Abstract
Surfactins are lipopeptide-type biosurfactants produced mainly by Bacillus species, consisting of a peptide loop of seven amino acids and a hydrophobic fatty acid chain (C12–C16). These molecules have been proven to exhibit various biological activities; thus, their therapeutic and environmental applications are considered. Within the surfactin lipopeptide family, there is a wide spectrum of different homologues and isomers; to date, more than 30 variants have been described. Since the newest members of these lipopeptides were described recently, there is no information that is available on their characteristic features, e.g., the dependence of their production from different cultivation parameters. This study examined the effects of both the different carbon sources and various metal ions on the surfactin production of a selected B. subtilis strain. Among the applied carbon sources, fructose and xylose had the highest impacts on the ratio of the different variants, regarding both the peptide sequences and the lengths of the fatty acids. Furthermore, the application of metal ions Mn2+, Cu2+ and Ni2+ in the media completely changed the surfactin variant compositions of the fermenting broths leading to the appearance of methyl esterified surfactin forms, and resulted in the appearance of novel surfactin variants with fatty acid chains containing no more than 11 carbon atoms.
Highlights
Surfactins are biosurfactants belonging to the family of cyclic lipopeptides, which were first described in 1968 [1], and are mainly produced by gram-positive Bacillus species includingB. amyloliquefaciens, B. licheniformis, B. mojavensis, B. pumilus, and B. subtilis [2,3,4,5,6]
Modified culture media were applied to examine the effect of various carbon sources on the surfactin production of B. subtilis Szeged Microbiology (SZMC) 6179J, and on the qualitative and relative quantitative compositions of the different variants
It is important to consider that the mentioned modifications may have different effects on other B. subtilis strains, possibly promoting the forming of other surfactin profiles, and even the production of other novel variants
Summary
B. amyloliquefaciens, B. licheniformis, B. mojavensis, B. pumilus, and B. subtilis [2,3,4,5,6] These molecules were isolated in the form of needle-shaped white crystals, and denominated according to their outstanding surface activities. These compounds exhibit a wide range of different biological activities, such as anti-mycoplasmic [7], anti-viral [8], anti-tumor [9], and anti-inflammatory activities [10]. Due to their surface effect, the application of surfactins in environmental research is gaining growing interest [11]. Surfactins consist of a hydrophobic β-hydroxy fatty acid ‘tail’ part and a ‘head’ part of seven amino acids connected by a lactone bridge, which forms the cyclic structure of the molecules [12].
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