Abstract
BACKGROUND: Actinomycetes are a diverse group of filamentous, Gram-positive bacteria recognized for their ability to produce various secondary metabolites, including pigments. These pigments have various industrial applications and safe alternatives to synthetic pigments associated with adverse side effects. This study aimed to investigate pigment-producing Actinomycetes from Sof-Umer cave rock and sediment samples, focusing on their potential applications. METHODS: Thirty isolates of Actinomycetes were selected based on their morphology and further screened based on their pigment diffusion ability. Through subsequent screening and characterization, three isolates designated AFSc1, AFSc6, and AFSc9 were identified as potent pigment-producing Actinomycetes. The pigment extracts from these isolates were tested for their antibacterial and antioxidant activities and also evaluated for use as fabric colorants. For further identification, the isolates were subjected to 16S rRNA gene sequencing, where AFSc1 showed 98.34% similarity to Curtobacterium flaccumfaciens, AFSc6 98.9% similarity to Rhodococcus cercidiphylli, and AFSc9 99.36% similarity to Arthrobacter species. RESULTS: The pigment extracts demonstrated significant antibacterial activity, with inhibition zones ranging from 18 ± 0.75 mm to 22 ± 0.88 mm against Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus. Notably, AFSc9 showed the highest antioxidant activity (IC50 value of 16.84 ± 0.56 µg/mL). The pigment extracts were efficiently fixed to the cotton fabrics. UV-spectrophotometric analysis revealed λ max values of 430 nm for AFSc1, 495 nm for AFSc6, and 426 nm for AFSc9. The Fourier-Transform Infrared Spectroscopy (FTIR) analyses indicated the presence of diverse functional groups, and GC-MS analysis identified 13 and 42 chemical compounds in the chromatograms of AFSc6 and AFSc9, respectively. CONCLUSION: In this study, the pigment extracts of the isolates showed remarkable antibacterial, antioxidant, and fabric colorant properties, emphasizing the potential of Sof-Umar cave-dwelling Actinomycetes as sources of natural colorants and bioactive compounds.