Abstract
In the existing literature, there is ample information available concerning the analogs constituting linear Gramicidin (Gramicidin A). However, the literature lacks information regarding the microbial production of cyclic Gramicidin S (GR-S) and the study of its analogs' amino acid composition. Thus, in this study, GR-S was produced by Aneurinibacillus aneurinilyticus, isolated from corn steep liquor (CSL) and grown in synthetic or CSL-based medium. The extract was obtained from microbial biomass and underwent analysis with ultra performance liquid chromatography coupled with electrospray ionization tandem mass spectrometry (UPLC-ESI-MS/MS) to ascertain the presence and abundance of GR-S clusters, identifying five GR S analogs. Hence, when using a synthetic medium, the dominant cluster compromised the sequence Val-Orn-Leu-Phe-Pro-Val-Orn-Leu-Phe-Pro. Contrarily, when using CSL-based medium, the main analog was composed of Val-Orn-Leu-Phe-Pro-Val-Lys-Leu-Phe-Pro. In the remaining analogs, one or both Ornithine (Orn) residues were replaced by Lysine (Lys) or diaminobutyric acid (D-Dab). Microscopy images revealed that the use of CSL-based medium resulted in a lower yield of GR-S and a higher accumulation of vacuoles compatible with the presence of intracellular polyhydroxyalkanoates (PHA) when comparing with TSB medium. The antifungal assay revealed a superior conidial inhibition activity of GR-S extract under evaluation against Aspergillus brasiliensis in comparison to the commercial GR-S. Consequently, it can be concluded that this novel microbial GR-S extract exhibits favorable antifungal activity, positioning it as a promising candidate for antimicrobial treatments. However, further research is necessary to address the global challenge of antibiotic-resistant pathogens.