Bioconversion of industrial wastewater and wastewater sludge into Bacillus thuringiensis based biopesticides in pilot fermentor

Starch industry wastewater (SWW), slaughterhouse wastewater (SHWW) and secondary sludges from three different wastewater treatment plants (Jonquière—JQS, Communauté Urbaine de Québec—CUQS and Black lake—BLS) were used as raw materials for the production of Bacillus thuringiensis (Bt) based biopesticides in a pilot scale fermentor (100 L working volume). The slaughterhouse wastewater exhibited the lowest Bt growth and entomotoxcity (Tx) potential (measured against spruce budworm) due to low availability of carbon, nitrogen and other nutrients. Performance variation (growth, sporulation, proteolytic activity and Tx potential) within the three types of sludges was directly related to the availability of nitrogen and carbohydrates, which could change with sludge origin and methods employed for its generation. The Tx potential of Bt obtained in different secondary sludges (JQS: 12 × 109 SBU/L; CUQS: 13 × 109 SBU/L and BLS: 16 × 109 SBU/L) and SWW (18 × 109 SBU/L) was higher than the soybean based synthetic medium (10 × 109 SBU/L). The maximum protease activity was obtained in CUQ secondary sludge (4.1 IU/mL) due to its high complex protein concentration. Nevertheless, high carbohydrate concentration in SWW repressed enzyme production. The secondary sludges and SWW were found to be suitable raw materials for high potency Bt biopesticide production.