Abstract: A highly toxic Bacillus thuringiensis strain NBIC-380 against Asian corn borer was treated by atmospheric and room temperature plasma for improving the toxicity of the resulting mutants. Through 4 rounds of ARTP mutation and screening by microscopic checking,shake-flask fermentation and bioassay,one mutant designated as Bt-NBIC-380-18-407 with significant improvement of production of insecticidal crystal protein and potency-was obtained. The potency of the fermentation broth of the mutant against Asian corn borer larvae was increased 25.7% to 6 835 IU/μl,while the concentration of insecticidal crystal protein in fermentation broth was increased 18.9% to 6.3 mg/mL. The mutant showed rather good genetic stability after 5 times of consecutive transferring and cultivation.

Key words: ARTP mutagenesis, Bacillus thuringiensis, Asian corn borer, insecticidal crystal proteins, potency