Antifungal activity of lipopeptides from Bacillus amyloliquefaciens MG3 against Colletotrichum gloeosporioides in loquat fruits

This work aims to produce and purify antifungal lipopeptides from fermentation by B. amyloliquefaciens MG3, and verify antifungal mechanism on C. gloeosporioides. Using Quadrupole-Time of Flight Mass Spectrometry (Q-TOF-MS) analysis, the component with antifungal activity in the fermentation supernatant of the MG3 strain was determined to be the lipopeptide antibiotic iturin A (C-14-C-15). Antagonistic tests showed that iturin A could inhibit the mycelia growth and spore germination of C. gloeosporioides. The minimal inhibitory concentration (MIC), half maximal inhibitory concentration (IC50) and minimal fungicidal concentration (MFC) of iturin A against C. gloeosporioides were 36.47, 74.95 and 110 mu g/mL, respectively. Iturin A induced an increase of cell membrane permeability and MDA content and a decrease of protein content in the fungal cell. It was observed that iturin A treatment resulted in smaller C. gloeosporioides lesion diameters on loquat fruit compared with the control group. Overall, the results of this study show that iturin A from B. amyloliquefaciens MG3 may be a potential biological control agent for postharvest preservation of loquat fruit.