Obtenção de bioinseticida a partir de Bacillus thuringiensis var. israelensis e aplicação de bioensaios em culicídeos
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Data
2004-06-14
Autores
Ernandes, Samara [UNESP]
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
A bactéria Bacillus thuringiensis var. israelensis (Bti) gera certas toxinas com ação inseticida que podem ser usadas no controle de doenças transmissíveis através de culicídeos, especialmente o Aedes aegypti, vetor da dengue. Este bioinseticida tem sido produzido através de fermentação submersa e, no Brasil, esta produção tem sido realizada através de pequenos centros de investigação e, mais recentemente, por uma pequena empresa. Para a implementação de um programa de controle de vetores viável através de bioinseticidas, alguns estudos sobre meio de cultura são essenciais para unir eficiência e baixos custos. Assim, tem-se utilizado resíduos ou subprodutos agroindustriais como fontes de nutrientes em meio de cultura. Neste estudo, alguns resíduos e subprodutos tais como água de maceração de milho (“milhocina”), um subproduto do processamento industrial do milho, “manipueira”, um subproduto do processamento da farinha de mandioca e sangue bovino oriundo de abatedouros foram avaliados com o intuito de se verificar a eficiência em processo fermentativo para obtenção de bioinseticidas. O crescimento celular foi avaliado por densidade óptica a 620 nm, a produção de esporo por plaqueamento em ágar nutriente e a CL 50 (Concentração letal média), por bioensaios contra larvas de 4º instar de Ae. aegypti. Foi verificado, em estudos com “manipueira”, que quando este subproduto é utilizado em baixa concentração, há o mesmo ou um melhor efeito do que quando se utiliza em concentração alta. A esterilização parece ser necessária ao processo fermentativo, pois quando se comparam ambos os meios de “manipueira”, um submetido à esterilização e outro sem este processo, o primeiro produziu mais esporos e uma melhor eficiência em bioensaios. Da mesma forma, quando o sangue de bovinos é acrescentado ao meio de “manipueira”, há um aumento...
The bacterium Bacillus thuringiensis var. israelensis (Bti) generates certain toxins with pesticid action, which can be used on the control of transmissible diseases by culicides, specially Aedes aegypti, the dengue´s vector. This biopesticide has been produced by submerged fermentation and, in Brazil, this production has been made by very little research centers and, more recently, by a unique small enterprise. For the implementation of a viable vectors control program through bioinsecticides, some studies about culture media are essential in order to join efficiency and low costs. So, agroindustrial wastes or by-products have been utilized as nutrient source for the culture media production. In this study, some wastes and by-products like corn steep liquor (“milhocina”), a corn industrial processing byproduct, “manipueira”, a by-product from cassava flour processing and cattle blood proceeding from slaughterhouses were utilized as substrate in order to verify the efficiency on fermentative process to obtain bioinsecticides. Cellular growth was evaluated by optical density at 620 nm, spore production by pour plate count and LC50 by bioassays against 4th instar larvae. It was verified, in studies with “manipueira”, that a low concentration of this byproduct has the same or better effect compared with high concentrations. The sterilization was a requisite to the fermentative process because when compared both sterilized and no sterilized “manipueira” media, the first yielded more spores and better efficiency in bioassays. Likewise, when cattle blood is added to “manipueira” media, there is an increase on the spores number and effectiveness against Ae. aegypti larvae. It was compared a traditional nitrogen source, peptone, with “manipueira”, with and without salts and glucose, tested separately and joined. In both media, salts had an importance, but the glucose didn´t seem necessary.
The bacterium Bacillus thuringiensis var. israelensis (Bti) generates certain toxins with pesticid action, which can be used on the control of transmissible diseases by culicides, specially Aedes aegypti, the dengue´s vector. This biopesticide has been produced by submerged fermentation and, in Brazil, this production has been made by very little research centers and, more recently, by a unique small enterprise. For the implementation of a viable vectors control program through bioinsecticides, some studies about culture media are essential in order to join efficiency and low costs. So, agroindustrial wastes or by-products have been utilized as nutrient source for the culture media production. In this study, some wastes and by-products like corn steep liquor (“milhocina”), a corn industrial processing byproduct, “manipueira”, a by-product from cassava flour processing and cattle blood proceeding from slaughterhouses were utilized as substrate in order to verify the efficiency on fermentative process to obtain bioinsecticides. Cellular growth was evaluated by optical density at 620 nm, spore production by pour plate count and LC50 by bioassays against 4th instar larvae. It was verified, in studies with “manipueira”, that a low concentration of this byproduct has the same or better effect compared with high concentrations. The sterilization was a requisite to the fermentative process because when compared both sterilized and no sterilized “manipueira” media, the first yielded more spores and better efficiency in bioassays. Likewise, when cattle blood is added to “manipueira” media, there is an increase on the spores number and effectiveness against Ae. aegypti larvae. It was compared a traditional nitrogen source, peptone, with “manipueira”, with and without salts and glucose, tested separately and joined. In both media, salts had an importance, but the glucose didn´t seem necessary.
Descrição
Palavras-chave
Bacillus thuringiensis, Resíduos - Agroindústria, Biotecnologia, Bioinsecticides, Agroindustrial wastes, Bacillus thuringiensis
Como citar
ERNANDES, Samara. Obtenção de bioinseticida a partir de Bacillus thuringiensis var. israelensis e aplicação de bioensaios em culicídeos. 2004. 124 f. Tese (doutorado) - Universidade Estadual Paulista, Instituto de Química de Araraquara, 2004.