Bioproduction Optimization, Characterization, and Bioactivity of Extracellular Pigment Produced by Streptomyces parvulus.

Actinomycetes, especially Streptomyces, are prolific producers of bioactive metabolites, including pigments with potential applications in foods, textiles, cosmetics, and pharmaceuticals. Motivated by increasing concerns about the safety and environmental impact of synthetic pigments, this study aimed to optimize the production of an extracellular pigment-rich fraction from Streptomyces parvulus and to evaluate its bioactivities relevant for cosmeceuticals. A Plackett-Burman design was used to identify key variables influencing metabolite production, followed by optimization with a Box-Behnken design. The pigment-rich fraction was obtained after extraction with ethyl acetate from lyophilized supernatants and chemically characterized by IR and LC-MS. Biological assays were conducted to assess anti-tyrosinase, immunomodulatory, and antimicrobial activities. Temperature, incubation time, and agitation speed were identified as the most significant factors, with optimal conditions of 30 °C, 50 rpm, and 7 days yielding a pigment concentration of 465.3 μg/mL. LC-MS analysis revealed three 1,4-naphthoquinone-containing compounds, annotated as juglomycin Z (1), WS-5995B (2), and naphthopyranomycin (3), as the main constituents. The pigment-rich fraction showed modest anti-tyrosinase activity (10.9% at 300 μg/mL), immunomodulatory effects (TNF-α inhibition up to 36.9% and IL-10 stimulation up to 38.4% in macrophages), and antimicrobial activity against Staphylococcus epidermidis (15.8 mm inhibition halo, 91% growth reduction). The optimized fermentation model enhances pigment yield while reducing resource consumption, and the pigment-rich fraction exhibits multifunctional bioactivities, underscoring its potential as a natural cosmeceutical ingredient.