Waste to wealth: circular approaches for microbial pigment production

The increasing demand for natural and sustainable colorants has accelerated interest in microbial pigments as alternatives to synthetic dyes. Diverse microorganisms, including bacteria, fungi, yeasts, microalgae, and actinomycetes, produce pigments such as carotenoids, melanins, prodigiosin, violacein, and phycobiliproteins with applications in food, pharmaceuticals, cosmetics, textiles, and biomedicine. Despite their potential, large-scale microbial pigment production remains constrained by high costs, refined substrate dependency, and downstream processing challenges. This review summarizes recent advances in microbial pigment production using agro-industrial residues, food processing wastes, lignocellulosic biomass, and other organic waste streams within a circular bioeconomy framework. Key microbial sources, waste-derived substrates, and bioprocess strategies are discussed alongside techno-economic, environmental, and regulatory considerations. Current bottlenecks and emerging approaches, including metabolic engineering, synthetic biology, and integrated biorefinery concepts, are highlighted as future directions to enhance sustainability and industrial scalability.