The ultrasound-assisted extraction and identification of antifungal substances from B. amyloliquefaciens strain NJN-6 suppressing Fusarium oxysporum.

The primary mechanism underlying antagonism among microorganisms is the production of antagonistic substances called antibiotics that inhibit the growth of pathogens. In this study, the antagonistic substances produced by the Bacillus amyloliquefaciens strain NJN-6 that had antifungal activity against Fusarium oxysporum were extracted and identified. The active antifungal substance was extracted from dried leavening with ultrasound-assisted extraction (UAE), using n -butanol as the extractant. HPLC/ESI-MS was performed to investigate the components of the extracts. The results of the study showed that the antimicrobial substances consisted of three homologues of the iturin A family with molecular weights of 1043, 1057 and 1071 Da and of two homologues of the fengycin family with molecular weights of 1477 and 1491 Da. The effects of ultrasonic treatment time, extraction time and extractant volume, three major methodological parameters, were also studied to determine the optimal conditions for extraction. Compared with traditional extraction techniques, UAE is a simple, cheap and environmentally friendly method that represents a new option for the isolation and identification of lipopeptides and other active compounds. These antifungal substances extracted and identified from Bacillus amyloliquefaciens NJN-6 will help us to understand its biocontrol mechanism against Fusarium oxysporum.