Utilisation of response surface methodology to optimise the culture medium for Bacillus thuringiensis subsp. israelensis |
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Authors: | Elisangela Andrade Angelo Gislayne Trindade Vilas-Bôas Raúl Jorge Hernan Castro-Gómez José Lopes |
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Affiliation: | 1. Departamento de Ciências e Tecnologia de Alimentos, Universidade Estadual de Londrina, Londrina, Brazil;2. Departamento de Biologia Geral, Universidade Estadual de Londrina, Londrina, Brazil;3. Departamento de Biologia Animal e Vegetal, Universidade Estadual de Londrina, Londrina, Brazil |
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Abstract: | Bacillus thuringiensis israelensis (Bti) is a sporulating Gram-positive bacterium that produces protein crystals with insecticide activity against Diptera. The aim of the present work was to optimise the culture medium for this bacterium, based on mathematical and statistical concepts (factorial designs and response surface methodology). The variables studied were carbon and nitrogen source concentrations. The main response analysed was toxicity, evaluated by means of bioassay with Aedes aegypti. The nutrient sources were first selected and then optimised. Ground Bombyx mori pupae, ammonium sulphate and glucose were the most suitable sources of organic nitrogen, inorganic nitrogen and organic carbon, respectively. The toxicity of optimised medium (LC50 = 0.703 ppm, v/v) was higher than that the medium used as reference (LC50 = 3.01 ppm, v/v), which is commonly used in the laboratory culture of Bti. Besides, the optimised medium showed a cost 7.36 times less than that of an alternative medium, based on soybean flour and sugarcane molasses. Factorial design and response surface methodology were effective methods for culture medium optimisation. The results will contribute to the development of local production and utilisation of agroindustrial waste locally. |
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Keywords: | Bacillus thuringiensis factorial design response surface methodology biological control Aedes aegypti |
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