Integrated nitrate bioremediation and microbial risk mitigation using Bacillus pacificus.

The release of nitrate-rich effluents and pathogens from domestic and industrial sources into drinking water sources poses a significant environmental and public health challenge. The present study evaluates the multifunctional potential of the Gram-positive bacterium Bacillus pacificus (Accession No. PV206819) as a sustainable bioagent for nitrate remediation and antimicrobial risk reduction within a circular bioeconomy framework. The nitrate removal efficiency corresponds to 65.8% at 27 °C and 85.7% at 37 °C, respectively. Transient accumulation of nitrite ions indicates the probable occurrence of the heterotrophic denitrification pathway. The application of bacteria for the denitrification of fertilizer wastewater resulted in a nitrate removal efficiency of 67%. To promote resource recovery, biomass recovered after treatment was utilized for the green synthesis of silver oxide nanoparticles (B-Ag2ONPs). The biosynthesized nanoparticles have unique surface plasmon resonance and were roughly spherical, polydisperse, and 15-20 nm in size. DLS measurement showed a size of 35.74 nm, and the surface charge was -2.17 mV. FTIR analyses confirmed the role of biological functional groups involved in capping and synthesis. B-Ag2ONPs exhibited significant antibacterial activity against a Gram-negative (E. coli ATCC 25922) indicator microorganism with a minimum inhibitory concentration of 17.52 mg/L. Phytotoxicity assessment indicated reduced toxicity of treated wastewater on wheat seeds (Triticum aestivum L.). Overall, this integrated bioprocess offers a sustainable solution for nitrate and microbial contamination, supporting environmental protection and public health in line with SDG 3 (Good Health and Well-Being) and SDG 6 (Clean Water and Sanitation).