Seaweed Fermentation: Advances in Biomass Processing and Bioactive Potential

Seaweeds are sustainable, nutrient-rich resources with potential for use in the development of functional foods. Fermentation represents a powerful biotechnological approach to enhance the nutritional, sensory and bioactive profile of seaweed-based products. This review synthesizes the literature published between 2010 and 2025, addressing recent advances in seaweed pre-treatment technologies, fermentation processes and their integration into diverse food matrices, together with associated health benefits. The diversity of seaweeds applied in fermentation, dominated by brown algae, is examined alongside key pre-treatment strategies, ranging from conventional approaches to emerging technologies including ultrasound, high-pressure processing and assisted fermentation, with emphasis on their impact on fermentability and bioactive recovery. The role of microbial groups is critically discussed in relation to their metabolic contributions and functional outcomes. Overall, fermented seaweed-enriched foods emerge as promising innovations in functional food development, with antioxidant activity being the most consistently reported benefit. Seaweed versatility is evidenced by its incorporation into a wide range of fermented products, including miso, beverages, dairy alternatives and sauces. Key future research directions include optimizing microbial–seaweed interactions, exploring under-investigated pre-treatment technologies such as freezing, and elucidating the mechanisms linking fermentation to heavy metal reduction, with the ultimate goal of improving process control, product quality and consumer acceptance.