Biochromatic potential of Pseudomonas aeruginosa from grapes: molecular profiling, antimicrobial action and eco-friendly dye applications

Microorganisms represent an emerging and sustainable reservoir of naturally derived colorants with immense biotechnological and industrial significance. Owing to their superior biodegradability, environmental benignity, and renewable nature, microbial pigments offer a compelling alternative to conventional synthetic dyes, which are often associated with ecological toxicity and health hazards. The present investigation was undertaken to isolate, characterize, and evaluate a blue-green pigment synthesized by a bacterial strain recovered from black grape samples. The pigment-producing isolate was taxonomically characterized as Pseudomonas aeruginosa based on comprehensive biochemical profiling and confirmed through 16 S rRNA gene sequencing. The pigment, designated as SK4, was efficiently extracted using chloroform as the solvent system. The antimicrobial efficacy of the purified pigment was assessed against four clinically relevant human pathogens—Salmonella typhi, Pseudomonas aeruginosa, Escherichia coli, and Klebsiella pneumoniae—exhibiting inhibition zones of 12.06 mm, 13.03 mm, 10.00 mm, and 11.03 mm, respectively, thereby demonstrating notable broad-spectrum activity. Furthermore, the potential application of this microbial pigment as a biocolourant was evaluated by dyeing diverse textile substrates, including silk, cotton, crepe, and satin. The dyed fabrics were subsequently examined for colour fastness parameters encompassing washing, rubbing, light, and thermal stability, alongside cytotoxicity assessments to ensure biosafety. Among the tested fabrics, crepe demonstrated superior fastness properties with wash and rubbing ratings of 5 and 4, respectively. Satin exhibited moderate to good fastness (wash 4, rub 3), whereas silk and cotton showed comparatively lower performance. Light fastness was the limiting factor, with ratings ranging from 1 to 2 for all substrates. Collectively, the study underscores the technological promise of P. aeruginosa-derived pigment as an eco-compatible and economically viable biodye, capable of supplanting hazardous synthetic colorants in the textile industry due to its non-toxic nature, robust dyeing performance, and environmental sustainability.