An industrial-size flat plate glass reactor for mass production of Nannochloropsis sp. (Eustigmatophyceae)

A flat plate (10 cm light-path), vertical reactor made of 10-mm glass plates glued together to form a 500- to 1000-1 unit was developed for outdoor production of Nannochloropsis sp., one of the most promising photoautotrophic producer of eicosapentaenoic acid (20:5ω3, EPA) for aquaculture. The energy inputs required for mixing and cooling the culture were calculated and the harvesting regime yielding the highest areal output of cell mass and EPA was identified. The reactor is practically sealed, facilitating successful maintenance of continuous, monoalgal cultures throughout the year. The optimal cell density fell in the range of 5 to 6 × 10⁸ cells ml^-1, a high cell concentration compared with that reported for other mass production systems of Nannochloropsis. This population density yielded in continuous cultures throughout the year an average of 12 g dry cell mass m^-2 day^-1 or 650 mg EPA m^-2 day^-1, on the basis of the entire illuminated reactor area. An economic appraisal is provided for operating a 2000-1 reactor, sufficient to supply all the algal mass for production of the rotifer quantity required by a Seabream hatchery, producing 8 × 10⁶ fingerlings annually. The production cost at this rather modest scale shows strong sensitivity to the cost of labor.