Effects of Different Cultivation Parameters on the Production of Surfactin Variants by a Bacillus subtilis Strain

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

Revealing of biodiversity and antimicrobial effects of Artemisia asiatica endophytes

Endophytic fungi produce a plethora of secondary metabolites, which may open new avenues to study their applicability in pharmaceuticals. Therefore, the present study focuses on the fungal endophytic community of Artemisia asiatica. During our work, fungal endophytes were isolated from a medicinal plant, A. asiatica. The culturable endophytic fungi were identifi ed using molecular techniques and biodiversity, richness and tissue specifi city were examined. As these microorganisms have been generally identifi ed as an abundant reservoir of novel antimicrobial compounds, the antimicrobial (i.e. antibacterial and antifungal) activities of the metabolites produced by the isolated fungi were studied. Numerous extracts containing the endophytic metabolites proved to be active against the applied test microorganisms including Gram-positive and Gramnegative bacteria, as well as yeasts and fi lamentous fungi, which can be examined in detail in the future and, based on the the chemical nature of these active metabolites, allow to discover novel bioactive metabolites