Enhanced detection of antimicrobial activities and secondary metabolites production from Plantactinospora sp. KBS50 cultivated using the OSMAC fermentation approach

Aims: A rare marine-derived actinomycete, Plantactinospora sp. KBS50, has been identified as a potential source of bioactive secondary metabolites compounds. The present study aimed to evaluate the secondary metabolites biosynthetic capability of strain KBS50 using the One Strain Many Compound (OSMAC) fermentation strategy. Methodology and results: Strain KBS50 was fermented in a basal medium (ISP2) supplemented with selected biological and chemical elicitors, as well as cultivation at different pH value and incubation temperature. Statistical analysis revealed that the antimicrobial activities were significantly increased, as compared to the basal medium, ISP2. Similarly, the comparative High Performance Liquid Chromatography (HPLC) analysis showed an increase in secondary metabolites production, as well as the detection of potential new metabolites, particularly from the crude extracts of ISP2 medium supplemented with 1% (w/v) sodium chloride and with the culture filtrate of Aspergillus niger. The bioassay-guided fractionation showed that the extract of strain KBS50 contains multiple compounds with antibacterial activity against the Gram-positive strains. Further fractionation led to the isolation of two semi-pure compounds (compound 3 and 4) with bactericidal properties against Staphylococcus aureus. The Minimum Inhibitory Concentration (MIC) values of compound 3 and 4 were recorded at 7.81 mu g/mL and 62.50 mu g/mL, respectively. The minimum bactericidal concentration (MBC) for compound 3 was recorded at 15.63 mu g/mL while the MBC for compound 4 was recorded as 125.00 mu g/mL. Conclusion, significance and impact of study: The OSMAC fermentation strategy used in this study had successfully enhanced the detection of antibiotics and secondary metabolites from Plantactinospora sp. KBS50. The bioassay-guided fractionation further established the capability of strain KBS50 as a source of bioactive secondary metabolite compounds with potent antimicrobial activity.