Research Articles

Modes of antibacterial action of the extract from edible brown algae Ascophyllum nodosum against food spoilage bacteria Pseudomonas fluorescens and Shewanella putrefaciens were investigated. The colony forming units in P. fluorescens and S. putrefaciens were 0.70 and 1.03 log cfu/mL less than the negative control in the time-kill assay, indicating the inhibitory effect of the extract on the two bacteria at high cell density. The extract also inhibited the extracellular protease activity of the two bacteria, where the exopolysaccharide (EPS) content was reduced by 44.8% in P. fluorescens and 64.7% in S. putrefaciens after treating them with the extract of the minimum inhibition concentration (MIC). Reduction in live bacteria cells in the biofilm formed by the two bacteria strains exposed to 1×MIC and 2×MIC levels was also observed. Significant increase in 260-nm absorbing material, protein content, and electrical conductivity of the culture media was observed after 6-h incubation with the extract in both bacteria strains, suggesting a leakage of nucleic material, protein, and other intracellular constitutes. It was concluded that the extract of A. nodosum could exert antibacterial activity against P. fluorescens and S. putrefaciens by reducing their extracellular enzymatic activity, inhibiting EPS production and biofilm formation, and increasing cell permeability.

The objective of this study was to shorten the drying time of wood material using microwave and infrared + microwave drying methods, compare the energy assumption, analyze their improvement in water absorption, and compare the compression strength perpendicular and parallel to fibers. Red pine (Pinus brutia) and Eastern spruce (Picea orientalis) woods were prepared in three groups. The first group was oven dried, the second group was dried by microwave, and the third group was dried by infrared + microwave methods. The analysis results for energy consumption, moisture content, and compression strength perpendicular and parallel to the fibers were performed. Compression strengths were determined with a universal testing device. According to the results obtained, with 15 min microwave drying, 4% moisture content was reached in the wood samples and both time and energy were saved. It was observed that oven drying consumed 93% more energy than 15 min microwave drying. Samples dried with infrared 30 s + microwave 5 min had higher compression strength in the direction perpendicular to the fibers and samples dried with microwave for 5 min had higher compression strength in the direction parallel to the fibers.

The thermal conductivity was measured for Al₂O₃ nanofluid using a newly developed polymeric base fluid. The novel base fluid of cross-linked polyacrylic acid (PAA) solutions was synthesized via radical polymerization using a distinct deep eutectic solvent (DES). Five weight concentrations of Al₂O₃ nanoparticles, 0.05, 0.10, 0.15, 0.20, and 0.25 wt%, were dispersed in the polymeric fluid via two dispersing techniques. In the first step, the nanoparticles were stirred using magnetic stirring for 1 h, followed by the sonication technique for another hour to ensure the nanoparticles were well suspended in the base fluid. A KD2 Pro thermal analyzer measured the thermal conductivity of each concentration for the temperature from 30 to 70 °C. The experimental data demonstrated a correlation between thermal conductivity and nanoparticle weight fraction. The results showed that the thermal conductivity increased with the increment of Al₂O₃ concentration for all set temperatures. The study revealed that the polymeric base fluid could replace the conventional base fluid since the thermal conductivity results were comparable with those reported in the literature.

This study aimed to assess the chemical composition, specifically metal content, phenolics, and fatty acids, of two bryophyte species, Polytrichum formosum and Polytrichum commune, which belong to the Polytrichaceae family. The bioactivities of these species were also evaluated. Microwave plasma atomic emission spectroscopy was used to analyze 13 elements, revealing the presence of 10 elements at varying concentrations in both species. Iron (Fe) was the most prominent element in P. formosum, with a concentration of 7610 mg/kg, whereas calcium (Ca) was the most prominent element in P. commune, at a concentration of 8430 mg/kg. The high-performance liquid chromatography mass spectrometry analysis revealed the presence of 53 phenolic compounds, with quinic acid, protocatechuic acid, and fisetin being the most prominent with concentrations of 4.45, 2.26, and 1.46 mg analyte/g extract, respectively. When evaluated for total phenolic content, P. commune had a higher concentration of phenolic compounds than P. formosum. The fatty acid profile obtained via gas chromatography-mass spectrometry analysis revealed higher concentrations of oleic acid (36.6% for P. formosum and 38.0% for P. commune) and palmitic acid (35.5% for P. formosum and 33.8% for P. commune). Three independent assays assessed the antioxidant capacities of both plants, which revealed significant antioxidant potential in both species.