Nutritional improvement of Spirulina (Arthrospira platensis) by-product through simultaneous fermentation with Bacillus subtilis (T2A) & (T3P1), and Lactococcus formosensis (JAL 11)

Spirulina (Arthrospira platensis) by-product of phycocyanin extraction are regarded as exceptional sustainable crude feedstock to generate diverse bioactive products due to their abundant amounts of amino acids, fatty acids, proteins, minerals, and phenolic compounds. Despite its potential, Spirulina by-product exhibit sensory deficiencies and nutritional profiles require improvement to produce desired new products, with raised nutritional properties, extended shelf life, and a significant reduction in the undesirable sensory of Spirulina by-product. Bacillus subtilis (B. subtilis) (T2A), B. subtilis (T3P1), and Lactococcus formosensis (JAL 11), were obtained from the culture collection of the Fish and Environmental Health Laboratory, Department of Fisheries, Faculty of Agriculture, Gadjah Mada University, Indonesia to serve as starter cultures, generating and excreting substantial amounts of extracellular enzymes, particularly proteases, which significantly influence the sensory, nutritional, and hygienic attributes of diverse fermented foods and beverages. The objectives of this study were to improve the sensory characteristics and enhance the nutritional features of Spirulina by-product using simultaneous fermentation with B. subtilis and L. formosensis. Spirulina by product was fermented with B. subtilis and L. formosensis at 30 °C for 2, 4, and 6 days under microanaerobic conditions. Total bacterial count, degree of hydrolysis, sensory evaluation, proximate analysis, amino acid composition, and fatty acid profile of fermented Spirulina (FS) and unfermented Spirulina (UFS) were investigated in this study. Results implied that the simultaneous fermentation affected the total bacterial count, with optimum growth occurring on the fourth day, exceeding 2.9 × 109 CFU/g which markedly enhanced the sensory attributes of Spirulina by-product, including odor, colour, and texture (P < 0.05). A fermentation for 4 days effectively attained the optimum degree of hydrolysis and significantly increased the amount of protein by up to 67.61% dry weight, with a rise of 5.42% after fermentation, as compared with UFS (P < 0.05). Fermentation did not significant effect on the lipid and moisture content. Significant higher concentrations of arginine, glycine, isoleucine, methionine, valine, phenylalanine, proline, and serine were observed in FS as compared with UFS. Fermentation also increased essential fatty acids such as methyl linolelaidate, methyl palmitoleate, methyl linolenate, and methyl cis-4-, 7-, 10, 13-, 16, and 19-docosahexaenoate. Consequently, it concludes that simultaneous fermentation improved the protein content, amino acids and fatty acids profiles, deodorized the off-flavour, and produced better texture. This finding contributes for developing an emerging approach to convert the Spirulina by-product into valuable end-products for food and feed.