The synthesis and antibacterial properties of silver nanoparticles mediated by biosurfactant

Biological methods for nanoparticle synthesis are gaining increasing recognition due to their ability to enhance the biocompatibility of nanoparticles for biomedical and environmental applications. Surface modification via biotechnology to improve the biocompatibility of nanoparticles is an effective strategy. In this study, the synthesis of biosurfactant-silver nanoparticles (BS32-AgNPs) was mediated by lipopeptide biosurfactant as capping agents and stabilizers. The antimicrobial mechanisms and antibacterial properties of BS32-AgNPs were also explored. The results showed that the average particle size of BS32-AgNPs was 26 nm, exhibiting a face-centered cubic structural characteristic and high stability and dispersibility, with a Zeta potential value of -51.4 mV. BS32-AgNPs demonstrated significant antimicrobial activity, with minimum inhibitory concentration of 7.5 mg/l and 15 mg/l against E. coli DH5 alpha (G(-)) and B. borstelensis (G(+)), respectively. Scanning electron microscope and transmission electron microscopy observations revealed that the antimicrobial mechanism of BS32-AgNPs involves adsorption onto the bacterial surface, interacting with the cell membrane, increasing membrane permeability, and ultimately leading to membrane disruption and cell death. Further experimental evaluation of the antimicrobial activity of BS32-AgNPs against sulfate-reducing bacteria (SRB) showed that at a concentration of 120 mg/l, the functional genes dsrB and aprA of encoding SRB accounted for nearly 0% of the total bacterial population, which demonstrates the stable and potent antimicrobial activity of BS32-AgNPs. Moreover, it provides a green and efficient new method for the suppression of SRB in oil reservoir environments.