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In this paper, a systematic methodology is shown for the scaling-up of Nannochloropsis gaditana production for aquaculture uses. First, an adequate culture medium was developed, prepared using fertilizers instead of pure chemicals. Subsequently, the performance of N. gaditana was modelled as a function of average irradiance; this model being validated in continuous culture experiments. The model was used to determine the optimal dilution rate as well as the expected biomass concentration and productivity at optimal conditions. Finally, outdoor experiments were performed to confirm the model's validity and to determine optimal conditions at real production step. | INTRODUCTIONMicroalgae are unicellular organisms that vary in size and shape.They exist in almost all known habitats. Due to their unique biochemical composition, microalgae are exploited for a variety of applications ranging from pharmaceuticals and nutraceuticals to human food and feed, especially for aquaculture (Spolaore, Joannis-Cassan, Duran, & Isambert, 2006). Traditionally, microalgae production in aquaculture represents one of the main problems in the development of a number of processes; this is due to the typically low productivity and poor quality of the resulting biomass along with contamination and high production costs (Muller-Feuga, 2000).Moreover, replacement of fish meal and fish oil by microalgae biomass has been largely reclaimed as alternative to actual sources that are reaching its maximal production capacity, whereas aquaculture demand continuously increase (Lem, Bjorndal & Lappo, 2014). However, the inclusion of microalgae in aquafeed for fish or crustaceans is still at early stage of development, mainly because the availability of, cheap but with enough quality, microalgae biomass is low and optimal strategies to include it into aquafeed is not fully developed.Different species of microalgae have been tested in fish and crustacean aquafeed, mainly for enhancement of immune system rather than as alternative to conventional raw materials (Canavate, 2017).Whatever the final application, industrial microalgae production Regarding the production system, to carry out microalgae production on a large scale it is essential to select the most suitable photobioreactor type. For this, different parameters must be considered depending on the microorganism selected, such as (1) its optimal growth conditions and resistance to variations in environmental conditions, and (2) In this work, we have developed a process for the outdoor production of microalgae as feed for aquaculture. First, we selected the strain and culture medium, optimized using mineral salts instead of pure chemicals. Following this, we optimized the productivity in continuous culture experiments, and modelled the influence of light availability on the growth rate as a prior step to scaling-up the production to outdoor conditions. Finally, the real outdoor photobioreactor performance was validated, evaluating the composition of the produced biomass and its suitabilit...

Omega-3 long-chain polyunsaturated fatty acids (n-3 LC PUFAs) and vitamin D3 are essential components of human nutrition. A regular human diet is highly deficient in n-3 LC PUFAs. Fish like salmon are highly recommended in the human diet as they are a major source of high-value n-3 LC PUFAs and vitamin D3. The levels of these nutrients have been decreasing over the last few years in farmed salmon, whose production urgently needs sustainable sources of these nutrients. The microalga Nannochloropsis gaditana (NG) is known for its naturally high potential for the production of eicosapentaenoic (EPA, 20:5 n-3) fatty acid. A commercial diet for Atlantic salmon was supplemented with 1% and 10% of spray-dried NG grown under controlled conditions for a high EPA content. Salmon were harvested on day 49, following which, boneless and skinless salmon meat was recovered from fish and analyzed for the fatty acid profile, total fat, and vitamin D3. Vitamin D3, EPA, and docosapentaenoic fatty acid (DPA, 22:5 n-3) levels were significantly increased (p < 0.05) by supplementing the basal diet with 10% NG, thus, NG represents a novel, functional, natural ingredient and a sustainable source of n-3 LC-PUFAs that can raise the levels of healthy fats and vitamin D3 in farmed salmon meat.

Municipal wastewater phycoremediation represents a promising circular economy-based process for wastewater reclamation used to recover water and produce biomass. This study aimed to evaluate a pilot-scale phycoremediation system, using the most efficient strain of microalgae for wastewater reclamation in the Atacama Desert. Nitrogen and phosphorus removal, as well as biomass growth, were compared in different microalgae treatments, namely Muriellopsis sp., Scenedesmus almeriensis, Chlamydomonas segnis, Chlorella pyrenoidosa and Chlorella vulgaris. The most efficient treatments, Muriellopsis sp. and S. almeriensis, were scaled up to 20-L bubble column reactors to evaluate nutrient removal and biomass biochemical profile for potential biotechnological application. Finally, Muriellopsis sp. was selected for a pilot-scale phycoremediation experiment (800-L raceway), which removed 84% of nitrogen, 93% of phosphorus and other chemical compounds after 4 days of treatment to meet most of the Chilean standards for irrigation water (NCh. 1333. DS. MOP No. 867/78). Faecal coliforms count was reduced by 99.9%. Furthermore, biomass productivity reached 104.25 mg·L–1·day–1 value with 51% protein, and pigment content of 0.6% carotenoid, with 0.3% lutein. These results indicate the potential of wastewater phycoremediation at an industrial scale for the production of irrigation water and carotenoid using Muriellopsis sp.