Structural characterization of lipopeptides from Enterobacter sp. strain N18 reveals production of surfactin homologues

Abstract

Lipopeptides are amphiphilic biosurfactants which contain fatty acid chains and peptide chains. A novel lipopeptide producer was isolated from soil samples and identified as Enterobacter sp. by using 16S rRNA gene sequencing. The surface tension of the cell-free broth decreased from 58.0 mN/m to 27.9 mN/m after the strain was incubated for 48 h at 37°C. The fatty acid part of the lipopeptide was elucidated by ESI-MS and GC-MS after methyl esterification, which showed that fatty acids were mixtures of n-C 12 , iso-C 13 , anteiso-C 13 , iso-C 14 , n-C 14 , iso-C 15 , anteiso-C 15 , iso-C 16, n-C 16 and iso-C 17 b-hydroxy fatty acids. The peptide sequence, of which the composition of amino acids was determined by GC-MS with trimethylsilylation, was deduced to be N-Glu-Leu-Leu-Val-Asp-Leu-Leu-C by using Q-TOF MS/MS. The fatty acid chain was bonded to the N-terminal of the peptide moiety, and a cyclic ring was constituted by the hydroxyl group of the fatty acid chain and the C-terminal.Practical applications: The systematic characterization methods used in this article are helpful for structural analysis of those lipopeptide-like compounds. The information of Enterobacter-produced surfactin helps us to enlarge the family of surfactin-producers and expand the recognition of metabolites of Enterobacter spp.

Isolation and characterization of kurstakin and surfactin isoforms produced by Enterobacter cloacae C3 strain

“…strains, respectively. Also, according to You et al the fragmentation of the parent ion at m/z 1058.6 was recognized to be sodium adducts of C 15 surfactin. Plaza et al reported that the sodiated molecules [M + Na] + m/z 1044, 1058, and 1072 correspond to C 14 , C 15 , and C 16 surfactin homologues, respectively, obtained from lipopeptides produced by Bacillus subtilis KP7 strain.…”

“…This is the first work describing kurstakin, surfactin, and pumilacidin lipopeptide mixture production from E cloacae strain. In fact, the study of You et al describes the production of surfactin homologues from Enterobacter sp. N18 strain.…”

“…Biosurfactants are synthesized by a wide variety of microorganisms, mainly by bacteria and several yeasts . Lipopeptides are among the most studied bioactive molecules, produced by multiple bacterial genera such as Bacillus , Paenibacillus , Pontibacter , Achromobacter , Corynebacterium , Pseudomonas , Streptomyces , Citrobacter , and Enterobacter …”

“…Cyclic lipopeptide biosurfactants like surfactin, iturin, bacillomycin, fengycin, and kurstakin are largely produced by species of the genus Bacillus , which are Gram‐positive bacteria exhibiting antimicrobial activity . There are few studies describing the production of these lipopeptide families by Gram‐negative bacteria . Usually, Gram‐negative bacteria of the genera Pseudomonas , Klebsiella , and Enterobacter produce rhamnolipid and glycolipid biosurfactants …”

“…15,16 There are few studies describing the production of these lipopeptide families by Gramnegative bacteria. 9,10 Usually, Gram-negative bacteria of the genera Pseudomonas, Klebsiella, and Enterobacter produce rhamnolipid and glycolipid biosurfactants. [17][18][19][20] Different analytical techniques for chemical characterization of lipopeptides have been applied to elucidate their structure such as infrared spectroscopy (IR), amino acid analysis, high-performance liquid chromatography (HPLC), capillary chromatography coupled to mass spectrometry (MS), gas chromatography (GC-MS), and UV/vis spectroscopy, 21 nuclear magnetic resonance (NMR) spectroscopy, and liquid chromatography-mass spectrometry (LC-MS).…”