Microbial pigments: Eco-friendly extraction techniques and some industrial applications

Since ancient times, natural coloring agents have been produced from plants, insects, animals, and ores. Although they have a dangerous impact on mammals and the environment, synthetic dyes replace natural colors because of their limited availability throughout the year; instability in light, heat, and pH; increased global demand; and low water solubility. Therefore, pigments from microbial sources are considered the best alternatives to natural pigments. The potential of microbial pigments for easy mass production, diversified coloring properties, and inexpensive production is now receiving the attention of researchers and industries. Most industrial extraction processes are based on traditional liquid-liquid systems that use organic solvents for the extraction of pigments. The environmental pollution generated by these chemicals has become a central issue in societal and political decisions. This has led to a growing demand for efficient eco- friendly extraction technologies. In the last two decades, significant advances have been made in the green chemistry of pigment extraction and separation techniques. Methods such as ultrasound-assisted extraction, microwave-assisted extraction, pressurized liquid extraction, enzyme-assisted extraction, and more recently, ionic liquid-assisted extraction have been developed. This review summarizes the methods for the simple and eco -friendly extraction of microbial pigments for applications in the food and textile sectors.