Fungal xylanases‐mediated synthesis of silver nanoparticles for catalytic and biomedical applications

Green synthesis of nanoparticles has fuelled the use of biomaterials to synthesise a variety of metallic nanoparticles. The current study investigates the use of xylanases of Aspergillus niger L3 (NEA) and Trichoderma longibrachiatum L2 (TEA) to synthesise silver nanoparticles (AgNPs). Characterisation of AgNPs was carried out using UV–Vis spectroscopy, Fourier transform infrared spectroscopy (FTIR), and transmission electron microscopy, while their effectiveness as antimicrobial, antioxidant, catalytic, anticoagulant, and thrombolytic agents were determined. The colloidal AgNPs was brownish with surface plasmon resonance at 402.5 and 410 nm for NEA‐AgNPs and TEA‐AgNPs, respectively; while FTIR indicated that protein molecules were responsible for the capping and stabilisation of the nanoparticles. The spherical nanoparticles had size of 15.21–77.49 nm. The nanoparticles significantly inhibited the growth of tested bacteria (63.20–88.10%) and fungi (82.20–86.10%), and also scavenged DPPH (37.48–79.42%) and hydrogen peroxide (20.50–96.50%). In addition, the AgNPs degraded malachite green (78.97%) and methylene blue (25.30%). Furthermore, the AgNPs displayed excellent anticoagulant and thrombolytic activities using human blood. This study has demonstrated the potential of xylanases to synthesise AgNPs which is to the best of our knowledge the first record of such. The present study underscores the relevance of xylanases in nanobiotechnology.Inspec keywords: visible spectra, catalysis, ultraviolet spectra, silver, microorganisms, antibacterial activity, transmission electron microscopy, surface plasmon resonance, nanoparticles, nanofabrication, colloids, blood, Fourier transform infrared spectra, particle sizeOther keywords: Ag, fungal xylanases‐mediated synthesis, silver nanoparticles, catalytic applications, biomedical applications, green synthesis, metallic nanoparticles, Trichoderma longibrachiatum L2, transmission electron microscopy, antimicrobial agents, antioxidant agents, catalytic agents, thrombolytic agents, surface plasmon resonance, spherical nanoparticles, FTIR spectra, anticoagulant agents, colloidal nanoparticles, biomaterials, Aspergillus niger L3, UV‐vis spectroscopy, Fourier transform infrared spectroscopy, protein molecules, DPPH, hydrogen peroxide, malachite green, methylene blue, human blood, nanobiotechnology     

Some inhibitory effects of radiation stress on tomato fruit ripening

Detached tomato (Lycopersicon esculentum Mill. cv. Vendor) fruit exposed to 650 W m^?2 radiation from incandescent lamps for 1.5 or 4 h developed visible injury during subsequent storage. In tissues directly exposed to the radiation, ascorbic acid content was decreased and lycopene accumulation and protopectin solubilisation were blocked. For intact fruit, the respiratory climacteric was depressed, but ethylene production was enhanced following the radiation stress. Radiation injury blocks both the initiation and the progress of ripening.     

Inhibitory effect of Garcinia kola on lipid peroxidation in rat liver homogenate

Garcinia kola, (a herb grown in Nigeria; calorific value 358.54 k.cal/100 g) inhibited in vitro lipid peroxidation of rat liver homogenate in a dose dependent manner. The inhibitory activity of G.kola was not affected by heating (100 degrees C/10 min). The antioxidant component of G.kola was soluble in aqueous and ethanolic media. The active component(s) in G. kola responsible for its inhibitory activity on lipid peroxidation is tentatively identified as isoflavones.     

Effects of sodium metabisulphite, hydrogen peroxide and heat on aflatoxin B1 in lafun and gari--two cassava products.

Sodium metabisulphite and hydrogen peroxide alone or in combination with heat (50-70 degrees C) were found to be effective in degrading aflatoxin B1 (AFB1) in lafun and gari. Hydrogen peroxide (H2O2) at a concentration of 3% in the aqueous phase gave a 12.5% degradation of aflatoxin B1 in lafun and at 50 degrees C, degradation levels of 25% and 50% were obtained with 6.0 and 9.0% H2O2, respectively. When sodium metabisulphite was applied during the production of gari (a fermented cassava product heated to 50-70 degrees C during production) AFB1 degradation levels were found to be 65.8%, 60.9%, 41.5% and 36.6%, respectively, for sodium metabisulphite levels of 1.0%, 0.8%, 0.5% and 0.3%.     

Servant leadership, procedural justice climate, service climate, employee attitudes, and organizational citizenship behavior: A cross-level investigation.

This study tests the influence of servant leadership on 2 group climates, employee attitudes, and organizational citizenship behavior. Results from a sample of 815 employees and 123 immediate supervisors revealed that commitment to the supervisor, self-efficacy, procedural justice climate, and service climate partially mediated the relationship between servant leadership and organizational citizenship behavior. Cross-level interaction results revealed that procedural justice climate and positive service climate amplified the influence of commitment to the supervisor on organizational citizenship behavior. Implications of these results for theory and practice and directions for future research are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Control of microbial growth, browning and lipid oxidation by the spice Aframomum danielli

Aframomum danielli   (family Zingiberaceae) for Listeria monocytogenes LCDC 81861 was 390 ppm. No viable cells were found after a 4 h exposure of Bacillus cereus (initial concentration 10³ cfu/ml) to 500 ppm of A. danielli (aqueous solution) when the concentration of untreated control cells was 3.9×10⁶ cfu/ml. The MICs of A. danielli for some food spoilage yeasts (Candida tropicalis, Hansenula anomala, Torulopsis candida and Kluveromyces thermotolerans) ranged from 100 to 200 ppm. Exposure of McIntosh apple slices at 25°C for 4 h to a crude powder of A. danielli (17000 ppm) and ascorbic acid (5000 ppm) produced comparative increased L* values and decreased a* values (antibrowning effect) as measured by reflectance spectroscopy. When crude antioxidant extract from A. danielli was added to refined soybean oil at 200 ppm, the antioxidant effectiveness (AE) was 70.7%, calculated from:

Effect of annealing on the functionality of Bambara groundnut (Vigna subterranea) starch–palmitic acid complex

Bambara groundnut is an underutilised African leguminous crop. This study investigated the effect of annealing on the complexing ability and functionality of Bambara groundnut starch with palmitic acid. Corn starch was included as the reference. Annealing created cracks and pores on the surface of Bambara groundnut and corn starches, respectively. Bambara groundnut starch had significantly higher amylose content, higher peak and final viscosities than corn starch. The peak viscosities of native Bambara groundnut and corn starches significantly reduced with palmitic acid addition. Greater reduction in peak viscosities was observed when the annealed starches were complexed with palmitic acid, suggesting that more palmitic acid was complexed after annealing. This was confirmed by XRD peaks and melting enthalpies. Pasting of native Bambara groundnut and corn starches with palmitic acid resulted in the formation of type I V‐amylose complexes, while type II complexes were formed from annealed starches pasted with palmitic acid.     

Characterization of fatty acid profile by FFFS

The purpose of the study was to assess potential application of front face fluorescence spectroscopy as a rapid and non-destructive technique to discriminate between fats of animal and plant origin based on their fatty acid profiles, and to predict concentration of fatty acids from fluorescence spectra. Vitamin E emission spectra (300–500 nm) of butterfat and vegetable oil samples were recorded with excitation wavelength set at 295 nm. Fatty acid composition of the samples was determined by gas chromatography. Principal component analysis and partial least squares regression analysis were applied to the gas chromatography and fluorescence spectroscopy data. The butter-fats and vegetable oils were discriminated based on the total saturated and unsaturated fatty acids respectively. Tocopherols and tocotrienols accounted for the variability among various oils. A good prediction model was established with R ² = 0.745–0.992 for saturated fatty acids. The unsaturated fatty acids were characterized by low coefficients of determination (R ² < 0.339). The fatty acid profiles predicted from fluorescence spectra did not show significant difference to those determined by gas chromatography used as references. A good association was established between the two data tables. The study demonstrated great potential of front face fluorescence spectroscopy to rapidly discriminate between fats of animal and plant origin, and predict their saturated fatty acids composition, which could in turn be used for detection of milk fat adulteration with vegetable oil.     

Protection of maize (Zea mays) and soybeans (Glycine max) using Aframomum danielli

When maize and soybeans were stored under ambient conditions (26ǃ °C/RH 75LJ%) using the ground material of the spice Aframomum danielli (family Zingiberaceae), mouldiness and insect infestation were controlled for 15 months. After eight weeks of storage, chemical compositions of maize and soybeans (moisture content, mc 10.0%) treated with 4.0%, 6.0% and 8.0% ground powder of A. danielli did not differ significantly (P=0.05) from those of untreated (control) samples. However, chemical compositions of samples maintained at 15.0% and 20.0% mc respectively were different from those of control samples (P>0.05). At 10.0% mc, maize and soybean samples treated with different concentrations of A. danielli powder were preferred to treated samples maintained at 15.0% and 20.0% respectively. The preservative capability of the powder of A. danielli was associated with phytochemical components tentatively identified as alkaloids. Viability of maize and soybeans was not affected by treatment with A. danielli powder. The powder of A. danielli has some protective effects on liver cells because it exerted no hepatotoxic effect on test albino rats as serum enzyme levels of glutamate oxaloacetate transmaminase (SGOT), glutamate pyruvate transaminase (SGPT) and alkaline phosphatase (ALP) were lowered by 67.0%, 86.3% and 49.7% respectively when compared with control albino rats not fed with A. danielli powder in their rations (meals).