www.ejbps.com Kabo et al. European Journal of Biomedical and Pharmaceutical Sciences 135 BIOSYNTHESIS OF SILVER NANOPARTICLES WITH POTENT ANTIMICROBIAL ACTIVITY USING LACTIC ACID BACTERIA Kabo Ronald Wale* 1 , Wathuto Ogopotse 1 , Daniel Loeto 1 , Phatsimo Mokgweetsi 2 , Baemedi Letsholo 3 , Mbaki Muzila 1 , Krishna Behari Khare 1 and Ntebaleng Makate 1 1 Department of Biological Sciences, University of Botswana, Private Bag 0027, Gaborone, Botswana. 2 Department of Chemistry, University of Botswana, Private Bag 0027, Gaborone, Botswana. 3 Department of Environmental Sciences, University of Botswana, Private Bag 0027, Gaborone, Botswana. Article Received on 15/01/2019 Article Revised on 05/02/2019 Article Accepted on 26/02/2019 INTRODUCTION Over recent years, the rise of antimicrobial resistance among most medically important bacterial species has led to the urgent need for the development of new strategies to combat these organisms. Among them, nanoparticles have emerged as important candidates in the fight against infectious agents as well as many organisms that easily develop resistance to conventional antimicrobial substances. Nanoparticles are defined as particulate dispersions of solid particles with at least one dimension at a size range of 10-100 nm. [1] These nano sized particles have unique properties which give them the ability to be applied to many areas especially the medical field, the food industry and in waste water treatment. The most important feature of nanoparticles is their surface area to volume aspect ratio, resulting in appearance of new mechanical, chemical, electrical, optical, magnetic, electro-optical, and magneto-optical properties that are different from their bulk properties, thus allowing them to interact with other particles easier. [2] Silver nanoparticles (AgNPs) are one of the most studied among metallic nanoparticles as they have been proven to be effective antibacterial agents and possess a strong antimicrobial activity against bacteria, viruses and fungi. [3] This is because silver ions and silver-based compounds are highly toxic to a wide range of microorganisms including major species of drug resistant bacteria. Hence this aspect of silver makes it an excellent choice for multiple roles in the medical field. These nanoparticles of silver have been studied as a medium for antibiotic delivery [4] and to synthesize composites for use as disinfecting filters and coating materials. [5] SJIF Impact Factor 4.918 Research Article ejbps, 2019, Volume 6, Issue 3, 135-141. European Journal of Biomedical AND Pharmaceutical sciences http://www.ejbps.com ISSN 2349-8870 Volume: 6 Issue: 3 135-141 Year: 2019 *Corresponding Author: Kabo Ronald Wale Department of Biological Sciences, University of Botswana, Private Bag 0027, Gaborone, Botswana. ABSTRACT In this study, Lactic Acid Bacteria isolated from traditional fermented foods were screened for the synthesis of silver nanoparticles. Antimicrobial activity of the synthesized nanoparticles was assayed against several multi- drug resistant clinical human pathogenic bacteria. Among the bacterial isolates that were tested, K1.16 and MM17 had 99% and 98% relatedness with Lactobacillus herbarum strain TCF032 E4 and Lactobacillus paraplantarum strain DSM 10667 respectively, and were able to reduce silver efficiently into silver nanoparticles. The Ultraviolet–Visible spectrum showed a plasmon peak at ~ 410 nm confirming the presence of silver nanoparticles. Energy dispersive X-ray spectrum revealed a strong signal in the silver region confirming the formation of silver nanoparticles as well as a optical absorption peak at approximately 3 KeV due to surface plasmon resonance. Diffraction peaks were observed at 38.1°, 44.2°, 64.4° and 77.4° in the 2θ range. The peaks were indexed to (111), (200), (220) and (311) which can be indexed according to the facets of a face centered cubic crystal structure of silver. Scanning transmission electron microscope micrographs recorded from the coated grid of the synthesized nanoparticles showed a spherical shape of silver nanoparticles with the size range of 11-71 nm. Silver nanoparticles produced by Lactobacillus plantarum (K1.16) were the most potent as indicated by the lowest minimum inhibitory concentrations across all pathogenic bacterial isolates tested in this study, which included; Escherichia coli, Staphylococcus aureus, Klebsiella pneumoniae, Salmonella Typhimurium, Bacillus cereus and Enterobacter spp. These findings can be pertinent in the development of novel topical ointments against pathogenic microorganisms. KEYWORDS: Lactic acid bacteria (LAB), silver nanoparticles (AgNPs), antimicrobial, Energy dispersive x-ray (EDX), Scanning transmission electron microscope (STEM).