Unlocking the Potential of Fermented Macroalgae for Plant-Based Foods: From Microbial Bioprocessing to Functional Applications

Growing demand for sustainable plant-based foods has increased interest in marine macroalgae as food raw materials. However, the complex structure of macroalgal biomass and limited nutrient accessibility restrict its direct use, creating a need for processing strategies that improve its nutritional, technological, and sensory properties. This review critically evaluates microbial fermentation as an approach to macroalgal processing, integrating biomass characteristics, pretreatment, starter-culture selection, fermentation conditions, and biotransformation mechanisms. Evidence indicates that fermentation can improve nutrient bioaccessibility, promote the formation or release of bioactive compounds, contribute to product preservation, and reduce characteristic marine flavors and odors, supporting the potential use of fermented macroalgae in beverages, dairy alternatives, and sauces. However, evidence for these effects is not uniform, and some reported probiotic, antioxidant, and health-related benefits remain insufficiently established. Industrial implementation is limited by safety concerns related to potentially toxic elements and high iodine concentrations, particularly in brown algae, as well as challenges involving starter-strain selection, process standardization, scale-up, regulatory requirements, and product quality. Future research should prioritize the optimization of strain–substrate combinations, standardized fermentation protocols, safety assessment, process control, scale-up strategies, and experimental validation of functional effects. This review provides a framework for linking macroalgal substrate characteristics, microbial selection, and processing conditions with potential applications in plant-based foods.