Exploring the potential of eukaryotic microalgae: a biochemical, bioactive, and metabolomic study

Abstract

Microalgae are unicellular photosynthetic microorganisms whose use dates back to ancient times. They stand out for their ability to accumulate proteins, polyunsaturated fatty acids, pigments, and bioactive compounds with nutritional and industrial potential. This study aimed to explore freshwater eukaryotic microalgae by evaluating their chemical composition, as well as their potential applications in the nutraceutical, bioenergy and pharmaceutical sectors. For this purpose, 26 different species of microalgae were evaluated, of which 12 had their biochemical compositions characterized. The microalgae Pediastrum sp. and Chlorella emersonii presented the most promising macromolecular compositions for industrial feasibility studies, with growth rates higher than the other algae (0.96 and 0.90 d-1) and protein content greater than 60%. Pediastrum sp. also stood out for its higher percentage of polyunsaturated fatty acids and superior antioxidant activity, making it promising as a nutritional source. Regarding antimicrobial activity, the microalga C. emersonii was able to inhibit the Gram-positive bacteria Staphylococcus aureus and Enterococcus faecalis. After fractionation, its antimicrobial potential increased, with fractions B and C showing the ability to inhibit the growth of S. aureus at concentrations of up to 50 µg.mL-1 and S. mutans at up to 25 µg.mL-1. Metabolic analysis of these fractions indicated the significant presence of polyunsaturated fatty acids, likely responsible for the antimicrobial activity, as well as secondary compounds that require further investigation. The anti-obesity activity of the extracts was also observed, with lipid-reducing, anti-inflammatory, and appetite-suppressing potential in the microalgae S. bibraianum and Dictyosphaerium sp. S. bibraianum demonstrated the highest lipid-reducing activity, reducing lipid reserves by up to 50%, while Dictyosphaerium sp. exhibited the greatest appetite-suppressing (70% inhibition) and anti-inflammatory activity (95% inhibition). Metabolomic analysis revealed metabolites such as chlorophyll derivatives and polar lipids associated with these bioactivities. The assays also indicated an absence of cytotoxicity in the extracts. In conclusion, the microalgae C. emersonii, Pediastrum sp., and Dictyosphaerium sp. show promise for nutraceutical and pharmaceutical applications. They may be further explored for future industrial applications, standing out from the other algae evaluated in this study.