Unveiling Carbon Dioxide and Ethanol Diffusion in Carbonated Water-Ethanol Mixtures by Molecular Dynamics Simulations
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ABSTRACT:
SUBMITTER: Ahmed Khaireh M
PROVIDER: S-EPMC8003404 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Simple Summary The consumption of bottled mineral water has been rising in the last decades. During the water bottling process, the risk of bacterial contamination with pathogen bacteria is a well-known problem. In this study, the influence of different carbon dioxide concentrations, in mineral water bottles, on the growth of Staphylococcus aureus and Enterococcus faecalis was investigated. Inside an Austrian mineral water bottling factory, a sum of 160 glass bottles with different carbon dioxide concentrations (3.0 g/L, 5.5 g/L, and 7.0 g/L) were capped after artificial contamination, stored at room temperature (20 °C), kept away from light, and dried in the laboratory. Water samples from freshly opened bottles were filtrated and cultivated on agar media to determine the number of colony-forming units over a period of 30 days. After the 23rd day, no more cultivable bacteria were detected in the samples from the freshly opened bottles. This observation leads to the conclusion that carbonated mineral water is an inappropriate habitat for Staphylococcus aureus and Enterococcus faecalis. Abstract During the process of mineral water production, many possible contamination settings can influence the quality of bottled water. Microbial contamination can originate from different sources, for example, the ambient air, the bottles, the caps, and from the bottling machine itself. The aim of this study was to investigate the influence of three different carbon dioxide (CO2) concentrations (3.0 g/L, 5.5 g/L, and 7.0 g/L; 20 bottles each) in bottled mineral water on the bacterial growth of Staphylococcus aureus (S. aureus) and Enterococcus faecalis (Ent. faecalis). The examined mineral water was artificially contaminated before capping the bottles inside the factory. After a specific number of days, water samples were taken from freshly opened bottles and after filtration (100 mL), filters were placed on Columbia Agar with 5% Sheep blood to cultivate S. aureus and Slanetz and Bartley Agar to cultivate Ent. faecalis. The respective colony-forming units (CFU) were counted after incubation times ranging from 24 to 120 h. Colony-forming units of S. aureus were not detectable after the 16th and 27th day, whereas Ent. faecalis was not cultivable after the 5th and 13th day when stored inside the bottles. The investigation of the bottles that were stored open for a certain amount of time with CO2 bubbling out showed only single colonies for S. aureus after the 5th day and no CFUs for Ent. faecalis after the 17th day. A reduction in the two investigated bacterial strains during storage in carbonated mineral water bottles means that a proper standardized disinfection and cleaning procedure, according to valid hygiene standards of industrial bottling machines, cannot be replaced by carbonation.
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Project description:Rice husk, a rice processing byproduct generated in large quantities (∼20% of the grain weight), creates a major disposal problem for the rice industry. However, rice husk contains high-value bioactive compounds that can provide potential health benefits. The objective of this study was to extract high-value phenolic compounds from rice husk using supercritical carbon dioxide (SC-CO2) technology. In this study, the effects of different extraction conditions, namely, temperature (40 and 60 °C), pressure (30 and 40 MPa), and ethanol concentration (15 and 25%, w/w) on the total phenolic content (TPC), total flavonoid content (TFC), and antioxidant activity (AA) were investigated. The extraction of phenolic compounds was also studied using different SC-CO2 modifiers, i.e., ethanol and ethanol-water. The highest TPC, TFC, and AA were achieved with 30 MPa, 60 °C, and 25% ethanol-water (50%, v/v) cosolvent mixture as 1.29 mg gallic acid equivalent (GAE)/g, 0.40 mg catechin equivalent (CE)/g, and 0.23 mg Trolox equivalent (TE)/g, respectively. Increasing water content up to 50% (v/v) in the cosolvent significantly improved the extraction yield. p-Coumaric, ferulic, and syringic acids were the predominant phenolic acids in the extracts obtained by cosolvent-modified SC-CO2 and methanol extractions. In addition, ethanol-water-modified SC-CO2 increased rice husk's porosity, which could be a potential pretreatment to enhance cellulose extraction. Thus, ethanol-water-modified SC-CO2 can be utilized to recover polar bioactive compounds from food processing byproducts for developing functional foods while eliminating the use of toxic organic solvents.
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Project description:Lithium-carbon dioxide (Li-CO2) batteries are regarded as a promising electrochemical system owing to their energy storage capability and CO2 utilization. However, the reported operating voltage of ~2.6 V is increasingly questioned as seemingly beyond the capability of the electrochemical carbon dioxide reduction reaction to carbon. Herein, the real operating voltage of a Li-CO2 battery is reacquainted, and the operating voltage and the equilibrium potential are clarified to be ~1.1 V and ~2.82 V, respectively. The products formed at low voltage are identified to be crystalline Li2CO3, amorphous C, and explicitly amorphous Li2CO3. Moreover, by decoupling small currents, 1% O2, and 500 ppm H2O, the operating voltage plateaus are stimulated to ~2.0 V. An ever-increasing plateau can be achieved up to the reported level of ~2.6 V activated by a minor air leak or residue in test environments. Conclusively, the operating voltages of Li-CO2 batteries are proposed to be deceptive and extremely sensitive to the surrounding environments. This work unveils the real operating voltage and provides the voltage regulation rules to advance next-generation Li-CO2 batteries.
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Project description:We present investigations into remote liquid temperature sensing with Raman spectroscopy using different evaluation methods for the OH stretching vibration band. Water, ethanol, and ethanol saturated with nitrogen, all as liquids or liquid-like supercritical fluids, are pumped through a heated microcapillary system at elevated pressures. Raman spectra are recorded from the liquid inside the microcapillary and are evaluated with respect to the temperature sensitivity of the OH stretching vibration. The four approaches applied are (i) to evaluate the center position of the Raman OH-band, (ii) the integrated absolute difference spectrum, (iii) the intensity ratio of two regions of the OH-band, and (iv) the intensity ratio of two fitted Gaussian peaks. The temperature range investigated covers from ambient temperature to the component's respective boiling temperature or critical temperature at sub- and supercritical pressures. Precision and robustness of the employed methods are characterized. It is shown that two out of the four methods feature temperature deviations smaller than 5 K at all pressures and that one method can also be applied to liquid mixtures of ethanol and nitrogen. Applicability to other liquids and mixtures is discussed.
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