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Microalgae cultures were used for a WW treatment to remediate nutrients while producing biomass and recycling water. In these trials, raceway ponds (RWPs; 1 and 0.5 ha) were located next to a municipal (WW) treatment plant in Mérida, Spain. The ponds were used for continuous, all-year-round microalgae production using WW as a source of nutrients. Neither CO2 nor air was supplied to cultures. The objective was to validate photosynthesis monitoring techniques in large-scale bioreactors. Various in-situ/ex-situ methods based on chlorophyll fluorescence and oxygen evolution measurements were used to follow culture performance. Photosynthesis variables gathered with these techniques were compared to the physiological behavior and growth of cultures. Good photosynthetic activity was indicated by the build-up of dissolved oxygen concentration up to 380% saturation, high photochemical yield (Fv/Fm = 0.62–0.71), and relative electron transport rate rETR between 200 and 450 μmol e− m−2 s−1 at midday, which resulted in biomass productivity of about 15–25 g DW m−2 day−1. The variables represent reliable markers reflecting the physiological status of microalgae cultures. Using waste nutrients, the biomass production cost can be significantly decreased for abundant biomass production in large-scale bioreactors, which can be exploited for agricultural purposes. 5,079 1,731 10,5 SCIE Q1

Since temperature is an important factor affecting microalgal growth, photosynthetic rate and biomass composition, this study has accordingly focused on its effects on biomass yield and nighttime biomass loss, as well as photochemical changes, using Nannochloropsis oceanica as model species, grown in two outdoor 50-L tubular photobioreactors (PBR). In two independent trials, cultures were subjected to a diurnal light:dark cycle, under a constant temperature of 28 degrees C and, on the second trial, at 18 degrees C. Changes in culture performance were assessed by measuring growth, lipid and fatty acid composition of the biomass in both morning and evening. Our results revealed that N. oceanica shows a wide temperature tolerance with relevant nighttime biomass loss, that decreased at lower temperatures, at the expenses of its daily productivity. Fluorescence measurements revealed reversible damage to photosystem II in cells growing in the PBR under optimal thermal conditions, whereas microalgae grown at suboptimal ones exhibited an overall lower photosynthetic activity. Lipids were partially consumed overnight to support cell division and provide maintenance energy. Eicosapentaenoic acid (EPA) catabolism reached a maximum after the dark period, as opposed to their saturated counterparts; whereas lower temperatures led to higher EPA content which reached the maximum in the morning. These findings are relevant for the production of Nannochloropsis at industrial scale. project: "LEPABE-2-ECO-INNOVATION" - North Portugal Regional Operational Program (NORTE 2020), under the Portugal 2020 Partnership Agreement, through the European Regional Development Fund (ERDF) [NORTE-01-0145-FEDER-000005] project: "DINOSSAUR" - ERDF through Programa Operacional Competitividade e Internacionalizacao (COMPETE2020) [PTDC/BBB-EBB/1374/2014-POCI-01-0145-FEDER-016640] Laboratory for Process Engineering, Environment, Biotechnology and Energy -LEPABE -by the FCT/MCTES (PIDDAC) [UIDB/00511/2020] European Cooperation in Science and Technology (COST) Action: European network for algal-bio-products (EUALGAE) [ES1408] Portuguese national funds from the Foundation for Science and Technology (FCT) [SFRH/BD/129952/2017] project: "SABANA"- European Union [727874] info:eu-repo/semantics/publishedVersion [UID/Multi/04326/2019]

Microcystins produced by freshwater cyanobacteria pose serious threats to human health and are a growing problem in drinking water supplies worldwide. Toxin detection and identification in water reservoirs when cyanobacterial density is still low is a key step to predict harmful algal blooms and to allow the safe use of the resource. For this purpose, developing sensitive and rapid methods of analysis is crucial. Adopting a strategy that couples the use of a filter-feeder organism (Unio elongatulus, Pfeiffer 1825 (Bivalvia: Unionidae)) with matrix-assisted laser desorption ionization—time of flight mass spectrometry (MALDI-TOF MS) technology, effective microcystin detection was achieved. The performances of MALDI-TOF MS, high-liquid-performance chromatography with diode array detector (HPLC-DAD) and enzyme-linked immunosorbent assays (ELISA) test were compared. The results obtained in this study suggest that the exploitation of an efficient bio-accumulator organism, coupled with a rapid and sensitive analytical method, can be a very useful strategy in monitoring programs for early and prompt risk management. UCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Básicas::Centro de Investigación en Ciencias del Mar y Limnología (CIMAR)