Effect of temperature, pH and substrate composition on production of lipopeptides by Bacillus amyloliquefaciens 629

The lipopeptides surfactin, fengycin and iturin produced by Bacillus species have diverse ecological roles, including antimicrobial activity, induced systemic resistance in plants against pathogens and plant colonization by the producing strain. The conditions that govern both lipopeptide production and plant colonization are not fully understood. The present study investigated the role of growth media, temperature and pH on the production of the lipopeptides surfactin, fengycin and iturin by Bacillus amyloliquefaciens 629 and its production in bean plants colonized epiphytically and endophytically by this isolate. Surfactin was produced at higher amounts when isolate 629 was grown at 15 than at 25 and 30oC, whereas fengycin remained approximately constant across different temperatures. Iturin was detected on bean stem sap, root exudates and in potato dextrose broth, indicating that plant-derived nutrients play an important role in its production by isolate 629. B. amyloliquefaciens 629 colonized plants with more efficacy at 28 than at 20°C. None of the lipopeptides was detected in plants colonized by isolate 629, despite the number of attempts performed with ultra-performance liquid chromatography (UPLC) analysis.   Key words: Bioaccumulation, fengycin, iturin, surfactin.