Growth of Four Serovar ofBacillus thuringiensis(Var.Kurstaki,Israelensis,Tenebrionis, andAizawai) in Wastewater Sludge

Abstract

Growth patterns of four different serovar of Bacillus thuringiensis (Bt) (Bt kurstaki, Bt israelensis, Bt tenebrionis, and Bt aizawai) were studied using wastewater sludge as a raw material. A comparative study using synthetic medium (soy) was also performed. It was observed that the four Bt strains gave cell counts of the order of 108 CFU∕mL in wastewater sludge and 109 CFU∕mL in synthetic medium. The sporulation (% spores) in two media was 90%. The entomotoxicity per unit spore (specific entomotoxicity) was much higher in sludge medium compared to synthetic medium. Therefore, sludge was a good source of nutrients for growth and toxin production by all types of serovar used in this study.