Abstract: Bacillus mojavensis strain D50 is a broad-spectrum biocontrol strain with antagonistic effects on many pathogenic fungi.Previous studies showed that the main antifungal substances produced by D50 were lipopeptide compounds.In this study,the stability of antifungal lipopeptide of strain D50 was determined by inhibitive clear zone method.It was found that the crude extract of lipopeptide had high stability in the environment of high temperature,non-extreme acid or alkaline condition and UV radiation.The medium for the production of antifungal lipopeptides from D50 was optimized by Plackett-Burman design and Box-Behnken response surface design methodology.The results showed that magnesium sulfate,glucose and yeast extract powder were the key factors to affect the lipopeptides yield.And the optimized medium compositions were determined as follows:glucose 15.45 g/L,beef extract 3.00 g/L,yeast extract powder 5.99 g/L,manganese sulfate 0.30 g/L,calcium chloride 0.30 g/L,ammonium sulfate 2.00 g/L,magnesium sulfate 0.16 g/L,potassium dihydrogen phosphate 1.50 g/L,and disodium hydrogen phosphate 2.00 g/L.By using this medium,the yield of lipopeptides reached 1.74 g/L with a higher proportion of 167.7% than that in the original medium.This study showed that the antifungal lipopeptide produced by strain D50 had high stability to environmental factors.The medium optimization provided valuable information for the large-scale production of antifungal lipopeptide by strain D50.

Key words: Bacillus mojavensis D50, antifungal lipopeptides, medium optimization, stability