Exploring pigment-producing Streptomyces as an alternative source to synthetic pigments: diversity, biosynthesis, and biotechnological applications. A review.

The increasing health and environmental concerns associated with synthetic pigments have intensified the global search for natural, eco-friendly alternatives. Among microbial sources, Streptomyces, a genus within the class Actinomycetia, has emerged as a prolific source of bioactive pigments with wide-ranging industrial applications. The review provides a comprehensive synthesis of pigment-producing Streptomyces, focusing on their ecological diversity, biosynthetic pathways, and taxonomic relevance. This review has discussed key pigment classes, including melanin, prodiginine, quinone, and actinorhodin, with their bioactive properties, such as antioxidants, antimicrobials, and anticancer. The review further emphasizes recent advancements in synthetic biology, including clustered regularly interspaced short palindromic repeats/CRISPR-associated (CRISPR/Cas)-based gene editing, which has facilitated the activation of silent biosynthetic gene clusters (BGCs) that can enhance pigment yield. Additionally, this review discusses the optimization and fermentation protocols, industrial scalability, and the application of pigments in food, pharmaceutical, cosmetic, textile, and environmental sectors. Despite these advancements, critical research gaps persist, particularly in toxicological evaluation, pigment stability under industrial conditions, high-throughput screening of unexplored Streptomyces strains, and the integration of AI-based predictive tools for pathway optimization. Addressing these gaps is essential to unlocking the full potential of Streptomyces-derived pigments to replace harmful synthetic colorants.