Abstract
Bacillus thuringiensis var. kurstaki has been widely used in caterpillar control programs. Large-scale production of this bacterium is expensive because of the high cost of the raw materials used in the medium. In this study, we attempted to develop an economical medium, based on inexpensive, locally available raw materials using a 3-L fermenter. Parthenium hysterophorus L. extract based culture medium resulted in highest toxicity (LC
50
14.628 µg mL-
1
) against 7-day-old Spodoptera litura (Fab) larvae, spore count (4.1 × 10
9
spores mL
-1
) and biomass (4.9 g L
-1
) within a short fermentation time of 36 h. It was 512 times cheaper than the nutrient broth (standard medium) used for B. thuringiensis production. Hence, this parthenium extract based culture medium was considered most economical with potential for the large-scale industrial production of B. thuringiensis.