Sustainable Algae Biorefinery for Agriculture aNd Aquaculture

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In situ monitoring of chlorophyll a fluorescence in Nannochloropsis oceanica cultures to assess photochemical changes and the onset of lipid accumulation during nitrogen deprivation

Publication . Carneiro, Mariana; Chini Zittelli, Graziella; Cicchi, Bernardo; Touloupakis, Eleftherios; Faraloni, Cecilia; Maia, Inês Beatriz; Pereira, Hugo; Santos, Tamára; Malcata, Francisco X.; Otero, Ana; Varela, João; Torzillo, Giuseppe

In situ chlorophyll a fluorescence measurements were applied to monitor changes in the photochemical variables of Nannochloropsis oceanica cultures under nitrogen-deplete and nitrogen-replete (control) conditions. In addition, growth, lipid, fatty acid, and pigment contents were also followed. In the control culture, growth was promoted along with pigment content, electron transport rate (ETR), and polyunsaturated fatty acids, while total lipid content and fatty acid saturation level diminished. Under nitrogen-deplete conditions, the culture showed a higher de-epoxidation state of the xanthophyll cycle pigments. Fast transients revealed a poor processing efficiency for electron transfer beyond Q(A), which was in line with the low ETR due to nitrogen depletion. Lipid content and the de-epoxidation state were the first biochemical variables triggered by the change in nutrient status, which coincided with a 20% drop in the in situ effective quantum yield of PSII (Delta F'/F-m'), and a raise in the V-j measurements. A good correlation was found between the changes in Delta F'/F-m' and lipid content (r = -0.96, p < 0.01). The results confirm the reliability and applicability of in situ fluorescence measurements to monitor lipid induction in N. oceanica.

2021Journal article

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Growth and bioactivity of two chlorophyte (Chlorella and Scenedesmus) strains co-cultured outdoors in two different thin-layer units using municipal wastewater as a nutrient source

Publication . Carneiro, Mariana; Ranglová, Karolína; Lakatos, Gergely Ernő; Câmara Manoel, João Artur; Grivalský, Tomáš; Kozhan, Daniyar Malikuly; Toribio, Ana; Moreno, Joaquín; Otero, Ana; Varela, João; Malcata, F. Xavier; Suárez Estrella, Francisca; Acién-Fernándéz, Francisco Gabriel; Molnár, Zoltán; Ördög, Vince; Masojídek, Jiří

The application of microalgae in wastewater treatment has recently been at the forefront of interest due to the increasing concern about environmental protection and economic sustainability. This work aimed to study two chlorophyte species, Chlorella vulgaris and Scenedesmus acutus, co-cultured outdoors in centrate of municipal wastewater as a nutrient source. Two different thin-layer units were used in these trials & mdash; thin-layer cascade (TLC) and thin-layer raceway pond (TL-RWP), suitable for this purpose due to their high biomass productivity and better culture transparency when using muddy wastewater. The units were operated in batch, and subsequently in semi-continuous growth regime & mdash; and monitored in terms of photosynthetic performance, growth, nutrient removal rate, and bioactivity. The results showed that the co-cultures grew well in the centrate, achieving the maximum biomass densities of 1.3 and 2.1 g DW L-1 in TLC and TL-RWP, respectively, by the end of the batch regime and 1.9 and 2.0 g DW L-1 by the end of the semi-continuous regime. Although TL-RWP grown cultures showed faster growth, the TLC-one revealed better nutrient removal efficiencies batch wise than the culture grown in TL-RWP & mdash; removing up to 48% of total nitrogen and 43% of total phosphorus. Conversely, the latter was more efficient under the semi-continuous regime (54% and 42% consumption of total nitrogen and phosphorus, respectively). In the harvested biomass, an important antimicrobial activity (specifically antifungal) was detected. In this sense, the in-vitro growth of the oomycete Pythium ultimum was inhibited by up to 45% with regard to the control. However, no biostimulating activity was observed. The present findings confirm the possibility of using these two species for biomass production in municipal wastewater centrate using highly productive thin-layer systems. This technology can be a valuable contribution to circular economy since the produced biomass can be re-applied for agricultural purposes.

2021Journal article

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