Production of Bacillus thuringiensis var. kurstaki by three different methods and its relative toxicity to Bombyx mori

Abstract

The relative toxicity of Bacillus thuringiensis var. kurstaki produced by submerged culture, by surface culture using modified tryptone medium, and by in vivo culture using 3rd-instar silkmoth larvae, Bombyx mori, has been evaluated against mid-3rd-instar B. mori larvae. The submerged culture method was the most effective producing 272.5 × 10 3 toxicity units, followed by the surface culture and in vivo culture methods, producing 121.6 × 10 3 and 9.1 × 10 3 toxicity units per liter (of in vitro) and per kilogram (of in vivo) medium, respectively. Higher biomass and unfavorable growth conditions for B. thuringiensis (ku) resulted in production (5 × 10 9/g) of spore crystal complex by the in vivo culture method being the lowest; production from the submerged culture was intermediate (42 × 10 9/g); and production by the surface culture method was the highest (62 × 10 9/g). Products from the submerged and the surface cultures were 29.9 and 13.4 times more potent, respectively, than those from the in vivo culture method.