Isolation, purification and characterization of antioxidant peptides from Spirulina platensis extracts co-fermentation with Thermus thermophilus HB27 and Saccharomyces cerevisiae CH006

Spirulina platensis (S. platensis) is regarded as an ideal source for antioxidant peptides. Microbial fermentation is an effective strategy to increase the utilization of these peptides from S. platensis. This study isolated peptides from the co-fermentation products (STF) of S. platensis extracts with Thermus thermophilus HB27, and Saccharomyces cerevisiae CH006. Compared to the original extracts, amino acid, and protein contents in STF were increased. Using in vitro antioxidant activities guided fractionation by DEAE-52 chromatography, the fraction, STFP-3, were conducted for structure characterization and in vitro zebrafish embryos evaluations. The amino acid composition, LC-MS/MS, circular dichroism, molecular docking analysis revealed that STFP-3 contained 260 peptides and the top ten peptide sequences were identified. Two peptides, Thr-Phe-Arg-Gly-Pro-Pro (TFRGPP) and Phe-Thr-Arg-Pro-Pro (FTRPP) exhibited more stable inhibitory activity against myeloperoxidase (MPO), and the Pro-Pro structures might play an important role. STFP-3 significantly decreased the production of reactive oxygen species (ROS) (P < 0.05) and inhibited the melanin content (P < 0.05) in zebrafish embryos model. These findings demonstrated the potential of using microbial fermentation treatment to produce antioxidant peptides from S. platensis with T. thermophilus and S. cerevisiae.