Microalgae have attracted the interest of industry, academia, and consumers due to their potential as an alternative source of nutrients and bioactive compounds (Oslan et al., 2025). Although the amount and profile of the different nutrients and bioactive compounds can differ according to the microalgae species, in general, they are a good source of proteins and essential amino acids, fat and unsaturated fatty acids, polysaccharides and prebiotic fibers, vitamins (among them provitamin A carotenoids), minerals, and antioxidants (polyphenols, chlorophylls, etc.) which can nutritionally enrich several foods (Sharma et al., 2025; Wang et al., 2023). Among the different microalgae species, one of the most used worldwide is Arthrospira platensis, commonly known as Spirulina, which has been certified as Generally Recognized as Safe (GRAS) (Lafarga et al., 2020).

Spirulina is a good source of marine-derived bioactive peptides (MBPs) (2 to 20 amino acid residues), which are generated through hydrolysis of parent proteins via chemical, enzymatic, microbial, or gastrointestinal digestion (Shahidi & Saeid, 2025). Those marine-derived protein hydrolysates could exhibit a diverse range of bioactivities, encompassing antioxidant, anticancer, antimicrobial, antihypertensive, and antidiabetic properties, making them highly promising for utilization in the food, pharmaceutical, and cosmetic sectors, among others (Tang et al., 2024). Bioactive peptides (BPs) can exert their beneficial effects in two ways: uptake at the apical side of the polarized epithelial cell layer of the upper small intestine, or modulation of metabolic and sensory signaling pathways (Cruz-Casas et al., 2021; Duca et al., 2021; Xu et al., 2019). The transport of BPs involves both passive (paracellular diffusion, transcellular diffusion) and active (transporter-mediated, transcytosis) processes, influenced by peptide characteristics such as hydrophobicity, charge, molecular weight, amino acid sequence, stability, and susceptibility to enzymatic degradation (Q. Xu et al., 2019). Additionally, spirulina protein has presented a well-balanced amino acid profile, riching in essential amino acids and exceeding the reference standard of WHO/FAO/UNU (Ma et al., 2024).

Despite those advantages, the main limitations in the consumption of microalgae by consumer rejection due to their unfavorable organoleptic properties (Migliore et al., 2025). Some promising strategies could be performed to overcome this barrier and retain the high-value-added compounds. At this stage of development, alternative ways to the conventional extraction methods to recover oil and proteins from microalgae are explored. Supercritical carbon dioxide (SC-CO2) has been used as an interesting tool to enhance the oil extraction and separation of valuable compounds from Spirulina (Crampon et al., 2017; Milovanovic et al., 2025). Moreover, beyond oil and essential fatty acids (EFAs) extraction after SC-CO2, it is possible to obtain a remaining cake, which is a great source of protein, bioactive peptides, and essential amino acids (Wang et al., 2023).

In order to obtain bioactive peptides or bioactive compounds from spirulina, several strategies could be used, with enzymatic hydrolysates (EH) being among the most widely applied (Leong & Chang, 2024; Sannasimuthu et al., 2019; Villaró et al., 2023). Spirulina protein hydrolysates have been operated with EH (Alcalase and Flavourzyme) and alkaline extraction after ultrasonication and pre-enzymatic assistance with cellulase, leading to the identification of antioxidant and immunomodulatory properties (Htoo et al., 2024). In another study, the improvement of heat treated spirulina proteins and their EH on osteoporosis under simulated microgravity in mice has been examed, and the spirulina hydrolysate enhances bone health by modulating FoxO/Wnt/β-Catenin signaling pathway and gut microbiota; this study also highlighting the potential of microwave-heated spirulina protein for enhancing food supply and health maintenance in space missions (Zhang et al., 2024). However, compared to EH-based approaches, research focusing on spirulina fermentation to generate the BPs remains relatively limited (Kavak et al., 2025; Spínola et al., 2024).

Fermentation of microalgae, particularly by lactic acid bacteria (LAB), is emerging as a promising strategy to generate the high-value-added compounds (Ricós-Muñoz et al., 2023). Microalgae fermentation to obtain high-value-added compounds with bioactive properties has already been demonstrated (Pérez-Alva et al., 2022). Specifically, the effect of fermentation to enhance the nutritional and bioactive properties of spirulina after using Lactiplantibacillus plantarum ATCC 8014 has been reported (de Marco Castro et al., 2019), with the maximum in the phenolic and C-phycocyanin contents, and total antioxidant capacity (TAC) values were achieved after 36 h of fermentation (de Marco Castro et al., 2019). Similarly, mixed consortia of Bacillus subtilis and L. plantarum for S. platensis fermentation using the random-centroid optimization (RCO) methodology with odor and nutrition assessments were investigated, and over 30 % protein hydrolysis, a 16–19 % increase in polypeptide content, and a 6–19 % rise in essential free amino acids have been achieved at the optimal mixed fermentation condition (Bao et al., 2018).

Building on the promising findings and aiming to combine the green process and microbial fermentation, this study has investigated the LAB fermentation in SC-CO2 defatted spirulina (SC-D-Sp) with Lactiplantibacillus plantarum (LP) and Lactiplantibacillus casei (LC). Then, the protein content, bioactive peptides (BPs), and mineral composition were subsequently characterized in fermentation solids and supernatants, along with the TAC of fermentation supernatants, using LC-TOF-MS/MS, ICP-MS, and spectrophotometric measurements. The overarching objective is to determine whether the application of LAB fermentation in SC-D-Sp can enhance the recovery of valuable high-added-value compounds (i.e., antioxidant bioactive peptides and minerals) and improve functionality as a high-value-added ingredient for food applications.