, its fate has become a problem and a challenge for the biodiesel industry. Therefore the development of an insecticide for fighting dengue using glycerol as the carbon source is a way to find new applications for glycerin and to contribute to the control of a disease with nationwide impact, considered a public health problem. Studies have shown that acetic acid is a compound produced and consumed by Bacillus thuringiensis' cells during their growth. Moreover, it presents a major role in the production of a compound called poly-βhydroxybutyrate (PHB), which is critical for providing energy for the toxin synthesis. In the present study, it was studied the effect of acetic acid on the growth of Bacillus thuringiensis and on the larvicidal activity of the fermented broth on the larvae of Aedes aegypti. The concentrations tested were 1 g/L, 3 g/L and 5 g/L of acetic acid, added in the following stages: (i) beginning of the fermentation, (ii) time of minimum pH value and (iii) time of deceleration of the increasing pH value. The assays were performed in 1000 mL Erlenmeyer flasks in a reciprocating motion shaker. The results showed that the addition of acetic acid at the beginning and at 10 hours of fermentation improves cell growth and toxin production. The most significant result regarding toxin production was achieved with the addition of 5 g/L of acid at the beginning of the fermentation. In this assay the net percentage of killing of the larvae was eight times higher than the results found in the test without the addition of acid (control test). For the test in which acetic acid was added at 20 hours of fermentation it was observed a higher cellular concentration, however, there was a lower larvicidal activity of the fermented broth, compared to the control test.
doi:10.11606/d.97.2012.tde-28082013-103230 fatcat:e6kk5jyg6vafdhln4ux6vwfzxy