Biofabrication of isotropic silver nanoparticles using cell-free metabolic extract of Bacillus kochii, and evaluation of their antimicrobial, antioxidant and catalytic potentials

Abstract

Microbial metabolites have been reported as potent candidates in the biofabrication of nanomaterials. For the first time, the present study reported the biofabrication of ecofriendly isotropic silver nanoparticles (BkCE-AgNPs) showed potential antimicrobial, antioxidant and biocatalysts characteristics using the metabolite of Bacillus kochii. Further, B. kochii crude extract (BkCE) mediated synthesis of BkCE-AgNPs was confirmed by surface plasmon resonance (SPR) peak at 420 nm using a UV-vis spectrophotometer. Various major physico-chemical parameters such as temperature, pH, crude extract concentration, AgNO3 concentration were utilized to characterize BkCE-AgNPs. In addition, FTIR analysis revealed the functional groups of active compounds present in the BkCE that mediated the fabrication of BkCE-AgNPs. Whereas, HRTEM confirmed the synthesis of BkCE-AgNPs with a size range between 4 to 44 nm and the crystalline nature of the biofabricated BkCE-AgNPs was confirmed by EDAX. Furthermore, the BkCE-AgNPs exhibited a broad-spectrum antimicrobial activity against A. baumannii, S. typhi, E. coli, K. pneumoniae, S. aureus and P. aeruginosa. The BkCE-AgNPs also showed excellent catalytic dye degradation potential and antioxidant activities confirmed by DPPH assay, total reducing sugar test and nitric oxide scavenging assays. In conclusion, the present study could help understand the development of biofabrication of nanomaterials using potent microbial metabolites in the agricultural and medicinal industries.