Pharmaceutical and Biotechnological Perspectives Regarding Melanin Pigment From Streptomyces spp.

Background and objective Melanin production is a distinguishing taxonomic and functional trait of <i>Streptomyces</i> species. The pigment exhibits antioxidant properties, making it relevant for use in medicine, cosmetics, and the food industry. Its potential in supporting health and mitigating oxidative stress highlights its value in various biotechnological applications. This study aimed to isolate melanin-producing <i>Streptomyces</i> strains from rhizosphere soil, characterize the pigment through biochemical tests, optimize production conditions, and explore its antioxidant, antimicrobial (against Gram-positive and Gram-negative pathogens), and bioremediation capabilities, as well as its role in nanoparticle synthesis. Methods Cultivation of the isolates was carried out using peptone-yeast extract, and tyrosine-casein agar media were employed for pigment screening. The pigment was tested for reactivity with L-tyrosine and L-dihydroxyphenylalanine (L-DOPA). Various carbon and nitrogen substrates were tested to assess their influence on pigment production. Antioxidant activity was assessed using the 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay, chosen for its simplicity, rapidity, and widespread use in evaluating radical-scavenging properties of natural pigments. Antimicrobial potential was tested against selected pathogens (including Gram-positive and Gram-negative bacteria). The biodegradation ability was examined through the decolorization of azo dyes. Biosurfactant activity and tolerance to heavy metals were also assessed. Additionally, crude pigment was utilized to facilitate the formation of copper nanoparticles, exploring potential applications in cancer-related studies. Each assay was conducted three times independently, and the obtained results are presented as mean ± standard deviation (SD) for statistical validity. Results The isolates were found to produce a diffusible pigment with coloration from dark brown to black that was soluble in water. It reacted positively with both L-tyrosine and L-DOPA. Optimization of media components led to increased pigment production. The final pigment was purified and exhibited significant antioxidant potential and was able to prevent the proliferation of bacterial and fungal test strains. Azo dyes were decolorized to a high level of 97.95, which means that the dyes are highly biodegraded. The strains were also biosurfactant active and had resistance to a range of heavy metals. The pigment was successfully synthesized into copper nanoparticles, and the biosynthesis of nanoparticles was verified using UV-Vis spectroscopy of the sample (absorbance peaks that are indicative of the nanoparticle formation), which further justifies the use of this pigment in therapeutic applications. Conclusions The strains of <i>Streptomyces</i> used in this study have shown several valuable characteristics of their pigment, which include antioxidant, antimicrobial, and pollutant-degrading capabilities. Based on this observation, the environmental, medical, and technological applications have various benefits that may be tapped.