Changes in the functional and nutritional profiles of heterogeneous agarans and ulvan-bearing seaweeds fermented with Lacticaseibacillus rhamnosus

Fermentation with lactic acid bacteria is a longstanding method that enhances the sensory and functional properties of food products. This study investigated polyphenols, flavonoids, polysaccharides and fatty acid profiles in seaweeds fermented with Lacticaseibacillus rhamnosus. Results showed that fermenting Gracilaria rangiferina, Ulva lactuca, Vertebrata lanosa, and residual V. lanosa increased polysaccharide yields while slightly reducing co-extracted proteins. It facilitated higher yields of polyphenols (≤ 35.5 g/100 g) in specific species with insignificant differences in radical scavenging activity compared to controls (p < 0.05). L. rhamnosus fermentation increased saturated fatty acids, 2.37-44.8%, slightly decreased polyunsaturated fatty acids in V. lanosa and U. lactuca with omega-6/omega-3 ratios of ∼1.6 and 6.7, respectively. In vitro assays using 0.5-500 μg/mL polysaccharides (173-5615 kDa) from seaweeds revealed >90% viability in human colorectal adenocarcinoma cells. These findings evidence the potential of L. rhamnosus in conserving beneficial seaweed metabolites, thus underscoring their prospects as functional foods.