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Chitosan/polyvinylpyrrolidone composite films containing hydroalcoholic Ziziphora clinopodioides extract were developed and evaluated for their potential use as wound dressings. The physical and chemical properties of the films were extensively explored, including swelling capacity, mechanical properties, antimicrobial activity, and microstructural characteristics. The results showed that the addition of Ziziphora extract significantly increased the swelling capacity of the films by 561.24% to 1175% (p < 0.05). While tensile strength and Young's modulus were enhanced, elongation at the breaking point decreased with increasing volume percentages of Ziziphora extract. Variance analysis indicated no statistically significant effect on the tensile properties of the films with varying Ziziphora extract content (p < 0.05). Furthermore, films incorporated with Ziziphora extract demonstrated antimicrobial properties. Scanning electron microscopy (SEM) analysis revealed that samples lacking Ziziphora extract had a smooth surface, while those containing the extract displayed a rough texture that may potentially accelerate the wound healing process. [ABSTRACT FROM AUTHOR]

Industrial processes do not often deal with a pure fluid. Impurities can affect physical properties of gas-liquid systems, resulting in change of gas bubbles velocity. Purpose of the study was to determine drag coefficient of a bubble rising through a contaminated fluid. As well as, a comparison was done between conditions of a free rising bubble and a rising bubble in wall-bounded flow. Thus, the behavior of a single air bubble rises in aqueous rhamnolipid solutions within two columns with different dimensions was studied experimentally. The experiments were conducted at high Reynolds numbers compared to other researches. The results revealed that effect of the surfactant in wall-bounded flow was much less than free flow whereas bubble terminal velocity was close to the one in a pure fluid and independent of concentration. Moreover, terminal velocity of the free rising bubble decreased as the solution concentration increased for the one less than critical micelle concentration. After that, it kept constant. Furthermore, resulted drag coefficient did not change significantly in different biosurfactant concentrations. The results showed that in high Reynolds number, drag coefficient was a function of Eötvös number and independent of Reynolds and Morton numbers. Consequently, two empirical correlations were presented to predict the terminal velocity and drag coefficient based on surface tension and Eötvös number, respectively. [ABSTRACT FROM AUTHOR]

A potent biosurfactant-producing bacterial strain isolated from spoiled apples was identified by 16S rRNA asPseudomonas aeruginosaMA01. Compositional analysis revealed that the extracted biosurfactant was composed of high percentages of lipid (66%, w/w) and carbohydrate (32%, w/w). The surface tension of pure water decreased gradually with increasing biosurfactant concentration to 32.5 mN m−1with critical micelle concentration (CMC) value of 10.1 mg L−1. The Fourier transform infrared spectrum of extracted biosurfactant confirmed the glycolipid nature of this natural product. Response surface methodology (RSM) was employed to optimize the biosynthesis medium for the production of MA01 biosurfactant. Nineteen carbon sources and 11 nitrogen sources were examined, with soybean oil and sodium nitrate being the most effective carbon and nitrogen sources on biosurfactant production, respectively. Among the organic nitrogen sources examined, yeast extract was necessary as a complementary nitrogen source for high production yield. Biosurfactant production at the optimum value of fermentation processing factor (15.68 g/L) was 29.5% higher than the biosurfactant concentration obtained before the RSM optimization (12.1 g/L). A central composite design algorithm was used to optimize the levels of key medium components, and it was concluded that two stages of optimization using RSM could increase biosurfactant production by 1.46 times, as compared to the values obtained before optimization. [ABSTRACT FROM AUTHOR]