Enhancing mineral, protein, and bioactive peptides recovery and selectivity via pulsed electric field (PEF)-assisted fermentation of supercritical carbon dioxide (SC-CO2) defatted spirulina and ultrafiltration

In this study, the supercritical carbon dioxide (SC-CO 2 ) defatted spirulina (SC-D- Sp ) (25.0 MPa, 50.0 °C, 16.0 mL/min, and 60.0 min) was used as a substrate to promote lactic acid bacteria (LAB) growth (5% Lactobacillus plantarum (LP) or 5% Lactobacillus casei (LC)) as the sole carbon source. Moreover, pulsed electric field (PEF) treatment (3 kV/cm, 44 pulses, and 99 kJ/kg) was used to promote LAB fermentation. The fermented solids and supernatants were then collected by centrifugation (1409 g force in 30 minutes), and ultrafiltration (membrane size of 10kDa) was applied to obtain the liquid fraction (< 10kDa and >10kDa). The higher protein content was found in solid matrices compared to the liquid fraction. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) allowed the identification of 7 types of bioactive peptide sequences (antioxidant, antithrombotic, hypolipidemic, anticancer, anti-inflammatory, calcium-binding, and zinc-binding). As for inductively coupled plasma-mass spectrometry (ICP-MS) of mineral determination, the liquid fraction> 10kDa presented the highest values for all the Mg, P, K, Ca, and Fe. Moreover, the liquid fraction >10kDa contained higher total antioxidant capacity (TAC). In conclusion, applying SC-D- Sp via PEF-assisted and ultrafiltration could promote the LAB fermentation, and more bioactive sequences with various activities, various mineral distribution, and higher antioxidant compounds. It could lay the groundwork for future work on how these steps affect the in vitro digestion and the health benefits of the resulting bioactive compounds.