Fermentation of Chlorella vulgaris by Stropharia rugosoannulata: An approach for improved aroma and bioactivity.

Chlorella vulgaris is a nutrient-rich microalga whose broader application is limited by its undesirable aroma characteristics. To improve its sensory quality, commercial C. vulgaris powder was fermented with 20 edible Basidiomycota. Stropharia rugosoannulata was identified as the most effective strain for aroma improvement. Sensory evaluation revealed reduced green and earthy while enhanced fruity notes after submerged fermentation, which were associated with decreased pyrazines and the biosynthesis of ethyl esters, including ethyl 2-methylpropanoate, ethyl butanoate, ethyl 2-methylbutanoate, and ethyl hexanoate. In addition, fermented C. vulgaris exhibited enhanced anti-inflammatory and antioxidant activities in tumor necrosis factor-α (TNF-α)-stimulated vascular endothelial EA.hy926 cells. Peptidomic analysis suggested that these bioactivities are attributed to the formation of fermentation-specific bioactive peptides, along with increased abundance of pre-existing peptides. Further, fermented C. vulgaris showed no increased cytotoxicity in HepG2 cells. Overall, fermentation with S. rugosoannulata effectively improved the aroma and bioactivity of C. vulgaris without compromising cellular safety.