Chaetomorpha linum Extract as a Source of Antimicrobial Compounds: A Circular Bioeconomy Approach

The circular bioeconomy is currently a promising model for repurposing natural sources; these sources include plants due to their abundance of bioactive compounds. This study evaluated the antimicrobial properties of a <i>Chaetomorpha linum</i> extract. <i>Chaetomorpha linum</i> is an invasive macroalga from the Orbetello Lagoon (Tuscany, Italy), which grows in nutrient-rich environments and has been forming extended mats since 2005. The biomass is mechanically harvested and treated as waste, consuming considerable manpower and financial resources. As a potential way to increase the value of such waste, this study found that <i>C. linum</i> extract (CLE) is a source of antimicrobial compounds. The phytochemical characterization of the extract revealed the predominant presence of palmitic acid, a fatty acid with known antimicrobial activity. Based on such findings, four bacterial species of high clinical relevance (<i>Enterococcus faecalis</i>, <i>Staphylococcus aureus</i>, <i>Pseudomonas aeruginosa</i>, and <i>Escherichia coli</i>) were tested, revealing a notable antibacterial activity of the extract on <i>Enterococcus faecalis</i> (MIC, 32 μg/mL). Computational analyses identified a potential <i>Enterococcus faecalis</i> molecular target for palmitic acid, offering molecular insights on the interaction. This study presents a comprehensive in vitro and in silico approach for drug and target discovery studies by repurposing <i>C. linum</i> as a source of antimicrobial bioactive compounds.