Genomic and functional characterization of pyomelanin production by Shewanella indica biofilms on 3D-printed scaffolds for dye removal

Inspired by the interactions between sponges and bacteria within marine ecosystems, this study presents a scalable platform for the production of pyomelanin utilizing Shewanella indica immobilized on three-dimensional (3D) printed gyroid spheres with a surface area of 1835 mm². The application of five gyroid spheres immobilized with S. indica in 100 ml of growth medium resulted in a yield of 0.937 mg ml⁻¹ of pyomelanin, which could be enhanced to 3.76 mg ml⁻¹ when utilizing 20 spheres. The extraction of pyomelanin was accomplished through an alkali-acid treatment, and the gyroid spheres demonstrated reusability over five cycles. Furthermore, the pyomelanin exhibited an adsorption capacity of up to 70% for various textile dyes, including crystal violet and trypan blue, within a three-hour period. Genomic analysis identified genes associated with biofilm formation (lap A, B; lol A, B, D, E; DGC and bdl A) and pyomelanin biosynthesis (hppD, aspC, tyrA, and phhA). These results underscore a sustainable approach for pyomelanin production and its potential applications in bioremediation.