Bioinsecticide production by the bacterium bacillus thuringiensis [patttern of cell growth, toxin production and by-product synthesis]

ABSTRACT

To develop a cost-effective process for the production of Bacillus thuringiensis based insecticide, it is important to cultivate the bacterial strain in rich medium to obtain the highest yields of spore-crystal complexes. It was found that cultivation of the bacterium in medium with high concentrations of glucose [50-90 g. l[-1]] resulted in much lower bacterial spores, crystal protein and their toxicity, when tested against Spodoptera littoralis and Anagasta kuehniella larvae. The best results was obtained with glucose concentration of 20.0 g.1[-1] as 7.1 x 10[11] spores/ml[-1] and 3.4 g/l of crystal protein were achieved with LC[50] of 40.1 and 50.2 mg/Kg mail against S. littoralis and A. kuehniella respectively. However, > 21% of the consumed glucose were diverted into by-product synthesis at the expense of spore-crystal protein mixture. Only 78.3% of consumed glucose was converted into spores and crystal protein. Among by-products formed, acetic acid and beta-hydroxybutyric acid [PHB] that were produced during the phase of active growth and glutamic acid and succinic acid during the phase of active toxin production