Development of ecofriendly and reliable processes for the synthesis of nanoparticles has attracted considerable interest in nanotechnology because of its tremendous impetus in modulating metals into nanosize to their potential use for human benefits. In this study an endophytic fungus, Penicillium sp., isolated from healthy leaves of Curcuma longa (turmeric) was subjected to extracellular biosynthesis of silver nanoparticles (AgNps) and their activity against MDR E. coli and S. aureus. The biosynthesized AgNps optimization was studied and characterized by UV-visible spectroscopy, Fourier transform infrared spectroscopy (FTIR), and transmission electron microscopy (TEM). Then produced AgNps were tested against MDR E. coli and S. aureus. The endophytic fungus Penicillium sp. from healthy leaves of C. longa (turmeric) was found to be a good producer of AgNps. Parametric optimization showed maximum absorbance of 420–425 nm at pH-7, 25°C with 1 mM AgNO3 concentration and 15–20 g of wet biomass. Further TEM revealed the formation of spherical, well-dispersed nanoparticles with size ranging between 25 and 30 nm and FTIR shows the bands at 1644 and 1538 cm−1 corresponding to the binding vibrations of amide I and II bands of proteins, respectively. Antibacterial activity against MDR E. coli and S. aureus showed good results showing maximum zone of inhibition of 17 mm and 16 mm, respectively, at 80 µL of AgNps.

Silver Nanoparticles (AgNPs), the real silver bullet, are known to have good antibacterial properties against pathogenic microorganisms. In the present study AgNPs were prepared from extracellular filtrate of Aspergillus niger. Characterization of AgNPs by UV-Vis spectrum reveals specific surface plasmon resonance at peak 416 nm; TEM photographs revealed the size of the AgNPs to be 20–55 nm. Average diameter of the produced AgNPs was found to be 73 nm with a zeta potential that was −24 mV using Malvern Zetasizer. SEM micrographs showed AgNPs to be spherical with smooth morphology. EDS revealed the presence of pure metallic AgNPs along with carbon and oxygen signatures. Of the different concentrations (0, 2.5, 5, 10, and 15 μg/mL) used 10 μg/mL were sufficient to inhibit 107 CFU/mL of E. coli. ROS production was measured using DCFH-DA method and the the free radical generation effect of AgNPs on bacterial growth inhibition was investigated by ESR spectroscopy. This paper not only deals with the damage inflicted on microorganisms by AgNPs but also induces cell death through the production of ROS released by AgNPs and also growth kinetics of E. coli supplemented with AgNPs produced by A. niger.

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The present study deals with the transformation of L-tyrosine to L-dopa by Acremonium rutilum, a fungal tyrosinase producer, isolated from decomposed banana stud. This appears to be the first report on A. rutilum as a polyphenoloxidase producer with both cresolase and catecholase activity. Enriched Czapek-Dox agar was used for plate assay screening. Enriched potato dextrose broth was used for optimization studies, which induced high levels of L-dopa under submerged fermentation. A. rutilum gave the maximum L-dopa production (0.89 mg/ml) and tyrosinase activity (1095 U/mg) under the optimized parameters, that is, a temperature of 25 degrees C, pH 5.5, an inoculum size of 2.5 ml, and an incubation time of 72-120 h, with L-tyrosine (5 mg/ml) as substrate. Five resolved bands, with R(f) values of 0.73, 0.60, 0.54, 0.37, and 0.26, were observed, which confirmed the presence of L-dopa. This study involves the elevated profile of L-dopa production. Such study is needed, as L-dopa has the ability to control Parkinson's disease.

Aim:This study aims to evaluate the antibacterial efficacy of biosynthesized silver nanoparticles (AgNPs) produced using the fungi against Enterococcus faecalis biofilm model on root dentin.Materials and Methods:AgNPs were biosynthesized using the fungi Fusarium semitectum isolated from healthy leaves of Withania somnifera. Minimum inhibitory concentration (MIC) of AgNPs was determined by microbroth dilution method using series of dilutions. MIC dose was standardized to evaluate the antibacterial efficacy. For biofilm model, thirty root dentin blocks prepared using human extracted single-rooted teeth were inoculated with E. faecalis in Trypticase soy agar broth for 2 weeks with alternate day replenishment and randomly divided into three groups (n = 10 each) and treated as: Group I: Sterile distilled water, Group II: AgNPs, and Group III: 2% chlorhexidine gluconate (CHX) and incubated at 37°C for 24 h. Each dentin block was rinsed in saline, vortex shaken for 60 s, and serial decimal dilutions were prepared and plated on trypticase soy agar plates and incubated for 24 h followed by CFU colony counting and statistically analyzed using one-way ANOVA followed by post hoc Tukey honestly significant difference test.Results:MIC of AgNPs for E. faecalis was determined as 30 mg/ml. No significant difference was seen between AgNPs and 2% CHX when compared to the control group with mean colony counts being 2.4, 2.5, and 6.77 CFU/ml (107), respectively (P < 0.0001), against E. faecalis biofilm.Conclusion:Biosynthesized AgNPs exhibit effective antimicrobial activity against E. faecalis biofilm on root dentin. Therefore, it can be employed as antimicrobial agent for root canal disinfection.