Abstract: Bacillus amyloliquefaciens strain LJ1 isolated from the soil of Tianjin is biocontrol one with broad inhibition spectrum. This study aims to clarify the inhibition spectrum of strain B. amyloliquefaciens LJ1 and improve the antifungal activity by optimizing the medium composition and fermentation conditions. The confront culture was performed to test the antifungal activity of LJ1 on 14 phytopathogenic fungi. The medium composition and fermentation conditions were optimized by single-factor and orthogonal experiments. Finally, the inhibitory effect of optimized broth was tested by methods of spore germination and pot experiment. The results showed that B. amyloliquefaciens LJ1 inhibited 11 tested fungal pathogens, i. e. , Botrytis cinerea, Glomerella cingulata, and Valsa ceratosperma. The optimal fermentation conditions were as temperature 30℃, initial pH5.0, rotation speed 200 r/min, and medium volume 50 mL/250 mL. The optimal composition of the medium was 200 g potato, 10 g sucrose, 20 g soybean flour, 1.5 g MgCl₂·6H₂O, and 1 000 mL distilled water. In conclusion, the inhibition rate of B. amyloliquefaciens LJ1 to the conidia germination of B. cinerea reached 99.7%, and the control efficacy of pot experiment was 51.08% under the optimum fermentation medium and culture conditions.

Key words: Bacillus amyloliquefaciens LJ1, inhibition spectrum, optimization of fermentation condition