Phytofabrication of Silver Nanoparticles Using Trigonella foenum-graceum L. Leaf and Evaluation of Its Antimicrobial and Antioxidant Activities.

Silver nanoparticles (AgNPs) were fabricated using Trigonella foenum-graceum L. leaf extract, belonging to the variety HM 425, as leaf extracts are a rich source of phytochemicals such as polyphenols, flavonoids, and sugars, which function as reducing, stabilizing, and capping agents in the reduction of silver ions to AgNPs. These phytochemicals were quantitatively determined in leaf extracts, and then, their ability to mediate AgNP biosynthesis was assessed. The optical, structural, and morphological properties of as-synthesized AgNPs were characterized using UV-visible spectroscopy, a particle size analyzer (PSA), FESEM (field emission scanning electron microscopy), HRTEM (high-resolution transmission electron microscopy), and FTIR (Fourier transform infrared spectroscopy). HRTEM analysis demonstrated the formation of spherically shaped AgNPs with a diameter of 4-22 nm. By using the well diffusion method, the antimicrobial potency of AgNPs and leaf extract was evaluated against microbial strains of Staphylococcus aureus, Xanthomonas spp., Macrophomina phaseolina, and Fusarium oxysporum. AgNPs showed significant antioxidant efficacy with IC50 = 426.25 µg/mL in comparison to leaf extract with IC50 = 432.50 µg/mL against 2,2-diphenyl-1-picrylhydrazyl (DPPH). The AgNPs (64.36 mg AAE/g) demonstrated greater total antioxidant capacity using the phosphomolybdneum assay compared to the aqueous leaf extract (55.61 mg AAE/g) at a concentration of 1100 µg/mL. Based on these findings, AgNPs may indeed be useful for biomedical applications and drug delivery systems in the future.

Biosynthesis of Silver Nanoparticles Utilizing Leaf Extract of Trigonella foenum-graecum L. for Catalytic Dyes Degradation and Colorimetric Sensing of Fe3+/Hg2.

The aqueous Trigonella foenum-graecum L. leaf extract belonging to variety HM 444 was used as reducing agent for silver nanoparticles (AgNPs) synthesis. UV-Visible spectroscopy, Particle size analyser (PSA), Field emission scanning electron microscopy coupled to energy dispersive X-ray spectroscopy (FESEM-EDX) and High-resolution transmission electron microscopy (HRTEM) were used to characterize AgNPs. Selected area electron diffraction (SAED) confirmed the formation of metallic Ag. Fourier Transform Infrared Spectroscopy (FTIR) was done to find out the possible phytochemicals responsible for stabilization and capping of the AgNPs. The produced AgNPs had an average particle size of 21 nm, were spherical in shape, and monodispersed. It showed catalytic degradation of Methylene blue (96.57%, 0.1665 ± 0.03 min-1), Methyl orange (71.45%, 0.1054 ± 0.002 min-1), and Rhodamine B (92.72%, 0.2004 ± 0.01 min-1). The produced AgNPs were excellent solid bio-based sensors because they were very sensitive to Hg2+ and Fe3+ metal ions with a detection limit of 11.17 µM and 195.24 µM, respectively. From the results obtained, it was suggested that aqueous leaf extract demonstrated a versatile and cost-effective method and should be utilized in future as green technology for the fabrication of nanoparticles.

Biosurfactant production prospects of a Gram-negative bacterium-Klebsiella pneumoniae ssp. ozaenae BK34.

Increasing environmental concerns have brought natural surfactant produced by microorganisms into limelight due to their lesser toxicity, biodegradable nature, and retention of activity at extreme conditions. In the present investigation, the surfactant production perspective of capsulated Gram-negative bacilli Klebsiella pneumoniae ssp. ozaenae BK34 was explored. It was identified on the basis of PCR amplification of conserved region of 16SrRNA using species specific primers. Highest oil displacement and emulsification (E24) index of 6.8 cm and 20% along with 4.38-fold increase in biomass were attained using olive oil (2% (v/v)) as substrate. Incorporation of urea at 0.5% (w/v) concentration increased the oil displacement, E24 index, and drop diameter to 9.2 cm, 77.50%, and 0.80 cm, respectively, accompanied by 5.38-fold increase in biomass production. Biosurfactant level was recorded maximum at 30 °C as apparent from the oil displacement of 9.3 cm and E24 index of 75%. Reduction in incubation temperature to 25 °C abated oil displacement (5.2 cm) and E24 index (17.66%). Biosurfactant production was also appeared to be pH sensitive as shifting pH from 7.0 to 6.0 or 8.0 reduced the E24 index from 75 to 35% and 25%, respectively. Inoculum of stationary phase bacterial biomass at the proportion of 0.05% (w/v) was found adequate in triggering maximum biosurfactant production while the log phase biomass delayed the production significantly. Acid precipitation method was able to yield 7 g/L biosurfactant at pH 2. The surfactant was allocated to glycolipopeptide class on the basis of FTIR spectroscopy.

Nanotechnology for Sustainable Agriculture: An Emerging Perspective.

The realm of agriculture has to confront an expansive gamut of challenges including climatic change, stagnant crop yield and the increasing resistance against pesticides. The explicit usage of agrochemicals along with the introduction of high yielding varieties and genetically modified seeds has already directed the agricultural systems towards a state of saturation in production. Therefore, the increasing need of sustainability demands the involvement of advanced nanotechnological approaches for enhancing crop productivity. Enhanced solubility, absorption and target specificity of nannofertilizers prepared using materials like silver, copper, gold and oxides of zinc and iron could address some of nutritional challenges. Nanopesticides such as chitosan loaded with spino sad, silica encapsulating fipronil and sodium alginate enclosing imidacloprid find applications in pest control while fluorescence nanosensor, carbon and graphene nanodots are exploited in herbicide and heavy metal detection. Nanofilteration involving grapheme, cellulose and cyclodextrin for removal of salt, heavy metals and organic pollutants, respectively, could significantly improve quality of hard and waste water making it suitable for irrigation.