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The utilization of microalgae as a green carbon source for chemical production has attracted attention for its potential use in sustainable and climate-friendly solutions. This study investigates the growth of Dunaliella salina, a unicellular green microalga, in response to salinity variations and water and seawater addition to compensate for evaporation in open cultures. The impact of continuous and non-continuous water addition, as well as seawater addition, on the growth of D. salina was analyzed though tank tests. The results showed that different water-addition methods did not significantly influence cell concentrations, indicating the organism’s resilience to salinity changes. Continuous water addition maintained stable salinity levels at 12%, but required continuous monitoring, while non-continuous addition reduced the intervention frequency. The overall results showed that a salinity range between 12 and 15% did not affect microalgae growth, suggesting flexibility in evaporation-loss compensation methods based on cultivation-system specifics and resource availability. Maintaining consistent biomass regardless of the water-addition method used suggests sustainable production within the tested salinity range, with seawater addition making microalgae cultivation more adaptable to regions with varying water availability. Further research, including outdoor pilot tests, is recommended to validate and extend these findings to natural environments.

The microalga Dunaliella salina can produce antioxidants such as glutathione, which is an essential and powerful regulator of major cell functions. Changes in the glutathione concentration occur due to a microalga’s response to oxidative stress, which usually occurs when cells are exposed to environmental stressors or reach senescence. This study represents one of the few examples where changes in the glutathione concentration were tracked over the entire growth cycle of an alga. We found significant differences in the glutathione concentration depending on the growth stage. During the early lag growth phase, D. salina had relatively low levels of glutathione (190–280 µmol/1012 cell), which gradually increased as it entered the log phase (280–500 µmol/1012 cell) but then decreased as it entered the stationary phase (320–370 µmol/1012 cell). We also observed that the ratio between the reduced form of glutathione (GSH) and the oxidized form (GSSG) decreased with time, probably as a result of senescence or a lack of nutrients.

Microalgae are a source of carbohydrates, proteins and lipids. Thus, they can be considered as raw material to transition from current fossil fuel-based refineries to biorefineries. Microalgae harvesting is considered a major challenge in biomass production. There are several harvesting techniques, but the majority of them are either expensive or not effective. The harvesting method that we propose is sedimentation-induced by light blockage, taking advantage of the motility characteristics of certain microalgae. In this research, the halophilic microalgae Dunaliella salina was selected. Experiments were conducted under light and dark conditions to compare the sedimentation rates. Sedimentation behavior was measured by collecting data on the optical density and cell count under both light and dark conditions. The results showed that, under light conditions, the cell count in the middle of the flask decreased from 1 × 106 cell/mL to 5 × 104 cell/mL after 50 days. Under dark conditions sedimentation took less than 10 days for complete settlement. Leaving Dunaliella salina under dark conditions may constitute a promising harvest method as this provides a high recovery rate and requires low energy.

Abstract Purpose The microalgae Dunaliella salina is mainly cultivated as a source of natural β-carotene, but it can also be an important source of other nutrients such as protein, carbohydrate, and lipids. Harvesting and dewatering are considered the most expensive processes in the biomass production, so we proposed gravity sedimentation as a cost-effective method. The effect of temperature and dissolved oxygen concentration on the gravity sedimentation of normal cells and carotenoid-accumulating cells of Dunaliella salina was investigated in this study. Methods Dunaliella salina was cultivated in an f/2 culture medium at two different salinities, 12.5% (2.2 M NaCl) and 17.5% (3.3 M NaCl). Carotenoid-accumulating cells were cultivated in a medium without a nitrogen source by removing NaNO3 from the f/2 medium and at two different salinities, 12.5% and 17.5%. For gravity sedimentation tests, 10 mL of the suspended culture media were transferred to conical tubes and wrapped with aluminum foil for shading. The tubes were incubated at 4 °C, 10 °C, 15 °C, 20 °C, 25 °C, 30 °C, 35 °C, 40 °C, 45 °C, and 50 °C for 4 h and 18 h. For the gravity sedimentation under aerobic and anaerobic conditions, 10 mL of the suspended culture media were transferred to conical tubes and then purged with 20% oxygen and 80% nitrogen or 100% nitrogen for 10 min and wrapped with aluminum foil. The tubes were incubated at 25 °C for 0.5 h, 1 h, 2 h, and 3 h. Result Recovery rates differed with temperature, salinity, and time. The recovery rate of normal cells and carotenoid-accumulating cells reached 79 to 96% at 20 °C, 25 °C, and 30 °C at 12.5% and 17.5% of salinity and after 4 h. The recovery rate of both normal and carotenoid-accumulating cells in gravity sedimentation experiments was not significantly affected by changing initial dissolved oxygen in the cell-cultured media. Conclusion Considering that gravity sedimentation at the optimum growth temperature for D. salina presented high recovery rates, gravity sedimentation is expected to be a cost-effective method to harvest D. salina from open pond cultivation systems.

Slightly acidic electrolyzed water (SAEW) was developed by Japanese companies over 20 years ago. SAEW has the advantage of potent sterilizing action while being relatively safe. This study evaluated the potential application of SAEW in spatial disinfection. Prior to experiments involving spatial spraying, the ability of SAEW to remove seven type of microorganisms that cause food poisoning was studied in vitro. Results indicated that free chlorine in SAEW, even at a low concentration (30 mg/L), was able to remove Cladosporium cladosporioides, a typical airborne fungus that degrades food, and spores such as Bacillus subtilis, a hardy bacterium. In an experiment involving spatial spraying, 3.43 log10 CFU/100 L of Staphylococcus epidermidis was sprayed in a room-sized space; the same space was then sprayed with SAEW. The number of settling microbes was measured and the sterilizing ability of SAEW was assessed. Results indicated that the concentration of S. epidermidis in the space was completely removed after 20 minutes of SAEW spraying. The above findings indicate that SAEW may be used to remove airborne microorganisms via spatial spraying.

Bacterial inactivation is a crucial aspect of sanitation and hygiene. The effectiveness of slightly acidic electrolyzed water (SAEW) for reduction or removal of Escherichia coli, Pseudomonas aeruginosa and Staphylococcus epidermidis was evaluated. The bactericidal activity of SAEW and sodium hypochlorite (NaOCl) against E. coli and P. aeruginosa were compared through in vitro experiments. The effectiveness of SAEW spray was tested against S. epidermidis. Results showed that SAEW had a more powerful bactericidal activity than NaOCl at the same available chlorine concentrations. For E. coli, SAEW decreased the bacterial counts from 8.4 log10 CFU/mL to less than 3.9 log10 CFU/mL; NaOCl with the same available chlorine of 0.5 mg/L, caused a decrease from 8.4 log10 CFU/mL to 7.1 log10 CFU/mL. For P. aeruginosa, SAEW caused bacterial counts to decrease from 8.5 log10 CFU/mL to less than 4.1 log10 CFU/mL against 8.5 log10 CFU/mL to 6.2 log10 CFU/mL for NaOCl with the same available chlorine of 0.5 mg/L. Spray experiments showed that 10 mg/L of SAEW spray decreased the bacterial counts of S. epidermidis from 3.7 log10 CFU/m3 to 2.8 log10 CFU/m3, with 20 mg/L causing a reduction from 3.8 log10 CFU/m3 to 0 CFU/m3. The overall findings of this study indicate that SAEW may be a promising disinfectant agent either as a solution or spray.

Up-flow column percolation tests are used at laboratory scale to assess the leaching behavior of hazardous substance from contaminated soils in a specific condition as a function of time. Monitoring the quality of these test results inter or within laboratory is crucial, especially if used for Environment-related legal policy or for routine testing purposes. We tested three different sandy loam type soils (Soils I, II and III) to determine the reproducibility (variability inter laboratory) of test results and to evaluate the difference in the test results within laboratory. Up-flow column percolation tests were performed following the procedure described in the ISO/TS 21268-3. This procedure consists of percolating solution (calcium chloride 1 mM) from bottom to top at a flow rate of 12 mL/h through softly compacted soil contained in a column of 5 cm diameter and 30 ± 5 cm height. Eluate samples were collected at liquid-to-solid ratio of 0.1, 0.2, 0.5, 1, 2, 5 and 10 L/kg and analyzed for quantification of the target elements (Cu, As, Se, Cl, Ca, F, Mg, DOC and B in this research). For Soil I, 17 institutions in Japan joined this validation test. The up-flow column experiments were conducted in duplicate, after 48 h of equilibration time and at a flow rate of 12 mL/h. Column percolation test results from Soils II and III were used to evaluate the difference in test results from the experiments conducted in duplicate in a single laboratory, after 16 h of equilibration time and at a flow rate of 36 mL/h. Overall results showed good reproducibility (expressed in terms of the coefficient of variation, CV, calculated by dividing the standard deviation by the mean), as the CV was lower than 30% in more than 90% of the test results associated with Soil I. Moreover, low variability (expressed in terms of difference between the two test results divided by the mean) was observed in the test results related to Soils II and III, with a variability lower than 30% in more than 88% of the cases for Soil II and in more than 96% of the cases for Soil III. We also discussed the possible factors that affect the reproducibility and variability in the test results from the up-flow column percolation tests. The low variability inter and within laboratory obtained in this research indicates that the ISO/TS 21268-3 can be successfully upgraded to a fully validated ISO standard.

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Teleoperated service robots can perform more complex and precise tasks as they combine robot skills and human expertise. Communication between the operator and the robot is essential for remote operation and strongly affects system efficiency. Immersive interfaces are being used to enhance teleoperation experience. However, latency or time delay can impair the performance of the robot operation. Since remote visualization involves transmitting a large amount of video data, the challenge is to decrease communication instability. Then, an efficient teleoperation system must have a suitable operation interface capable of visualizing the remote environment, controlling the robot, and having a fast response time. This work presents the development of a service robot teleoperation system with an immersive mixed reality operation interface where the operator can visualize the real remote environment or a virtual 3D environment representing it. The virtual environment aims to reduce the latency on communication by reducing the amount of information sent over the network and improve user experience. The robot can perform navigation and simple tasks autonomously or change to the teleoperated mode for more complex tasks. The system was developed using ROS, UNITY 3D, and sockets to be exported with ease to different platforms. The experiments suggest that having an immersive operation interface provides improved usability for the operator. The latency appears to improve when using the virtual environment. The user experience seems to benefit from the use of mixed reality techniques; this may lead to the broader use of teleoperated service robot systems.

Dipeptidyl peptidase-4 (DPP-4) is a target to treat type II diabetes mellitus. Therefore, it is important to understand the structural aspects of this enzyme and its interaction with drug candidates. This study involved molecular dynamics simulations, normal mode analysis, binding site detection and analysis of molecular interactions to understand the protein dynamics. We identified some DPP-4 functional motions contributing to the exposure of the binding sites and twist movements revealing how the two enzyme chains are interconnected in their bioactive form, which are defined as chains A (residues 40–767) and B (residues 40–767). By understanding the enzyme structure, its motions and the regions of its binding sites, it will be possible to contribute to the design of new DPP-4 inhibitors as drug candidates to treat diabetes.