Purification and characterisation of a fungicidal peptide from Bacillus amyloliquefaciens NCPSJ7

Bacillus amyloliquefaciens NCPSJ7 could secrete extracellular antimicrobial substances, showing potent antifungal activities. An active peptide AFP3 was isolated from the fermentation supernatant. After chromatography, the purified peptide was tested for the fungicidal activity, molecular mass, and stability. The results indicated that the peptide with a molecular mass of around 3.3 kDa, showed discernible inhibition of the pathogen Fusarium oxysporum f. sp. niveum with the minimum fungicidal concentration of 31 µg/ml. It also exhibited excellent inhibition of some representative pathogenic fungi at a low concentration. Moreover, the peptide remained active at a wide range of temperatures and pH. Ion Na+ may even increase the antifungal activities. At the same time, the peptide could well tolerate the treatment with trypsin. Electron microscopy was used to investigate the effect of the peptide on the pathogens. The peptide inhibited the growth of pathogens by disrupting the integrity of the hyphal membranes, resulting in their lysis. The potent fungicidal activities and stability made the peptide be a candidate for a biopreservative.