Desenvolvimento de um meio de cultura de baixo custo para Bacillus thuringiensis subsp. israelensis

Abstract

Bacillus thuringiensis is a Gram-positive spore-forming bacterium that produces a parasporal crystal toxic for many insects. The aim of this study was the development of a low-cost medium for the culture of B. thuringiensis subsp. israelensis HD 537 to be used in a local insect control program in Brazil. In this study, the evaluated parameters were bacterial growth and toxicity of the cultures against Aedes aegypti larvae. The first strategy analised was the effect of salts, glucose, and yeast hydrolizate concentrations in a modified Arcas medium. The maximum toxicity in the bioassays (LC50 2.31 mg.l-1) were obtained by using a medium showing the highest tested concentrations of nitrogen sources and salts (8.00 e 0.47 g.l-1, respectively). In the second strategy was used a medium based in a ground Bombyx mori pupae. The maximum toxicity (LC 50 3.64 mg.l-1) was obtained with Bm 100 medium, with 100 g.l-1 of ground B. mori pupae. Beyond of the significant media differences in LC50 values, Bm100 medium was 120 times less expensive than the best Arcas modified medium. Thus, these results confirm the viability of ground B. mori pupae for B. thuringiensis subsp. israelensis growth and crystal production.