Bacterial pigments as sustainable and functional colorants in cosmetic applications: advances and prospects

The bacterial world is a promising source for the production of colored metabolites known as bacterial pigments. Synthetic dyes are responsible for health problems such as allergies, cancer, toxicity, and hyperactivity and for environmental issues such as pollution of waterways, disruption in aquatic ecosystems, inhibition of photosynthesis, and bioaccumulation in food chains. These concerns have provided the microbial world a chance of being used as a source of natural pigment for industrial applications, including cosmetics. Cosmetic products such as lipsticks, nail polishes, hair dyes, soaps, body washes, face washes, creams, and lotions utilize various colored compounds of chemical origin and may pose adverse effects on their unregulated or overuse. Bacterial pigments can be an alternate and sustainable option to replace these chemical moieties in these cosmetic products. Bacteria from diverse habitats with a broad scale of colors such as carotenoids, prodigiosin, melanin, violaceins, quinones, and indigoidines have been reported for their beneficial properties such as color, antioxidant, emulsifying, antiaging, and UV protection. These pigments have multiple shades and also possess nutritional and therapeutic properties. Although most of the information in this field is based on primary research at a laboratory scale and very limited attempts have been made to improve these bacterial strains and processes for enhanced pigment production, it highlights a significant scope for research and innovations in this field. The integration of advanced genetic and metabolic engineering technology such as CRISPR/Cas, along with the utilization of artificial intelligence and machine learning-based methods, can transform this field and boost pigment production. Therefore, the current review article aims to provide a state-of-the-art overview of bacterial pigments with the potential for application in cosmetic products. Moreover, it also highlights the existing challenges and outlines future research directions.