Abstract:Chlamydomonas reinhardtii, a nutrient-rich microalgae resource, has great potential for development. This study aimed to screen excellent lactic acid bacteria strains suitable for fermenting C. reinhardtii and investigate the effects of fermentation on its bioactive components and functional properties, providing a scientific basis for the development of novel microalgae fermented functional foods. From 19 lactic acid bacteria strains, using DPPH?scavenging rate, ferric reducing antioxidant power,?and acid production ability as indicators, and after verifying compatibility through cross-streaking on plates, single, double, and triple bacteria fermentation systems were constructed to systematically evaluate fermentation characteristics and functional activity changes. The results showed that Lacticaseibacillus paracasei NKY1, Lactiplantibacillus plantarum Y6-7, and L. plantarum JXJA1-6 had good growth (>108CFU/mL) and no antagonistic effect. The composite fermentation was significantly better than single bacteria fermentation: the double bacteria combination (NKY1&Y6-7) had the highest bacterial count (9.6 lg CFU/mL) after 24 hours of fermentation, and the total flavonoid content in the triple bacteria fermentation system reached its peak after 24 hours of fermentation, significantly higher than the unfermented group and other groups. In addition, the DPPH scavenging rate and FRAP value of the composite fermentation liquid were significantly increased by?116.2%and?114.1%, respectively, compared to the unfermented group, and showed strong α-glucosidase inhibitory activity. Correlation analysis revealed that the total flavonoid content was highly positively correlated with antioxidant activity and α-glucosidase inhibitory activity, which were the core functional factors, while the peptide content was significantly negatively correlated with activity indicators. These results indicate that C. reinhardtii is a suitable substrate for the growth of lactic acid bacteria and can significantly enhance its antioxidant and hypoglycemic potential. This study provides new strategies and technical support for the high value-added transformation and functional food development of C. reinhardtii.