Statistical bioprocess strategies for bio-fabrication of nano-ag from streptomyces rectiviolaceus strain SMWN3.2 as a novel antimicrobial agent against hospital-acquired infectious pathogens

Abstract

The application of actinomycetes for bio-fabrication of silver nanoparticles as a rapid, eco-friendly and promising approach is desired for its non-toxicity and simplicity advantages. From sixteen actinomycetes were isolated and checked for their ability to produce nano-Ag, Streptomyces rectiviolaceus strain SMWN3.2 showed more effective nano-Ag (surface plasmon resonance peak at 420 nm and its size 10nm) as an antimicrobial agent. Comparing with the biological process microbial nano-Ag synthesis have advantageous because of its natural abundance, easy culture and its potential to scale up for large scale synthesis, By using Plackett-Burman and Box-Behnken experimental designs the optimized medium components recorded the larger biomass production (16g/l) than the basal conditions (3.8 folds). Also, the optimal nano-Ag bio-fabrication conditions were 0.5M silver nitrate and 5v/v cell filtrate at 45°C. Kinetic conversion rates in submerged batch cultivation in 7L stirred bioreactor was: YX =30.5, Pmax =85.5g/l and YP = 42.6 at 30hr. The best nano-Ag concentrations that formed large inhibition zones were 35-60=g/ml and the MIC/MBC and MIC/MFC measured as 255∅ßg/ml/505∅ßg/ml, 505∅ßg/ml/605∅ßg/ml which showed against Streptococcus pneumoniae and Aspergillus fumigatus respectively. This work is focuses on large-scale production of nano-Ag as an antimicrobial agent against hospital-acquired infectious pathogens.