Mixotrophy in Marine Microalgae to Enhance Their Bioactivity

Photosynthetic microorganisms, such as microalgae, are remarkable for their ability to harness sunlight, fix carbon dioxide, and produce a variety of bioactive compounds. These organisms are pivotal in climate mitigation strategies as they can absorb carbon dioxide while generating valuable biomolecules. Among the diverse cultivation approaches, mixotrophic growth combines light energy with both inorganic and organic carbon sources, offering a unique strategy to enhance biomass production and metabolic diversity in microalgae. Here, microalgal species such as Nannochloropsis granulata, Phaeodactylum tricornutum, and Chlorella sp. were investigated for their potential applications under different cultivation methods, including phototrophy and mixotrophy. Mixotrophic conditions significantly improved biomass production across all tested species. Among these, Phaeodactylum tricornutum, a marine diatom, emerged as a promising candidate for bioactive compound production, exhibiting higher antiproliferative activity against human melanoma cells and antibacterial effects against Staphylococcus aureus. Importantly, Chlorella sp. was also found to possess antibacterial activity against Staphylococcus aureus, broadening its potential applications. Additionally, metabolomics analysis was performed on Chlorella sp. and Phaeodactylum tricornutum to identify the compounds responsible for the observed bioactivity. This study highlights the value of mixotrophic cultivation in enhancing the productivity and bioactivity of microalgae, positioning them as versatile organisms for sustainable biotechnological applications.