The production, characterization, and antioxidant capacity of the carotenoid fucoxanthin from the marine diatom Odontella aurita were investigated. The results showed that low light and nitrogen-replete culture medium enhanced the biosynthesis of fucoxanthin. The maximum biomass concentration of 6.36 g L⁻¹ and maximum fucoxanthin concentration of 18.47 mg g⁻¹ were obtained in cultures grown in a bubble column photobioreactor (Ø 3.0 cm inner diameter), resulting in a fucoxanthin volumetric productivity of 7.96 mg L⁻¹ day⁻¹. A slight reduction in biomass production was observed in the scaling up of O. aurita culture in a flat plate photobioreactor, yet yielded a comparable fucoxanthin volumetric productivity. A rapid method was developed for extraction and purification of fucoxanthin. The purified fucoxanthin was identified as all-trans-fucoxanthin, which exhibited strong antioxidant properties, with the effective concentration for 50% scavenging (EC₅₀) of 1,1-dihpenyl-2-picrylhydrazyl (DPPH) radical and 2,2′-Azino-bis(3-ethylbenzthiazoline-6-sulfonic acid (ABTS) radical being 0.14 and 0.03 mg mL⁻¹, respectively. Our results suggested that O. aurita can be a natural source of fucoxanthin for human health and nutrition.

A new chrysolaminarin, named CL2, with a molecular mass of 7.75 kDa, was purified from the marine diatom, Odontella aurita, using DEAE-52 cellulose anion-exchange chromatography and Sephadex G-200 gel-filtration chromatography. The monosaccharide and structural analysis revealed that CL2 was a glucan mainly composed of glucose, which was linked by the β-d-(1→3) (main chain) and β-d-(1→6) (side chain) glycosidic bond, demonstrated by infrared spectroscopy (IR) and nuclear magnetic resonance (NMR). The antioxidant activity tests revealed that the CL2 presented stronger hydroxyl radical scavenging activity with increasing concentrations, but less was effective on reducing power analysis and scavenging 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical. The influences of nitrogen concentration and light intensity on chrysolaminarin production of O. aurita were further investigated in a glass column photobioreactor, and a record high chrysolaminarin productivity of 306 mg L⁻¹ day⁻¹ was achieved. In conclusion, the chrysolaminarin CL2 from O. aurita may be explored as a natural antioxidant agent for application in aquaculture, food and pharmaceutical areas.

Nitrous oxide (N₂O) is not only recognized as a potent greenhouse gas, but it is also used in industry as a clean energy source. In this study, different electrode materials of carbon felt and graphite were equipped in the ΔnosZ P. aeruginosa/microbial electrolysis cell (MEC) systems to explore the optimization mechanism for long-term N₂O recovery during incineration leachate treatment. The carbon felt group showed a better performance in N₂O recovery across 45 days of operation. The N₂O conversion efficiency was above 80% and the proportion of N₂O in biogas accounted for 80.6% in the carbon felt group. qRT-PCR analysis was conducted to evaluate the expression of genes involved in denitrification (norB) and electroactivity (phzG, phzM, and phzH) of ΔnosZ P. aeruginosa. The results showed a significant upregulation in the suspended biomass (day 21) and the electron-attached biomass (day 45) from the carbon felt-equipped reactor, which was highly related to the opportunity of biomass exposed to the phenazine derivatives. By the carbon felt optimization in the system, 82.6% of the Pseudomonas genus survived after 45 days of operation. These results indicate that the carbon felt electrode has a more sustainable performance for N₂O recovery in the ΔnosZ P. aeruginosa/MEC system.

Steel rolling oily sludge (SROS) is a highly emulsified, high-viscosity hazardous waste, whose apparent viscosity is governed by its oil–water interfacial structure. To clarify the role of the oil phase, model water-in-oil (W/O) and oil-in-water (O/W) emulsions were prepared using oleic acid and palmitic acid, and their rheological behaviors were systematically investigated via steady-state rheometry, optical and polarized-light microscopy, and quantitative droplet-size analysis. The results revealed that pure oleic acid behaved as a Newtonian fluid, whereas the W/O emulsions exhibited pronounced shear-thinning and yield stress due to the hydrogen-bonding network among water droplets. The O/W emulsions showed nearly Newtonian behavior at low oil content, but their viscosity increased sharply upon phase inversion to W/O. Furthermore, palmitic acid significantly enhanced the viscosity and yield stress of both systems. Droplet-size statistics showed that a moderate amount of palmitic acid minimized droplet size and polydispersity, whereas excess palmitic acid enlarged the droplets. Polarized-light microscopy and macroscopic observations confirmed that this viscosity jump was driven by the precipitation of excess palmitic acid, which formed a rigid crystalline network at room temperature. These findings elucidate the viscosity mechanism of SROS and provide a theoretical basis for improving its flowability and resource utilization.

Following publication of the original article [1], the Authors’ Contributions statement need to be changed.