Cancer cases result in 13% of all deaths worldwide. Unwanted side effects in patients under conventional treatments have led to the search for beneficial alternative therapies. Microalgae synthesize compounds with known in vitro and in vivo biological activity against different tumor cell lines. Therefore, native microalgae from the State of Nuevo Leon, Mexico may become a potential source of antitumor agents. The aim of the present study was to evaluate the in vitro cytotoxic effect of Nuevo Leon regional Chlorella sorokiniana (Chlorellales: Chlorellaceae) and Scenedesmus sp. (Chlorococcales: Scenedesmaceae). Native microalgae crude organic extracts cytotoxicity against murine L5178Y-R lymphoma cell line and normal lymphocyte proliferation were evaluated using the MTT reduction colorimetric assay. Cell death pathway was analyzed by acridine orange and ethidium bromide staining, DNA degradation in 2% agarose gel electrophoresis and caspases activity. Results indicated significant (p < 0.05) 61.89% ± 3.26% and 74.77% ± 1.84% tumor cytotoxicity by C. sorokiniana and Scenedesmus sp. methanol extracts, respectively, at 500 µg/mL, by the mechanism of apoptosis. This study contributes to Mexican microalgae biodiversity knowledge and their potential as antitumor agent sources.

This work evaluates the use of native microalgae consortia for a dual role: polishing treatment of municipal wastewater effluents and microalgae biomass feedstock potential for biodiesel or biofertilizer production. An initial screening was undertaken to test N and P removal from secondary effluents and biomass production by 12 consortia. A subsequent treatment was performed by selected consortia (01 and 12) under three operational conditions: stirring (S), S + 12 h of daily aeration (S + A) and S + A enriched with CO₂ (S + AC). All treatments resulted in compliance with environmental regulations (e.g. Directive 91/271/EEC) and high removal efficiency of nutrients: 64–79% and 80–94% of total N and PO₄³⁻-P respectively. During the experiments it was shown that pH alkalinization due to microalgae growth benefits the chemical removal of ammonia and phosphorus. Moreover, advantages of pH increase could be accomplished by intermittent CO₂ addition which in this research (treatment S + AC) promoted higher yield and lipid concentration. The resulting dry biomass analysis showed a low lipid content (0.5–4.3%) not ideal for biodiesel production. Moreover, the high rate of ash (29.3–53.0%) suggests that biomass could be readily recycled as a biofertilizer due to mineral supply and organic constituents formed by C, N and P (e.g. carbohydrate, protein, and lipids).

Microalgae hold great potential for producing purified high-value products (e.g. pigments and polyunsaturated fatty acids) and represent a source of bioavailable nutrients in aquaculture feeds; however, its production is limited by the high costs of harvesting. Recently, microalgae autoflocculation has been considered a useful solution due to the easy recovery of cell aggregates and natural increase in pH that prevents cell lysis. This work evaluates some cultivation conditions that could contribute to autoflocculation, such as natural pH increase and precipitate formation over the productivity and flocculation of 16 microalgae consortia. Results showed a biomass production of 1.4 to 4.4 dry weight (g L-1) and high flocculation of 81 to ~100%, probably due to Ca3(PO4)2 formation. Moreover, the alkaline pH could have facilitated the assimilation of CO2 and explained the increase of inorganic carbon in the solution obtained. Likewise, results showed a marked descent in electrical conductivity (EC) in solution and high mineral content in the biomass (21.4-35.9%). Finally, this study suggests that the studied culture conditions facilitated microalgae harvest, and the resulting biomass could be a source of bioavailable dietary minerals. Therefore, some of these results might be addressed in future studies with individual microalgae species.

Haematococcus pluvialis is a microalga with significant potential due to its capacity to produce carotenoids with antioxidant and nutraceutical benefits. However, the cost of harvesting this microalga, constituting over 30% of total expenses in large-scale production, is a major concern. Efficient flocculation, aiding in cell separation from the culture medium, is crucial to address this issue. The study contrasted Bold’s Basal Medium (BBM) with Lopez-Chuken & Young nutrient solution (LC-Y). The heightened salt content in LC-Y plays a crucial role in fostering saline stress, which is essential for evaluating H. pluvialis flocculation, biomass yield, and carotenoid production. To assess stability and adaptation in a cultivation medium for H. pluvialis, three consecutive batches were executed in 2-liter photobioreactors, starting with H. pluvialis cysts, adaptation, and increased inoculum. Variables like pH, electrical conductivity, and flocculation percentage were monitored. Moreover, the study found that pH had no noticeable effect on flocculation, but electrical conductivity significantly influenced observed flocculation dynamics in the process. Results revealed that LC-Y nutrient solution consistently outperformed BBM, exhibiting higher yields, flocculation rates, and ash content. Chlorophyll a and carotenoid levels were comparable in both media, whereas BBM excelled in chlorophyll b and oil production. According to the results, LC-Y nutritional solution enhances H. pluvialis flocculation as well as biomass yield, offering notable mineral enrichment and establishing itself as a cost-effective option for carotenoid synthesis. In conclusion, adopting LC-Y nutrient solution for H. pluvialis cultivation can boost carotenoid production and lower costs, thereby benefiting industries.

Microalgae cultivation offers a sustainable approach for nutrient recovery from municipal effluents and the production of valuable biomass, although efficient harvesting remains challenging. This study evaluated the adaptation of the microalgal consortium MC-10 in a sequential batch system through reinoculation of its flocculating fraction to enhance harvesting efficiency and mineral recovery. The consortium was initially cultivated under high ionic stress to promote cell aggregation. Laboratory preadaptation using secondary municipal effluents was then conducted, followed by an outdoor evaluation. In the initial propagation stage, flocculation efficiency reached 98%. Using municipal effluents, flocculation values of 99% were obtained, with a 149% increase in flocculating biomass under laboratory conditions, and 84% flocculation with a 125% increase in biomass production under outdoor conditions, demonstrating the consortium’s stability under environmental fluctuations and its suitability for biomass harvesting. The resulting biomass showed high potential as a biofertilizer due to its mineral content (47% dry weight, DW) and acid solubility (83%), indicating high nutrient bioavailability. Additionally, it contained a total carotenoid concentration of 451 μg/g DW, adding antioxidant value. These findings support the use of microalgae cultivation for the valorization of municipal effluents through the production of easily harvestable biomass with potential for reintegration into agricultural systems.