Mohammad Hasibul Hasan, Asma Akter, Mohammad Ilias, Shakila N Khan, M Mozammel Hoq* Department of Microbiology, University of Dhaka, Dhaka-1000, Bangladesh.
(Received 2 December 2010 ; Accepted 5 February 2011)
This study was aimed at the large scale production and application of Bacillus thuringiensis (Bt) biopesticide in Bangladesh agriculture from locally available cheap raw materials. B. thuringiensis subsp. kurstaki HD-73 (reference strain) and two other indigenous isolates of B. thuringiensis namely Bt-Soil-47 and Bt-Insect-1i demonstrated satisfactory growth of sporulation and endotoxin production in a medium prepared from de-fatted mustard-seed meal (oil cake) as carbon and nitrogen sources at 30°C. A correlation of growth, sporulation and endotoxin production pattern was obtained through the systematic study over the period of 72 h. Time course study of the growth of all three Bt isolates demonstrated similar pattern; however, spore-crystal complex formation of the indigenous Bt isolates was different with respect to the reference strain. The two indigenous isolates formed the maximum sporecrystal complex at 36 h, whereas the reference strain did the same at 66 h. Hence, the productivity of endotoxin formation of the indigenous isolates, 34.30 10-3 and 37.50 10-3 g/L/h respectively, were higher than that of the reference strain (21.37 10-3 g/L/h). Spore-crystal complex of the bacilli was recovered as dry powder which can be applied suitably in field to test their insecticidal activity. Molecular size of endotoxin of the isolates analyzed by SDS-PAGE resembled the typical sizes of the δ-endotoxin of Bacillus thuringiensis. Keywords: Bacillus thuringiensis, spore-crystal complex, δ-endotoxin.
as biopesticide in agriculture4. However, to the best of our knowledge, there is no report on broad based and target-oriented study on Bt mass production in Bangladesh. This study focused on the large scale production and application of Bt biopesticide in Bangladesh agriculture from locally available cheap raw
materials. The cost of raw materials for the production of Bt production is considerably higher. Depending on the plant
production capacity, such cost varies from 30 to 40% of the
total cost in the conventional Bt production process5. Therefore, the production of this insecticide in developing countries like Bangladesh is largely depended on the cost and the production media made from locally available sources including agroindustrial by-products. During the course of our study, efforts were made to use defatted mustard-seed meal (oil-cake), one
of the most common by-products of edible oil industry in
Bangladesh, as a raw material for the production of Bt toxin from the reference strain Bacillus thuringiensis subsp. kurstaki HD-73 and two local isolates of Bt. The growth pattern and
toxin production of these organisms in the medium formulated from oil-cake was investigated and the efficiency of toxin
production by the two local isolates was compared with the
reference strain to find out a more potential toxin producing strain.
The competition for crops between human and insects is as old as agriculture. The use of chemical substances to control pests was started in the mid-1800s. In past, certain inorganic and organic
organophosphates, carbamatespyrethroids and formamides were
used as insecticides. Because of the special properties of these chemicals, such as long residual action and toxicity to a wide spectrum of organisms, they have been being used for a long
time. However, using such chemicals may cause many
environmental problems; for example, insect resistance, toxicity to humans, and to beneficial insects1.
The control of pest populations by using insect pathogens has been an attractive alternative to the application of chemical pesticides2-3....