Utilization of silkworm litter and pupal waste-an eco-friendly approach for mass production of Bacillus thuringiensis

The objective of the present study was to investigate the utilization of pupal waste and silkworm litter separately as production media for the mass cultivation of the potential biopesticide, Bacillus thuringiensis (Bt). Bt is the most successful commercial biopesticide accounting for 90% of all biopesticides sold all over the world. Biochemical analysis of the dry pupal waste revealed to be consisting of 4% carbohydrates, 44.9% proteins and 40% lipids. Similarly the biochemical composition of dry silkworm litter was found to be 4% carbohydrates, 57.5% proteins and 30.5% lipids. B. thuringiensis NCIM No. 2159 was mass cultivated in a semi-solid-state fermentation at a pH 7.0 and temperature 32 °C. Changes in the pH and biochemical composition of the substrates were evaluated during the course of the fermentation. The reliability of the two substrates as production media was evaluated by determination of growth at regular intervals. Maximum growth was recorded at 96 h incubation showing a spore count in the order of 3.5 × 1010 and 3.0 × 1010 CFU/g in pupal waste and silkworm litter respectively.