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.

Surfactins are cyclic lipopeptides consisting of a β-hydroxy fatty acid of various chain length and a peptide ring of seven amino acids linked together by a lactone bridge, forming the cyclic structure of the peptide chain. These compounds are produced mainly by Bacillus species and possess numerous biological effects such as antimicrobial (antiviral, antibacterial, and antifungal) activities. A mixture of surfactins extracted from Bacillus subtilis strain SZMC 6179J was examined by HPLC-ESI-IT-MS technique, enhancing their separation to reveal novel lipopeptide varieties with higher masses and to characterize their structures. During the MS2 spectra analyses of their sodiated molecular ions [M + Na]+, a previously rarely encountered group of surfactins was detected and two novel types of the group were discovered containing methyl esterified aspartic acid residue in their fifth amino acid position. The relative amounts of these monomethyl isoforms exceeded 35% of the produced surfactin in total. In the m/z value of 1114, all the detected isoforms possessed aspartic acid 4-methyl ester residue in their fifth amino acid position (C17-[Lxx4, AME5], C18-[AME5]), offering an opportunity to separate a pure fraction of the compound and to study its biological activities in the future.

White button mushroom—Agaricus bisporus (J.E.Lange) Imbach—is among the most popular cultivated mushrooms worldwide. The most serious challenge in industrial mushroom production is the green mold disease caused by Trichoderma species. Our aim was to isolate and examine bacterial strains from mushroom casing material for their potential use as biocontrol agents. Twenty-seven bacterial strains were isolated and tested against mold pathogens of white button mushroom. The Bacillus velezensis strain SZMC 25431 was selected for further examination and tested under simulated Agaricus cultivation conditions against T. aggressivum SZMC 23834 in a 1200-L Fitotron SGC120 standard plant growth chamber. Our results showed that the bacterial treatment was effective against the pathogen in all cases, but the best results were achieved at an application concentration of 105 cells mL−1. Industrial-scale experiments were also carried out in Agaricus growing houses with a bearing surface of 480 m2: the bacterial suspension was mixed in water tanks applied for daily irrigation. The results suggest that the bacterial treatment may even increase the crop yield of A. bisporus. Based on our results, we concluded that the selected B. velezensis strain may potentially be used for biological and integrated treatment in Agaricus cultivation.

Surfactins are cyclic lipopeptides consisting of a β-hydroxy fatty acid of variable chain length and a peptide ring of seven amino acids linked together by a lactone bridge, forming the cyclic structure of the peptide chain. These compounds are produced mainly by Bacillus species and are well regarded for their antibacterial, antifungal, and antiviral activities. For their surfactin production profiling, several Bacillus strains isolated from vegetable rhizospheres were identified by their fatty acid methyl ester profiles and were tested against phytopathogen bacteria and fungi. The isolates showed significant inhibition against of E. amylovora, X. campestris, B. cinerea, and F. culmorum and caused moderate effects on P. syringae, E. carotovora, A. tumefaciens, F. graminearum, F. solani, and C. gloeosporioides. Then, an HPLC-HESI-MS/MS method was applied to simultaneously carry out the quantitative and in-depth qualitative characterisations on the extracted ferment broths. More than half of the examined Bacillus strains produced surfactin, and the MS/MS spectra analyses of their sodiated precursor ions revealed a total of 29 surfactin variants and homologues, some of them with an extremely large number of peaks with different retention times, suggesting a large number of variations in the branching of their fatty acid chains.

Surfactins are lipopeptide-type biosurfactants produced mainly by Bacillus species containing a peptide loop of seven amino acids and a hydrophobic fatty acid chain. These molecules exhibit various biological activities; therefore, their therapeutic and environmental applications are in the focus worldwide. In our work, a multi-step purification and separation process was developed to isolate surfactins from the ferment broth of B. subtilis SZMC 6179J strain. The process incorporates normal phase flash chromatography for pre-purifying the crude extract and two consecutive reverse phase HPLC separations for the isolation of the various surfactin molecules. The determination of the relative amounts of lipopeptides both in the crude extract and in each fraction of every separation step were carried out by HPLC-HESI-MS examinations. The ratio of surfactins in the crude extract was 21.35%, but after the preparative flash chromatographic separation the relative amount of surfactins was observed to be 30.44%. The preparative HPLC purification step resulted 85.39% purity of the surfactins. Nine different surfactin variants were isolated and identified from the fractions of this final semi-preparative HPLC purification, out of which three compounds were completely purified, and three others were detected in relative amounts of more than 95% in some fractions.