Physico-cultural parameters during AgNPs biotransformation with bactericidal activity against human pathogens

Production of AgNPs with desired morphologies and surface characteristics using facile, economic and non-laborious processes is highly imperative. Cell extract based syntheses are emerging as a novel technique for the production of diverse forms of NPs, and is assured to meet the requirements. Therefore, in order to have a better understanding, and to improvise and gain control over the NPs morphological and surface characteristics, the present investigation systematically evaluates the influence of various major physico-cultural parameters including diverse growth media, concentrations of precursor salts; pH and temperature on the biotransformation of ionic silver (Ag⁺) to nanopariculate silver nanoparticles (AgNPs), utilizing the cell free extract of the bacterium, P. plecoglossicida. The synthesis, purity, morphology and surface characteristics of the AgNPs during optimization studies were measured. The bactericidal effect of these AgNPs was assessed using multi-drug resistant human pathogens; Acinetobacter baumannii, Escherichia coli, Pseudomonas aeruginosa and Salmonella enterica based on the diameter of inhibition zone in disk diffusion tests. The nanoparticles were found to be of higher toxicity to E. coli and S. enterica than A. baumannii and P. aeruginosa. The results demonstrate that the chosen parameters in whole or in part could have a significant influence on the morphology, surface characteristics, duration of production, overall yield and production of AgNPs.