Iturin and surfactin from the endophyte Bacillus amyloliquefaciens strain RKEA3 exhibits antagonism against Staphylococcus aureus

Bacillus amyloliquefaciens strain RKEA3, an isolated endophytic strain from Avicennia officinalis, was found to be shown antagonistic activity against Staphylococcus aureus ATCC25923, Streptococcus pyogens ATCC19615, Staphylococcus aureus ATCC 9219, clinical strains of Staphylococcus aureus and Cryptococcus neoformans. The antimicrobial lipopeptide produced by this strain was isolated by acid precipitation followed by dialysis, lyophilization, and methanol extraction. The influence of various parameters on the antibacterial activity of isolated lipopeptide was studied, and it was found that they could survive a wide temperature and pH range. Proteolytic enzymes, metals, surfactants, and organic solvents had no effect on its action. A typical lipopeptide absorption peak and a band of peptide bonds and ester groups were visible in the UV and FTIR spectra of the isolated lipopeptide. The Rf values of bioactive lipopeptide on developed TLC plate against Staphylococcus aureus ATCC25923 were calculated as 0.82 and 0.75 by bioautographic assay. The existence of ituD, ituD1, sfp, and sur3 genes in the genome and mass spectra of isolated lipopeptide revealed that Bacillus amyloliquefaciens strain RKEA3 could produce an array of iturin and surfactin-like peptides. The antibacterial effectiveness of isolated lipopeptide against several bacterial strains and its substantially lower hemolytic activity suggest that it could be developed as a medicine.