Fermentation of Chlorella vulgaris , a microalga used in human nutrition, by 89 strains of lactic acid bacteria

Chlorella vulgaris, an edible microalga with significant food potential, is highly prone to spoilage post harvested. Lactic acid bacteria (LAB) fermentation can help preserve it. This study screened 89 LAB strains from 10 species for their ability to grow and acidify a C. vulgaris suspension (50 g/L) and metabolize eight carbohydrates. Results revealed that 72% of strains effectively acidified the suspension, with no link between carbohydrate metabolism and microalgae fermentation. Three top-performing strains were selected and tested with varying glucose and yeast extract levels to optimize acidification: Lactococcus lactis (CIRM-BIA2469), Lactiplantibacillus plantarum (CIRM-BIA2211), and Lactiplantibacillus pentosus (CIRM-BIA2178). Adding 2 g/L glucose optimized acidification lowering pH 4.5 (compared to pH 5 without glucose). LAB fermentation also inhibited Bacillus subtilis, a common contaminant, even at high initial concentrations (6 log10 CFU/mL). This study highlights the undeniable benefits of using lactic fermentation to improve the stability and safety of C. vulgaris in food applications.