Characterization and Synergistic Antimicrobial Evaluation of Lipopeptides from Bacillus amyloliquefaciens Isolated from Oil-Contaminated Soil

Abstract

Lipopeptides show great potential for biomedical application. Several lipopeptides exhibit narrow and broad-spectrum inhibition activities. The aim of the study is to characterize the lipopeptides produced by B. amyloliquefaciens strain MD4-12 and evaluate the synergistic antimicrobial activity in combination with a conventional antibiotic against Gram-negative bacteria. B. amyloliquefaciens strain MD4-12 was isolated from oil-contaminated soil. The isolate was cultivated in McKeen medium, and the lipopeptides were isolated by precipitation and extraction with methanol. Characterization of the lipopeptides by ESI-MS gave nine mass ion peaks with m/z 994–1072, resulted from protonating of the main ions in [M + H]+ and [M + Na]+ ion form. These mass ion peaks attributed to surfactin homologs. By tandem mass spectrometry, five variants of surfactin with the same amino acid sequence in peptide moiety could be revealed. The peptide moiety contains seven amino acids identified as Glu-Leu/Ile-Leu-Val-Asp-Leu-Leu/Ile while the fatty acid moiety comprises a different length of chain from C12 to C16. Surfactin showed antibacterial activity against various Gram-positive and Gram-negative bacteria. Combination surfactin with ampicillin showed a synergistic effect against P. aeruginosa ATCC 27853.

The use of low-cost brewery waste product for the production of surfactin as a natural microbial biocide

“…The MIC was determined by resazurin assay in a 96 well-plate for P. aeruginosa (MIC 1024 g m ). The different surfactin isoforms could be a reason for the higher MIC compare to this work since Sudarmono et al [44] reported the presence of several isoforms of surfactin ( – ), mainly surfactin and .…”

“…Sudarmono et al [44] reported that surfactin produced by B. amyloliquefaciens presented antimicrobial activity against S. aureus ATCC 25923, P. aeruginosa ATCC 27853 and E. coli ATCC 25922, showing Inhibition zone diameter of 20.0, 15.7 and 11.4 mm, respectively. The MIC was determined by resazurin assay in a 96 well-plate for P. aeruginosa (MIC 1024 g m ).…”

“…The variation in the structural composition of surfactin can be the main reason for antimicrobial activity, since it can significantly influence the physico-chemical properties and physiological activities, including interaction with the microbial membrane. The composition of surfactin is highly dependent on strain, culture condition, and growth medium composition [35] , [44] .…”

Selection of sponge-associated bacteria with high potential for the production of antibacterial compounds

“…Surfactins are cyclic lipopeptides with surfactant-like properties, interfering with many kinds of cell membranes. They were reported to show antibacterial activity in agar diffusion assays against various test strains if used at high concentrations 55,56 . However, these results must be interpreted with caution, since the MICs determined were > 1024 µg/mL 56 , indicating no activity.…”

“…They were reported to show antibacterial activity in agar diffusion assays against various test strains if used at high concentrations 55,56 . However, these results must be interpreted with caution, since the MICs determined were > 1024 µg/mL 56 , indicating no activity. The debate on the antimicrobial effect of surfactins remains active, but may be accounted to the non-specific mode of action on the cell layer, e.g.…”