Ameliorated Antibacterial and Antioxidant Properties by Trichoderma harzianum Mediated Green Synthesis of Silver Nanoparticles.

Biosynthesis of silver nanoparticles using beneficial Trichoderma harzianum is a simple, eco-friendly and cost-effective route. Secondary metabolites secreted by T. harzianum act as capping and reducing agents that can offer constancy and can contribute to biological activity. The present study aimed to synthesize silver nanoparticles using T. harzianum cell filtrate and investigate different bioactive metabolites based on LC-MS/MS analysis. The synthesized silver nanoparticles (AgNPs) from T. harzianum were characterized by ultraviolet-visible spectrophotometry, Fourier transform infrared spectrometry (FT-IR), energy-dispersive spectroscopy (EDS), dynamic light scattering (DLS), X-ray powder diffraction (XRD) and scanning electron microscopy (SEM). The surface plasmon resonance of synthesized particles formed a peak centered near 438 nm. The DLS study determined the average size of AgNPs to be 21.49 nm. The average size of AgNPs was measured to be 72 nm by SEM. The cubic crystal structure from XRD analysis confirmed the synthesized particles as silver nanoparticles. The AgNPs exhibited remarkable antioxidant properties, as determined by DPPH and ferric reducing antioxidant power (FRAP) assay. The AgNPs also exhibited broad-spectrum antibacterial activity against two Gram-positive bacteria (S. aureus and B. subtilis) and two Gram-negative bacteria (E. coli and R. solanacearum). The minimum inhibitory concentration (MIC) of AgNPs towards bacterial growth was evaluated. The antibacterial activity of AgNPs was further confirmed by fluorescence microscopy and SEM analysis.

Bioactive compounds guided diversity of endophytic fungi from Baliospermum montanum and their potential extracellular enzymes.

Baliospermum montanum (Willd.) Muell. Arg, a medicinal plant distributed throughout India from Kashmir to peninsular-Indian region is extensively used to treat jaundice, asthma, and constipation. In the current study, 203 endophytic fungi representing twenty-nine species were isolated from tissues of B. montanum. The colonization and isolation rate of endophytes were higher in stem followed by seed, root, leaf and flower. The phytochemical analysis revealed 70% endophytic isolates showed alkaloids and flavonoids, 13% were positive for phenols, saponins and terpenoids. Further, these endophytes produced remarkable extracellular enzymes such as amylase, cellulase, phosphates, protease and lipase. The most promisive three endophytic fungi were identified by ITS region and secreted metabolites were identified by gas chromatography-mass spectrometry (GC-MS/MS). The GC-MS profile detected twenty-five bioactive compounds from ethyl acetate extracts. Among endophytic fungi, Trichoderma reesei isolated from flower exhibited nine bioactive compounds namely, 2-Cyclopentenone, 2-(4-chloroanilino)-4-piperidino, Oxime-methoxy-Phenyl, Methanamine N-hydroxy-N-methyl, Strychane, Cyclotetrasiloxane, Octamethyl and 1-Acetyl-20a-hydroxy-16-methylene. The endophyte, Aspergillus brasiliensis isolated from root and Fusarium oxysporum isolated from seed produced nine and seven bioactive compounds, respectively. Overall, a significant contribution of bioactive compounds was noticed from the diverse endophytic fungi associated with B. montanum and could be explored for development of novel drug with commercial values.

Detection and Characterization of Antibacterial Siderophores Secreted by Endophytic Fungi from Cymbidium aloifolium.

Endophytic fungi from orchid plants are reported to secrete secondary metabolites which include bioactive antimicrobial siderophores. In this study endophytic fungi capable of secreting siderophores were isolated from Cymbidium aloifolium, a medicinal orchid plant. The isolated extracellular siderophores from orchidaceous fungi act as chelating agents forming soluble complexes with Fe3+. The 60% endophytic fungi of Cymbidium aloifolium produced hydroxamate siderophore on CAS agar. The highest siderophore percentage was 57% in Penicillium chrysogenum (CAL1), 49% in Aspergillus sydowii (CAR12), 46% in Aspergillus terreus (CAR14) by CAS liquid assay. The optimum culture parameters for siderophore production were 30 °C, pH 6.5, maltose and ammonium nitrate and the highest resulting siderophore content was 73% in P. chrysogenum. The total protein content of solvent-purified siderophore increased four-fold compared with crude filtrate. The percent Fe3+ scavenged was detected by atomic absorption spectra analysis and the highest scavenging value was 83% by P. chrysogenum. Thin layer chromatography of purified P. chrysogenum siderophore showed a wine-colored spot with Rf value of 0.54. HPLC peaks with Rts of 10.5 and 12.5 min were obtained for iron-free and iron-bound P. chrysogenum siderophore, respectively. The iron-free P. chrysogenum siderophore revealed an exact mass-to-charge ratio (m/z) of 400.46 and iron-bound P. chrysogenum siderophore revealed a m/z of 453.35. The solvent-extracted siderophores inhibited the virulent plant pathogens Ralstonia solanacearum, that causes bacterial wilt in groundnut and Xanthomonas oryzae pv. oryzae which causes bacterial blight disease in rice. Thus, bioactive siderophore-producing endophytic P. chrysogenum can be exploited in the form of formulations for development of resistance against other phytopathogens in crop plants.