SYNTHESIS, CHARACTERIZATION, ANTIMICROBIAL AND ELECTROCHEMICAL STUDIES OF BIOSYNTHESIZED ZINC OXIDE NANOPARTICLES USING THE PROBIOTIC BACILLUS COAGULANS (ATCC 7050)

Abstract

Nowadays, nanotechnology has been used to overcome many global problems such as growing worldwide demand for energy and problems of microbial antibiotic resistance. The presented study used the probiotic Bacillus coagulans (ATCC 7050) as a nano-factory for the biosynthesis of zinc oxide nanoparticles (ZnO NPs). UV-visible spectroscopy, FTIR spectroscopy, XRD, TEM and Zeta analysis confirmed the formation of spherical ZnO NPs with a mean size of 10-19 nm and positive potential of 29±2 mV. The biosynthesized ZnO NPs showed potent antimicrobial activity against Gram-positive and Gram-negative bacteria as well as pathogenic yeast with minimum inhibition concentration (MIC) values of 500 and 800 μg/ml against Staphylococcus aureus ATCC 25923 and Pseudomonas aeruginosa ATCC 27853 and 600 μg/ml against Candida albicans ATCC 10231. On the other hand, a voltaic cell composed from an immersed reduced copper (positive electrode) and platinum electrodes (negative electrode) in ZnO NPs/bacterial metabolites was connected to a voltameter and used to study the electrochemical activity of ZnO NPs/B. coagulans metabolites. Electrochemical characterization of ZnO NPs/B. coagulans metabolites was done using current density–voltage characteristic, power density and electrochemical impedance spectroscopy (EIS) analyses. ZnO NPs/B. coagulans metabolites produced high current with voltage value ≈ >0.34 volt. The present study reported the ability of B. coagulans to produce nitrate reductase enzyme with enzyme activity 2.18 U/ml. The reduction pathway of nitrate (NO₃^-) into nitrite (NO₂^-) during the biosynthesis of ZnO NPs might help and stimulate the current production.