Green silver nanoparticle (AgNP) biosynthesis is facilitated by the enzyme mediated reduction of Ag ions by plants, fungi and bacteria. The antimicrobial activity of green AgNPs is useful to overcome the challenge of antimicrobial resistance. Antimicrobial properties of biosynthesized AgNPs depend on multiple factors including culture conditions and the microbial source. The antimicrobial activity of AgNPs biosynthesized by ATCC 27853, ATCC 25922, ATCC 25923 and (confirmed clinical isolate) were investigated in this study. Biosynthesis conditions (AgNO concentration, pH, incubation temperature and incubation time) were optimized to obtain the maximum AgNP yield. Presence of AgNPs was confirmed by observing a characteristic UV-Visible absorbance peak in 420-435 nm range. AgNP biosynthesis was optimal at 0.4 g/L AgNO concentration under alkaline conditions at 60-70 °C. The biosynthesized AgNPs showed higher stability compared to chemogenized AgNPs in the presence of electrolytes. AgNPs synthesized by were the most stable while NPs of were the least stable. AgNPs synthesized by and showed good antimicrobial potential against MRSA and. AgNPs synthesized by had greater antimicrobial activity. The antimicrobial activity of NPs may vary depending on the size and the morphology of NPs.

Titanium dioxide (TiO2) is commonly applied in food industry, cosmetics and pharmaceuticals due to its photocatalytic activity, stability, optical and electronic properties and biocidal activity. TiO2 nanoparticles (NPs) can be synthesized by conventional chemical, physical and biological methods. In this study, TiO2 NPs were biosynthesized using Baker's yeast (Y-TiO2) and characterized by X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM) and Energy Dispersive X-ray analysis (EDX). Antimicrobial activity was studied using plate coating method with and without sunlight exposure. XRD pattern confirmed the formation of pure anatase TiO2 nanoparticles. The porous surface of yeast cells act as the site for Ti 3 + nucleation. According to EDX data, Ti (Atomic percentage of 20.89%), O (70.95%), P (5.78%) and N (2.38%) were the key elements in the sample. TEM imaging revealed that the nanoparticles were spherical with an average size of 6.7 ± 2.2 nm. The photocatalytic activity of TiO2 NPs was studied by monitoring the degradation of Methylene blue dye. Fifty percent of dye degradation was observed within 15 min of UV exposure. This study is the first report on antimicrobial study of yeastmediated TiO2 NPs synthesized using TiCl3. Antimicrobial activity of TiO2 nanoparticles was high against selected Gram positive bacteria and Candida albicans compared to Gram negative bacteria in the presence or absence of exposure to sunlight. The percentage reduction of colony forming units (CFU/mL) after exposure to Y-TiO2 NPs following 30 min of sunlight exposure significantly reduced S. aureus ATCC 25923 (77%), MRSA clinical isolate (97%) and C. albicans ATCC 10231 (95%) compared to the control due to the photocatalytic activity. The percentage reduction of CFU/mL for gram negative bacteria P. aeruginosa ATCC 27853, E. coli ATCC 25922 and A. baumannii clinical isolate were 58%, 46% and 50% respectively after exposure to sunlight. Y-TiO2 NPs showed antimicrobial activity in the absence of exposure to sunlight under room conditions. After 30 min of contact with Y-TiO2 NPs, percentage inhibition of S. aureus (20%), MRSA (25%), C. albicans (74%), P. aeruginosa (30%), E. coli (26 %) and A. baumannii (23%) were lower compared to sunlight exposure. Sunlight exposure has enhanced antimicrobial activity of TiO2 NPs. The outcomes indicate the significant physical properties and the impact of yeast-mediated TiO2 nanoparticles as a novel antimicrobial.

BACKGROUND Silver nanoparticles (AgNPs) are increasingly being used in medical applications. Therefore, cost effective and green methods for generating AgNPs are required.OBJECTIVES This study aimed towards the biosynthesis, characterisation, and determination of antimicrobial activity of AgNPs produced using Pseudomonas aeruginosa ATCC 27853.METHODS Culture conditions (AgNO3 concentration, pH, and incubation temperature and time) were optimized to achieve maximum AgNP production. The characterisation of AgNPs and their stability were evaluated by UV-visible spectrophotometry and scanning electron microscopy.FINDINGS The characteristic UV-visible absorbance peak was observed in the 420–430 nm range. Most of the particles were spherical in shape within a size range of 33–300 nm. The biosynthesized AgNPs exhibited higher stability than that exhibited by chemically synthesized AgNPs in the presence of electrolytes. The biosynthesized AgNPs exhibited antimicrobial activity against Escherichia coli, P. aeruginosa, Salmonella typhimurium, Staphylococcus aureus, methicillin-resistant S. aureus, Acinetobacter baumannii, and Candida albicans.MAIN CONCLUSION As compared to the tested Gram-negative bacteria, Gram-positive bacteria required higher contact time to achieve 100% reduction of colony forming units when treated with biosynthesized AgNPs produced using P. aeruginosa.

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SDstandard deviation *Nystatin (25 µg/ml) Secondary phytochemicals including alkaloids, flavonoids, steroids, saponins, tannins and chalcones were detected in the root, leaf and stem aqueous extracts.Conclusions: Plumbago zeylanica root extract has shown the highest antimicrobial activity when compared to leaf and stem extracts. It was most effective against C. albicans showing higher antifungal activity. The antibacterial property of these plant extracts could be mainly due to their phenolic and flavonoid content.