Fujia Yang

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.

Cell cryopreservation is essential for food biotechnology and cell-based bioprocessing. However, the widely used cryoprotectant dimethyl sulfoxide (DMSO) shows dose-dependent cytotoxicity, motivating safer alternatives. Here, food-derived antifreeze peptides isolated from Takifugu obscurus skin (TsAFP) were evaluated as primary cryoprotectants using stem cells as a representative cellular model. At 15 mg/mL, TsAFP achieved a 70% replacement of DMSO while maintaining post-thaw cell growth, metabolic activity, adhesion, and multilineage differentiation. TsAFP increased solution viscosity and reduced water activity, effectively inhibiting ice growth and recrystallization. It also adsorbed onto cell membranes to form a protective interfacial layer. Molecular dynamics simulations revealed that TsAFP disrupted water ordering through stable hydrogen-bond interactions. Together, TsAFP provides extracellular and interfacial protection, while low-dose DMSO contributes intracellular protection, resulting in coordinated cryoprotection. TsAFP offers a safer, food-derived strategy to reduce DMSO reliance.

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.

This study aims to explore the cryoprotective mechanisms of food-derived hydrolyzed peptides and develop novel cryoprotectants to enhance the quality of frozen foods. Evynnis japonica scale antifreeze peptides (Ej-AFP) were prepared using enzymatic hydrolysis, which had a 4-fold increase in protection efficiency for surimi compared to traditional cryoprotectants. Furthermore, Ej-AFP was able to control 63.60% of the ice crystals to sizes below 600 μm². Three antifreeze peptide sequences were purified by using ice-affinity techniques and peptidomics. These sequences demonstrated a 21.75% enhancement in antifreeze activity and an increase of 1 °C in thermal hysteresis activity compared to Ej-AFP. Molecular simulation-elucidated ice-binding surface interacts with ice crystals through hydrogen bonds, while the nonice-binding surface disrupts the orderly arrangement of water molecules. This results in a tightly structured hydration layer around the peptide, increasing the curvature of the ice crystal surface and thereby demonstrating significant antifreeze activity in controlling ice crystal growth.