Bioinsecticide production by the bacterium<i>Bacillus thuringiensis</i>. 1. Pattern 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 lower toxicity, when tested against Spodoptera littoralis and Anagasta kuehniella larvae. The best results were obtained with glucose concentration of 20.0 g 1−1 as 7.1 × 1011 spores ml−1 and 3.4 g l−1 of crystal protein were achieved with LC50 of 40.1 and 50.2 mg kg−1 meal against S. littoralis and A. kuehniella, respectively. However, >21% of the consumed glucose was 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 β-hydroxybutyric acid (PHB) were produced during the phase of active growth and glutamic acid and succinic acid during the phase of active toxin production.