Coccomyxa onubensis (C. onubensis) is an acidotolerant microalga isolated from Tinto River (Huelva), which contains high levels of metal cations in solution, mainly Fe (II) and (III), and Cu (II). Fe is more bioavailable at low pH, mainly because Fe (II) and Fe (III) are far more soluble, especially Fe (III). For this reason, this study aims to evaluate both physiological and biochemical responses of C. onubensis when subjected to Fe (III)-induced stress. Changes in growth, photosynthetic viability and antioxidant responses to the induced oxidative stress were determined. The results obtained suggest that the addition of moderate Fe (III) levels to C. onubensis cultures results in improved growth and photosynthetic viability. Increases in the intracellular levels of the enzyme superoxide dismutase (SOD) and flavonoids, used as antioxidant response biomarkers, a point at Fe (III)-mediated oxidative stress induction. The apparent decrease in the content of other phenolic molecules and polyunsaturated fatty acids might be understood as a sign of antioxidant molecules' involvement in reactive oxygen species (ROS) scavenging. In conclusion, a noticeable antioxidant capacity displayed by C. onubensis allows the use of moderate Fe (III) levels to trigger the accumulation of valuable antioxidant molecules, allowing the production of cell extracts with potential anti-inflammatory activity.

In the present study, the recovery of valuable molecules of proven anti-inflammatory and antimicrobial activity of the acidophilic microalga Coccomyxa onubensis (C. onubensis) were evaluated using green technologies based on ultrasound-assisted extraction (UAE). Using a factorial design (3 × 2) based on response surface methodology and Pareto charts, two types of ultrasonic equipment (bath and probe) were evaluated to recover valuable compounds, including the major terpenoid of C. onubensis, lutein, and the antimicrobial activity of the microalgal extracts obtained under optimal ultrasound conditions (desirability function) was evaluated versus conventional extraction. Significant differences in lutein recovery were observed between ultrasonic bath and ultrasonic probe and conventional extraction. Furthermore, the antimicrobial activity displayed by C. onubensis UAE-based extracts was greater than that obtained in solvent-based extracts, highlighting the effects of the extracts against pathogens such as Enterococcus hirae and Bacillus subtilis, followed by Staphylococcus aureus and Escherichia coli. In addition, gas chromatography–mass spectrometry was performed to detect valuable anti-inflammatory and antimicrobial biomolecules present in the optimal C. onubensis extracts, which revealed that phytol, sterol-like, terpenoid, and even fatty acid structures could also be responsible for the antibacterial activities of the extracts. Moreover, UAE displayed a positive effect on the recovery of valuable molecules, improving biocidal effects. Our study results facilitate the use of green technology as a good tool in algal bioprocess engineering, improving energy consumption and minimizing environmental impacts and process costs, as well as provide a valuable product for applications in the field of biotechnology.

The efficacy of low-frequency ultrasound pulses in cell disaggregation of Chroococcidiopsis sp. aggregates has been studied as a possible strategy to improve the productivity and operation of the cultures. The modulation of the ultrasound pulses allowed to almost disaggregate most of the cyanobacterial aggregates completely while retaining cellular viability in terms of photosynthetic efficiency. In this study we used a strain isolated from the endolithic habitat of the Atacama Desert, the driest desert in the world due to the extremely scarce rainfall, low level of relative humidity and extremely high incident solar radiation. To survive these conditions and reduce the cell exposure to the incident UV radiation, Chroococcidiopsis sp. grows in the form of aggregates, diminishing the associated photo-oxidative damage. However, this adaptation strategy can reduce the availability of both light and nutrients to the growing cells. This study showed that the low-frequency ultrasound pulses were efficient in disaggregating Chroococcidiopsis sp. aggregates, improving light and nutrient availability to the cells. Our results revealed also that the modulated use of ultrasound pulses resulted in a decreased cell sedimentation velocity which becomes advantageous at large scale. The length of the ultrasound pulses can be optimized to achieve complete disaggregation of the aggregates without affecting cell viability. The preservation of cell viability is considered an advantage for eventual large-scale production as disaggregating of the aggregates can result in more homogeneous cultures with less energy needed to perform mechanical agitation. Additionally, our results indicated an improved growth of cyanobacterium in disaggregated cultures.

Photoautotrophic algal cultivation is challenging due to the shadowing effect produced by an increase in the number of cells; under such circumstances, mixotrophic growth might be an efficient alternative. We grew cultures of the autochthonous acidotolerant microalga Elliptochloris sp. on crude technical glycerin or glucose bubbled with either only air or air containing 2.5 % (v/v) CO₂. We found that CO₂ strongly influenced the production of Elliptochloris sp., as higher growth occurred in mixotrophy with CO₂-enriched air compared to that with only air. Mixotrophy with CO₂-enriched air allowed to reach higher biomass productivities and facilitated an increase in the relative abundance of saturated fatty acids. Nevertheless, mixotrophy with only air resulted in an increase of both saturated and unsaturated fatty acids, but biomass productivities were lower. These results, along with the limited biological contamination facilitated by low pH, suggest that this microalga might be attractive for large-scale production within the circular economy model.

Coccomyxa onubensis (C. onubensis) is an acidotolerant microalga isolated from the extremely acidic Tinto River (Huelva), which contains high levels of metals in solution, mainly Fe and Cu. This makes C. onubensis an adequate candidate to easily cope with high levels of oxidative stress by increasing the levels of certain molecules and enzymes, which helps them elicit an adequate antioxidant biochemical response. Thus, C. onubensis is a promising source of bioactive compounds which exhibit in vitro anti-inflammatory activity, including fatty acids, (poly)phenolic compounds and carotenoids. In this study, the correlations between the antioxidant response and anti-inflammatory activity of cell extracts obtained from Fe (III)-stressed microalgal cultures were analyzed. The results suggested a direct relationship between the antioxidant capacity of the microalgal extracts and Fe (III) concentration in the culture medium. Consequently, the production of some of the target antioxidant molecules, including carotenes, xanthophylls and (poly)phenols, increased. The levels of these molecules increased the most in cell extracts obtained from microalgal cultures at 0.25 mM of Fe (III), which was correlated with a 50 % increase in the anti-inflammatory activity of the microalgal extracts in THP-1 differentiated human macrophages. Fe (III)-modulated oxidative stress allowed us to define culture conditions that can enhance the anti-inflammatory activity of C. onubensis extracts, which are enriched in valuable antioxidant molecules. Overall, this study highlighted the utility of a microalgal species from a highly acidic environment as a novel, natural source of anti-inflammatory agents, based on its ability to cope with the oxidative conditions of its habitat.

Parastrephia quadrangularis (tola) is a native plant of the Chilean Andean Altiplano that is traditionally used for its anti-inflammatory properties. In this study, the aerial parts of the plant were analysed to determine their fatty acid (FA) profile and to identify bioactive compounds using gas chromatography–mass spectrometry (GC–MS). Both conventional extraction methods and Supercritical Fluid Extraction (SFE) were employed, using a 2³ factorial design with centre-point replicates. The variables included temperature (30–60 °C), pressure (15–45 MPa), and ethanol as a cosolvent (0–30% v/v). Extraction kinetics were evaluated using a linear spline model under central conditions (45 °C, 30 MPa, 15% ethanol). Response variables included extraction yield, Total Phenolic Content (TPC), antioxidant activity measured by Trolox Equivalent Antioxidant Capacity (TEAC), and FA composition. A factorial design identified pressure and ethanol concentration as key drivers of phenolic content and antioxidant activity, as supported by confocal autofluorescence microscopy. Multi-response optimisation based on the desirability function was applied to simultaneously maximise all response variables, yielding predicted optimal extraction conditions at 60 °C, 45 MPa, and 30% v/v ethanol for P. quadrangularis. The FA profile highlighted polyunsaturated FAs such as oleic, linoleic, and linolenic acids, as well as saturated FAs including palmitic and lignoceric acids, and short-chain non-volatile FAs. GC–MS analysis revealed metabolites potentially responsible for the plant’s traditionally reported therapeutic effects. Overall, these results highlight ethanol-based SFE as a sustainable strategy for recovering phenolic compounds and antioxidant-related fractions from ancestral medicinal plants.