Fermentation-driven modulation of protein, mineral and peptide bioaccessibility in SC-CO2-defatted spirulina during in vitro digestion

Abstract

Supercritical carbon dioxide-defatted-spirulina (SC-D-Sp) produced under the following conditions (25.0 MPa, 50.0 °C, CO₂ flow rate: 16.0 mL min⁻¹, CO₂/EtOH = 90 : 10, 60.0 min) was used as the substrate for fermentation with lactic acid bacteria (LAB) Lactiplantibacillus plantarum (LP) and Lacticaseibacillus casei (LC). After fermentation, the solid and supernatant fractions were subjected to in vitro simulated gastrointestinal digestion. The resulting digesta were then evaluated for protein content, protein bioaccessibility, bioactive peptides (BPs), mineral content and mineral bioaccessibility, and total antioxidant capacity (TAC). Protein concentrations and protein bioaccessibility in digest-supernatants (control, 5% LP, and 5% LC) were significantly higher than those measured in the corresponding digest-solid fractions. The identified peptide sequences were associated with previously reported bioactivities, including potential angiotensin-converting enzyme's (ACE's) inhibitory, antioxidant, antibacterial, hypotensive, antithrombotic, and calcium-binding activities. Mineral (Mg, P, K, Fe, Cu, and Se) bioaccessibility was also significantly higher in the digested supernatants. Notably, the digested supernatants from the 5% LP and 5% LC fermentations showed elevated TAC values. Principal component analysis (PCA) further indicated that the fermented digested supernatants (5% LP and 5% LC) were associated with variables related to bioactive peptides, antioxidant capacity, mineral bioaccessibility, and protein bioaccessibility.