Sustainable and Eco-friendly Nanoparticle Synthesis using Microbial Strains Isolated from Heavy Metal-rich Industrial Effluent

Introduction: The sustainable production of monodisperse metal nanoparticles is gaining global attention due to environmental concerns associated with conventional synthesis methods. Microbial biosynthesis offers an eco-friendly alternative, particularly when using strains adapted to heavy metal-rich environments. Methods: Microbial strains were isolated from the titanium industry effluent and screened for nanoparticle synthesis using cell-free culture supernatants. Cobalt and copper salt solutions were incubated with the supernatants at room temperature, neutral pH, and static conditions. Nanoparticle formation was monitored via colour change, UV-Vis spectroscopy and FTIR analysis. Results: Bacillus cereus and Curvularia sp. synthesized copper and cobalt oxide nanoparticles within 2 and 7 days, respectively. UV-Vis spectra showed sharp peaks at 341-342 nm, indicating a narrow size distribution. FTIR confirmed functional groups involved in nanoparticle stabilization. Over 1 gram of cobalt oxide nanoparticles was obtained from 25 mL of Curvularia culture supernatant. Discussion: Monodisperse nanoparticles were successfully synthesized using cell-free supernatants of effluent-adapted microbes without the need for heating, surfactants, or toxic reagents. The sharp UV-Vis peaks, indicative of uniform particle size, remained stable even after one week, highlighting the nanoparticles’ stability. The findings indicated stable, monodisperse nanoparticle formation, while the eco-friendly synthesis method supported scalability. Conclusion: This study has presented a novel and scalable method for cobalt oxide and copper nanoparticles synthesis using microbes from the titanium industry effluent. The method has been found to be energy-efficient, sustainable, and capable of producing monodisperse nanoparticles under ambient conditions, highlighting its potential for green nanotechnology applications.