Characterisation of two novel bacteriocin-like substances produced by Bacillus amyloliquefaciens ELI149 with broad-spectrum antimicrobial activity.

OBJECTIVES

The aim of this study was to isolate and characterise antifungal and bactericidal compounds from Bacillus amyloliquefaciens strain ELI149.

METHODS

An absorbent resin (Amberlite® XAD-16) and silica gel column chromatography were used for isolation and purification purposes, respectively. Antibacterial and antifungal assays were performed by the well diffusion method to demonstrate the biological activity of each compound. Cell damage of the tested fungi was evaluated for fengycin under phase-contrast microscopy. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and mass spectroscopy techniques were performed to estimate the approximate molecular mass of each compound.

RESULTS

Two bacteriocin-like substances (BLSs) with different physical properties and inhibitory activities were isolated along with two known antifungal compounds. The two BLSs were heat stable and were not sensitive to acid or alkaline conditions (pH 2-10), with broad-spectrum antimicrobial activity. The antifungal compounds were identified as surfactin and fengycin. Only fengycin showed marked antifungal properties against several phytopathogens.

CONCLUSIONS

The two isolated BLSs were partially characterised and their bactericidal properties were analysed. The antifungals compounds were identified as surfactin and fengycin, this latter being mainly responsible for the antifungal activity.