Lactic acid fermentation enhances the functional metabolome and antibiofilm potential of edible Scottish seaweeds

Abstract Fermented foods are increasingly in demand for their health-promoting properties and extended shelf life. Seaweeds, which are abundant in minerals, vitamins, and bioactive metabolites, represent an underexplored resource for functional food development. In this study, two edible Scottish brown seaweeds (Alaria esculenta and Laminaria digitata) were subjected to lactic acid fermentation. Microbiological and physicochemical analyses confirmed successful fermentation, which was marked by a pH reduction from 6.0 to 4.5, lactic acid accumulation along with the dominance of lactic acid bacteria, while the incidence of foodborne pathogens remained undetected. Metabolomic profiling by 1H-NMR and LC-High-Resolution Mass Spectrometry (HRMS) revealed specific chemical changes, including the production of oxygenated unsaturated lipids and loliolide, compounds potentially linked to stress and defence responses. Functional analysis highlighted the enrichment of essential unsaturated fatty acid metabolism pathways, particularly in L. digitata. Biological assays demonstrated that fermented seaweed extracts inhibited the biofilm formation of methicillin-resistant Staphylococcus aureus, with enhanced effects observed for fermented L. digitata. Together, these findings demonstrate the feasibility of lactic acid fermentation to valorise edible seaweeds into safe, metabolite-enriched functional foods with potential health benefits.