The present invention relates to a co-culture comprising Bacillus mycoides and Pythium aphanidermatum, and a method using the co-culture to produce bio-surfactants. The present invention also provides a biopesticide comprising the co-culture of Bacillus mycoides and Pythium aphanidermatum.本發明係關於一種包含蕈狀芽孢桿菌(Bacillus mycoides)與腐黴菌(Pythium aphanidermatum)之共培養物,及利用其生產生物界面活性劑之方法。本發明亦關於該共培養物用於製備防治植物病害之生物製劑的用途。