Natural Pigments From Micrococcus aloeverae and Exiguobacterium aestuarii Strain as Sustainable Textile Dyes.

Abstract

Pigments, used as colouring agents for centuries, can be derived from nature or synthesized in labs. However, artificial dyes often pose health and environmental risks, leading to increased interest in natural pigments, particularly those from bacteria. This study investigates extracting and characterizing natural pigments from Micrococcus aloeverae (orange pigment) and Exiguobacterium aestuarii (yellow pigment). The pigments were extracted using methanol and stability was analysed using the CIELAB (International Commission on Illumination) scale. The extracted pigments were purified through thin layer chromatography (TLC) and column chromatography and analysed by Fourier transform infrared spectroscopy (FTIR) and liquid chromatography tandem mass spectrometry (LCMS/MS), revealing key compounds including roseophilin, tryptanthrin, vulgaxanthin II, nectriachrysone, and menaquinone-7 carboxylic acid. Stability tests indicated that the pigments were most stable at neutral pH but degraded under extreme pH, heat, and light, with the orange pigment showing greater stability. The two pigments were applied to three different fibres that is, cotton, Eri silk, and Mulberry silk. Both the pigments showed a strong affinity for mulberry silk. Optimal dyeing conditions for both the pigments were pH: 3.0 at 60°C for 40 min, resulting in excellent colour fastness to washing, light, and rubbing. This study suggests that the orange and yellow pigments from M. aloeverae and E. aestuarii could be effective natural colorants, with potential applications in textiles and other industries.