ABSTRACT
Aedes aegypti is the vector of Dengue disease, responsible for 20,000 deaths/year worldwide. Bacillus thuringiensis var israelensis - Bti releases selective and effective toxins (crystal proteins) against A. aegypti larvae. We present a low cost bioprocess for toxin production, accomplished by a selected Brazilian strain Bti (BR-LPB01) and employment of low cost substrates. Soybean meal and sugarcane molasses lead to high toxic effectiveness after 2L bioreactor fermentation (LD50=26ng/mL), near to the reference strain IPS82 (LD50=17.3 ng/mL). The pH ranged between 5.8 and 7.0 during the exponential growth period and between 7.0 and 8.4 during the stationary phase, with low activity. Thus, control of foam and pH 7.0 were started and proved to be crucial for high activity. It was verified that the fermentation could be discontinued after 20 hours, when the highest activity was present.
A dengue é transmitida pelo Aedes aegypti, doença responsável por 20.000 mortes/ano no mundo. Bacillus thuringiensis var israelensis libera toxinas seletivas e eficazes (proteínas cristal) contra larvas de A. aegypti. Propõe-se um bioprocesso de baixo custo para a produção da toxina, pelo emprego de uma cepa brasileira selecionada de Bti (BR-LPB01) e de substratos de baixo custo. Farelo de soja e melaço de cana levaram a eficácia tóxica alta após fermentação em biorreator 2L (DL50=26ng/mL), valor próximo a estirpe de referência IPS82 (DL50=17,3 ng/mL). O pH variou entre 5,8 e 7,0 durante o período de crescimento exponencial e entre 7,0 e 8,4 durante a fase estacionária, com baixa atividade larvicida. Assim, controles de espuma e de pH 7,0 foram iniciados e demonstraram serem cruciais para alta atividade. Verificou-se que a fermentação deve ser interrompida após vinte horas, quando se obtém a maior atividade.
ABSTRACT
The Perequê and Penedo rivers flow through the plains of Praia de Leste and fall into the sea between the municipalities of Pontal do Sul and Ponta do Poço. Both of these rivers belong to the sub-basin of Paranaguá Bay, and are constituent parts of the hydrographic basin of the Atlantic Ocean (State of Paraná). Four sites along the Perequê River (Stations 1-4) and one along the Penedo River(Station 5) were monitorated for water pollution over a 12 month period. During the period of December 1995 to November 1996, three water samples were collected from each site, placed in sterilized bottles and transported to the laboratory in ice-boxes. They were analyzed for the occurrence of total and decal coliforms, temperature and pH. Fecal pollution was detected throughout the period of study. Coliform contamination was smaller in Station 1 and 5 than in any other sites, probably due to lesser influence from urbanized areas. Water as Station 4 was strongly contaminated due to its close proximity to a sewage canal. This study demonstrated that the Pequerê and Penedo rivers, freshwater shrimps habitats, were heavily contaminated with fecal indicator bacteria, and this occurrence was not related with temperature or pH(au)