Effect of light stress on lutein production with associated phosphorus removal from a secondary effluent by the autoflocculating microalgae consortium BR-UANL-01.

Microalgae have become promising microorganisms for generating high-value commercial products and removing pollutants in aquatic systems. This research evaluated the impact of sunlight intensity on intracellular pigment generation and phosphorus removal from secondary effluents by autoflocculating microalgae consortium BR-UANL-01 in photobioreactor culture. Microalgae were grown in a secondary effluent from a wastewater treatment plant, using a combination of low and high light conditions (photon irradiance; 44 µmol m-2 s-1 and ≈ 1270 µmol m-2 s-1, respectively) and 16:8 h light:dark and 24:0 h light:dark (subdivided into 18:6 LED:sunlight) photoperiods. The autoflocculant rate by consortium BR-UANL-01 was not affected by light intensity and achieved 98% in both treatments. Microalgae produced significantly more lutein, (2.91 mg g-1) under low light conditions. Phosphate removal by microalgae resulted above 85% from the secondary effluent, due to the fact that phosphorus is directly associated with metabolic and replication processes and the highest antioxidant activity was obtained in ABTS•+ assay by the biomass under low light condition (51.71% µmol ET g-1). In conclusion, the results showed that the autoflocculating microalgae consortium BR-UANL-01 is capable of synthesizing intracellular lutein, which presents antioxidant activity, using secondary effluents as a growth medium, without losing its autoflocculating activity and assimilating phosphorus.

Antitumor activity of Chlorella sorokiniana and Scenedesmus sp. microalgae native of Nuevo León State, México.

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.

Polishing of municipal secondary effluent using native microalgae consortia.

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).