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International Journal of Microbiology
Volume 2017 (2017), Article ID 5402748, 6 pages
https://doi.org/10.1155/2017/5402748
Research Article

Persistence of Toxic Activity of Fermentation Extracts from Bacillus thuringiensis var. israelensis after More Than Three Decades of Storage

1Instituto de Biotecnología, Facultad de Ciencias Biológicas, Universidad Autónoma de Nuevo León, Ciudad Universitaria, 66450 San Nicolás de los Garza, NL, Mexico
2Centro de Investigación/Facultad de Odontología, Universidad Autónoma de Nuevo León, Calle Dr. Eduardo Aguirre Pequeño y Silao s/n, Colonia Mitras Centro, 64460 Monterrey, NL, Mexico

Correspondence should be addressed to Luis Jesús Galán-Wong; moc.liamg@55wgjl

Received 4 August 2017; Revised 11 October 2017; Accepted 31 October 2017; Published 20 November 2017

Academic Editor: Giuseppe Comi

Copyright © 2017 Luis Jesús Galán-Wong et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

This study was carried out to determine the persistence of toxicity of fermentation extracts of Bacillus thuringiensis var. israelensis after more than three decades of storage. For this purpose, a population of Aedes aegypti was established. The mortality rate of 20 spore-crystal extracts purified using the acetone-lactose coprecipitation method was measured and evaluated by bioassays according to a modified WHO protocol. The extracts with the highest mortality rate were determined in triplicate by their LD50 and LD98. All extracts showed toxicity at the highest tested dose (1000 ppm) and some, such as strains 3260 and 3501, still killed larvae at doses as low as 0.01 ppm. These data are surprising because no study on the activity of B. thuringiensis toxic proteins after such a long storage time has been reported.