Antimicrobial Efficacy of Biogenic Cobalt and Copper Nanoparticles against Pathogenic Isolates

Biogenic synthesis of cobalt (Co) and copper (Cu) nanoparticles (NPs) was performed using the bacterial strains Escherichia coli and Bacillus subtilis. Prepared NPs were confirmed by a color change to maroon for CoNPs and green for CuNPs. The NPs characterization using FTIR showed the presence of functional groups, i.e., phenols, acids, protein, and aromatics present in the Co and CuNPs. UV-vis spectroscopy of E. coli and B. subtilis CuNPs showed peaks at 550 and 625 nm, respectively. For E. coli and B. subtilis CoNPs, peaks were observed at 300 nm and 350 nm, respectively. Antibacterial and antifungal activity of B. subtilis and E. coli Co and CuNPs was determined at 100 mg/mL concentration against two bacterial strains at 5, 2.5, and 1.5 mg/mL against fungal two strains F. oxysporum and T. viridi, respectively. B. subtilis CuNPs showed significantly higher inhibition zones (ZOI=25.7-29.7 mm) against E. coli and B. subtilis compared to other biogenic NPs. Likewise, B. Subtilis CuNPs showed lower MIC (4.3 ± 6.3) and MBC (5.3 mg/mL) values against both tested isolates. Antifungal activity of B. subtilis and E. coli CuNPs and CoNPs showed a concentration-dependent decrease in ZOI. Among all biogenic NPs, B. subtilis CoNPs showed the highest ZOI (25-30 mm) against F. oxysporum followed by E. coli CuNPs with maximum ZOI (20-27 mm) against T. viridi. Again, B. subtilis CoNPs and E. coli CuNPs showed lowest MIC and MFC values against both fungal isolates. In conclusion, the current study showed that biogenically synthesized B. subtilis Cu or CoNPs can be used as effective antimicrobial agents due to their potential antibacterial and antifungal potential.