Microalgae as an aquaculture feed produced in a short light-path annular column photobioreactor

In this work, four microalgae species ( Chlorella vulgaris, Trachydiscus minutus , Monodopsis sp., and Monoraphidium sp.) were selected and grown in a novel, 30 L short-light path annular-column photobioreactor (AC-PBR). The aim was to test the microalgae growth on a pilot scale and evaluate the potential use as an alternative fish feed in hatcheries based on the content and composition of fatty acids. All microalgae species reached a high biomass density between 3.65 and 5.32 g DW L −1 during a 14-day trial. The highest growth rate of 0.25 ± 0.05 d −1 was calculated for Trachydiscus culture. The highest total content of fatty acids (TFA) was determined for Monodopsis and Trachydiscus biomass as the concentration reached 74.5 ± 6.3 and 72.4 ± 7.6 mg g −1 DW, respectively. These two species contained mostly eicosapentaenoic acid (EPA; C20:5n3), the crucial FA for carnivorous fish whose concentration reached the value of 25.3 ± 0.9% and 31.9 ± 2.0% of TFA for Monodopsis and Trachydiscus , respectively. A high amount of linoleic acid (LA; C18:2n6), another important FA for freshwater aquafeed, was found in Chlorella biomass up to the concentration of 21.9 ± 1.5% of TFA. The present results suggest the feasibility of in-house cultivation of selected microalgae species as a quality live feed source for fish hatcheries.