Kelp (Laminaria japonica) is renowned for its rich content of flavor-enhancing amino acids and nucleotides; however, approximately 40% of kelp, including the thin edges and root areas, is discarded during its processing due to its inferior taste. To recycle these kelp byproducts, we have cultivated a functional microbial consortium through continuous enrichment. Analysis via 16S rRNA sequencing has shown that during the three fed-batch fermentation stages of kelp waste, the microbial community was predominantly and consistently composed of three phyla: Halanaerobiaeota, Bacteroidota, and Proteobacteria. At the genus level, Halanaerobium emerged as the dominant player, exhibiting a trend of initial increase followed by a decline throughout the fermentation process. Enzymes such as alginate lyases and both acidic and neutral proteases were found to play crucial roles in the degradation of kelp residues into sauces. Notably, electronic tongue analysis revealed that the fermented kelp sauce demonstrated strong umami characteristics. Furthermore, four novel umami peptides, EIL, STEV, GEEE, and SMEAVEA, from kelp were identified for the first time, with their umami effect largely attributed to strong hydrogen bond interactions with the T1R1–T1R3 umami receptors. In conclusion, this study proposed a sustainable method for kelp by-product utilization, with implications for other seaweed processing.

Phycobiliproteins from the red alga Porphyra umbilicalis are rich precursors of bioactive peptides, but targeted identification of high-potency sequences remains challenging. To address this, we combined an in silico screening pipeline with experimental validation to discover novel antioxidant peptides. Virtual enzymatic hydrolysis generated 908 candidate sequences, which were filtered down to 12 peptides based on molecular weight, toxicity, hydrophilicity, and bioactivity predictions. Molecular docking and molecular dynamics simulations further identified four candidate peptides (FK, FKP, FRS, and RRF) that were computationally predicted to bind stably within the KEAP1 Kelch domain. Chemical assays confirmed that all four synthesized peptides exhibited dose-dependent DPPH and ABTS radical-scavenging activities, along with Fe²⁺-chelating capacity and ferric reducing antioxidant power. In H₂O₂-stimulated Caco-2 cells, peptide pretreatment protected against cellular oxidative stress by restoring endogenous antioxidant enzyme activities, increasing total antioxidant capacity, and reducing lactate dehydrogenase leakage. Among these, RRF displayed the strongest protective efficacy. Overall, this study presents a practical workflow for mining marine-derived peptides and highlights four candidate peptides whose potential as functional food ingredients warrants further validation in actual P. umbilicalis hydrolysates.