Production of Natural Pigment from Bacillus subtilis KU710517 Using Agro-Industrial Wastes and Application in Dyeing of Wool Fabrics

A comparative study was performed between some waste materials to assess their ability to produce natural pigment from Bacillus subtilis KU710517 isolated from the marine sponge Pseudoceratina arabica. Bacillus subtilis KU710517 was able to produce a yellowish-brown pigment with wheat bran and molokhia stems in both water and synthetic media. Some factors affecting the pigment production by Bacillus subtilis KU710517 were studied. The pigments produced had been assessed for their use in dyeing wool fabrics (at a liquor ratio of 50:1 across various pH levels), and the color strength values of samples were examined. The highest color strength value of dyed wool fabrics was obtained when using water containing 6% molokhia stems (K/S 6.98) for 2 days at pH 9. Also, good fastness properties were obtained with molokhia stems. Therefore, the yellowish-brown pigment produced from Bacillus subtilis KU710517 is highly appropriate for dyeing and printing wool textiles and serves as a safe alternative to synthetic dyes that create environmental issues. Moreover, using waste materials and water in the production of dye is an economical and ecofriendly method. HPLC analysis of the pigment produced from molokhia stems in a water medium indicated the presence of rutin and syringic acid, which are responsible for the yellowish-brown color. The antimicrobial properties of the produced pigment were examined with the cup agar diffusion technique. Nutrient agar plates were inoculated with 0.1 mL of 105–106 cells/mL of yeast and bacteria. Czapek-Dox agar plates were heavily inoculated with 0.1 mL (106 cells/mL) of fungal culture. 100 microliters of the dye sample were added to each cup. The pigment showed considerable antimicrobial activity against bacteria, yeast, and fungi and displayed the strongest antimicrobial activity against E. coli (28 mm zone of inhibition). Therefore, the produced pigment can be used in the pharmaceutical field, especially in the dyeing of surgical dressings and clothing.