Impact of different pH control agents on biopesticidal activity of Bacillus thuringiensis during the fermentation of starch industry wastewater

摘要

Different pH control agents (NaOH/H_2SO_4-SodSulp, NaOH/CH_3COOH-SodAcet, NH_4OH/CH_3CO-OH-AmmoAcet and NH_4OH/H_2SO_4-AmmoSulp) were used to investigate their effects on growth, enzyme production (alkaline protease and amylase), and entomo-toxicity of Bacillus thuringiensis var. kurstaki HD-1 (Btk) against eastern spruce budworm larvae (Choristoneura fumiferana) using starch industry wastewater (SIW) as a raw material in a 15-1 fermentor. AmmoSulp and SodSulp were found to be the best pH control agents for alkaline protease and amylase production, respectively; whereas, the fermented broth obtained by using SodAcel as pH control agents recorded the highest delta-endotoxin production of 1043.0 mg/1 and entomotoxicity value 18.4 × 10~9 SBU/1. Entomotoxicity of re-suspended centrifuged pellet in one-tenth of original volume in case of SodAcet as pH control agents was 26.7 × 10~9 SBU/1 and was the highest value compared to three other pH control agents.