Functional characterisation of Euglena gracilis following growth medium enrichment

In recent years, microalgae, particularly Euglena gracilis, have been candidates for the food/feed industry thanks to their nutritional and functional properties. However, the inclusion of E. gracilis in the diet of livestock animals is little studied, especially regarding its antioxidant activity. Furthermore, microalgae are known for their variability in nutritional quality and functional properties, mainly due to cultivation conditions. For this reason, the aim of the present work was to investigate the nutritional and functional aspects (total phenolic content TPC, Folin-Ciocalteu assay); antioxidant activity (ABTS and FRAP assays) of E. gracilis, grown in three different media, following chemical extraction (H2O:EtOH) and ex vivo digestion method. The microalgae growth media were characterised as follows: EgM (standard medium); ETX (standard medium + aminoacidic-extract); DOE-ETX (ETX + microelements). The results showed an interesting nutritional profile for all the microalgae analysed, although the values were modulated by media nutrients. Although EgM (6.94 ± 0.25 g/L) was characterised by a significant higher growth yield than ETX (5.75 ± 0.14 g/L) and DOE-ETX (4.72 ± 0.17 g/L), results also confirmed by the paramylon content (4.35 ± 0.13; 3.16 ± 0.08; 2.25 ± 0.05 g/L, respectively) (p < 0.05), it did not show a high functional profile. More specifically, DOE-ETX showed higher values for TPC, ABTS, and FRAP, following chemical extraction, in particular 50 and 75% EtOH and ex vivo digestion. These results confirmed the potential of E. gracilis as a valuable source of functional feed ingredients. Further investigations will be crucial to optimise the formulation of the culture medium to obtain a high yield of algae with improved functional characteristics. HIGHLIGHTS Constant population growth has prompted scientific research to investigate new protein alternatives. Euglena gracilis represents a valid candidate. The type of growth medium influences the nutritional and functional profile (total phenolic content and antioxidant activity) of E. gracilis. The addition of microelements to the E. gracilis medium resulted in a higher phenolic content and more marked antioxidant activity.