Influência e custos de diferentes meios de cultura para produção de Bacillus thuringiensis visando o controle de pragas

Abstract

Bacillus thuringiensis (Bt) is a bacterium that has the ability to synthesize parasporal crystalline inclusions that shows toxic activity against a wide range of insects. B. thuringiensis can be used for pest control in the form of biopesticide. Biopesticide is a formulated product that can be sprayed in the field after the growth of Bt in culture medium. Some parameters should be followed for the production of effective and quality biopesticide product, the composition of the culture medium, and the physicochemical parameters (temperature, oxygen concentration, pH, rpm) are essentials. The purpose of this work was to evaluate the influence of the composition of the components of the culture medium on the Bt production - based biopesticide to control of agricultural pests. Four different media were used. Medium 1 (Luria Bertani- LB - check treatment): 1% tryptone, 0,5% yeast extract, 0,5% NaCl; Medium 2: 1,49% glucose, 0,92% yeast extract, 0,088% MgSO4; Medium 3: 1,49% glucose, 0,92% yeast extract, 0,09% MgSO4, 0,02% MnSO4, 0,03% CaCl2, 0,3% KH2PO4 and Medium 4: 1,49% glucose, 0,92% yeast extract, 0,09% MgSO4, 0,02% MnSO4, 0,03% CaCl2, 0,3% KH2PO4, 0,025% FeSO4, 0,023% (NH4) SO4, 0,28% K2HPO4, 0,008% ZnSO4. The Bt strain 1641 was used in this research. The bioassays were carried out using 1 day old larvae after hatching of Spodoptera frugiperda, S. cosmioides, S. eridania, Helicoverpa armigera, Anticarsia gemmatalis and Chrysodeixis includens. The pH was measured at regular intervals during the fermentation process, and showed variation among 4.60 and 8.75. The highest spore concentration was 8,92x108 spores/ml obtained in medium 3, after 48 hours of fermentation. Cell mass production was higher in medium 2 and accumulated 2.93 g/L. The efficiency of 100% mortality was obtained with the culture medium 1 for S. frugiperda, S. eridania, C. includens after 32 hours of fermentation and for A. gemmatalis, S. cosmioides and H. armigera after 08, 56 and 60 hours, respectively. Medium 1 was the most efficient medium for the production of B. thuringiensis as a biological pesticide.