Production of Bacillus thuringiensis‐based biopesticides in batch and fed batch cultures using wastewater sludge as a raw material

Bacillus thuringiensis subsp kurstaki was grown in batch and fed batch cultures using wastewater sludge as a raw material. A simple fed batch strategy based on dissolved oxygen measurement during the fermentation cycle was developed in this work. It was established that while shifting the process strategy from batch to fed batch, the maximum spore concentration was increased from 5.62 × 108 to 8.6 × 108 colony forming units per cm3 and resulted in an increase of entomocidal activity from 13 × 109 to 18 × 109 spruce budworm potency units per dm3. Higher entomotoxicity was recorded at low spore concentration using wastewater sludge as a raw material whereas low entomotoxicity was reported at high spore concentration in synthetic medium.