Acta Microbiologica Bulgarica

69-80

Authors: Adebayo-Tayo B. C., Ogunrinade J. O.

The study aims to investigate the biosynthesis and characterization of gold (AuNPs) and sil¬ver nanoparticles (SNPs) using biomolecules: exopolysaccharides (EPS), culture-free filtrate (CFF) and fruiting body extract (FBE) of Pleurotus ostreatus (PO), and to evaluate the antibacterial potential of the nanoparticles against some pathogens. The nanoparticles were characterized by UV-visible spectra, FTIR and SEM. Nanoparticles formation was confirmed by changes in colour; colour changes from pale yellow to purple, cloudy colourless to purple and yellow to dark purple indicate, respectively, POEPSAuNPs, POCFFAuNPs and POFBEAuNPs formation. Colour changes from pale yellow, cloudy colourless and yel¬low to dark brown indicate POEPSSNPs, POCFFSNPs and POFBESNPs formation, respectively. Surface plasmon resonance (SRP) peaks were observed at 400 nm. SEM revealed POEPSAuNPs, POCFFAuNPs and POCFFAuNPs as polymorphic with sizes ranging from 0.5 – 2.6 μm, 0.08 - 1.00 μm, and 0.2 – 2.4 μm. POEPSSNPs, POCFFSNPs and POFBESNPs were aggregate particles with sizes of 0.2 - 3.0 μm, 0.2 - 2.8 μm, and 0.1 – 3.2 μm. FTIR showed that amide, carboxyl and hydroxyl groups contributed to nanoparticles biosynthesis. The AuNPs exhibited a broad spectrum of activity against the tested pathogens compared to the SNPs. POEPSAuNPs and POFBEAuNPs had the highest inhibitory activity against E. coli while POF¬BEAuNPs had the highest inhibitory activity against Micrococcus sp. with MIC of 0.2 at 200 μg/mL, and POEPSSNPs and POCFFSNPs had the highest inhibitory activity against S. aureus with MIC of 0.05 at 50 μg/mL. In conclusion, biomolecules from P. ostreatus supported the biosynthesis of nanoparticles with enhanced therapeutic properties.

88-94

Authors: Dishliyska V., Stefanova L., Atev A.

Aspergillus oryzae is well known species and it has an important role in the fermentation of oriental food products and in industrial application as a producer of hydrolytic enzymes. An extracellular α-amy¬lase enzyme from mutant strain A. oryzae MSPP was purified to electrophoretic homogeneity by a simple procedure including ammonium sulfate precipitation, anion-exchange chromatography and Sephadex gel filtration. All purification steps were checked by PAGE. The molecular mass of the purified α-аmylase was estimated to be 52 kDa. The enzyme had a pH optimum at 4.7 and was stable in the range of pH 4.7 to 10. The optimal temperature for the highest α-amylase activity was measured at 50˚C. Half-life of the enzyme was 30 min at 50˚C. Stability of the purified enzyme mainly depended on the presence or absence of soluble starch in the reaction mixture. Michaelis constant (Km) for soluble starch as a substrate was estimated to be 5 mg/ml.

98-100

Authors: Petrov N., Ivanova V.

Systemic Acquired Resistance (SAR) against Potato Virus Y (PVY) was induced in pepper plants us¬ing natural elicitors based on salicylic acid. Treatment of pepper plants with elicitors induced SAR against PVY infection, which resulted in a reduction in DAS-ELISA values and viral symptoms in plants caused by PVY. Treatment of pepper plants with a combination of two elicitors 3 days before virus inoculation induced strong PVY resistance in the experimental pepper plants.