CHARACTERIZATION OF BIOLOGICALLY ACTIVE MOLECULES OFPHARMACOLOGICAL INTEREST EXTRACTED FROM MICROALGAE BYBIOSUSTAINABLE PROCESSES

Microalgae represent a promising source of high-value secondary metabolites, such as antimicrobial, antioxidant, and immunomodulatory compounds, which are of considerable interest to the pharmaceutical industry. However, conventional extraction technologies—often based on environmentally harmful organic solvents—limit their potential for large-scale industrial exploitation. In this context, the research carried out during my PhD program aimed to develop integrated strategies for the sustainable extraction of microalgal bioactive molecules, prioritizing the use of green solvents such as dimethyl carbonate (DMC), in line with the principles of green chemistry. The study focused on the cultivation of the Micractinium pusillum (CELP1) strain, isolated from agricultural water sources in Sicily (Italy), and its comparison with the model species Chlamydomonas reinhardtii cc-1374. Both strains were evaluated in terms of growth kinetics, biomass productivity, extraction yield, and antimicrobial activity, revealing significant differences in their metabolic composition and bioactivity profiles. In parallel, the industrial strain Chlorella sorokiniana was cultivated under both autotrophic and mixotrophic conditions using agro-industrial by-products as alternative nutrient sources, thereby promoting circular bioeconomy models and reducing cultivation costs. The biomass of Chlorella sorokiniana was then subjected to a controlled alkaline treatment with sodium hydroxide (NaOH) to selectively remove chlorophyll, enhancing the purity and quality of the extracts without compromising the integrity of the bioactive compounds. Extracts from Chlorella sorokiniana were characterized by gas chromatography–mass spectrometry (GC–MS) and tested for antimicrobial activity against selected bacterial strains. The results confirmed the effectiveness of green solvent-based extraction methods in preserving and enhancing the bioactive content of microalgal biomass, achieving a significant improvement in antimicrobial properties compared to conventional methods based on chlorinated solvents.