Biological Activities of Lactic Acid Bacteria Isolated from Chinese Traditional Cheese and the Application in Antioxidant Foods

Lactic acid bacteria (LAB) are known for their health benefits, which are isolated frequently from various fermented foods. This study aimed to evaluate the safety, metabolite production, antioxidant, and antibacterial activity of LAB isolated from Chinese traditional cheese and their application in fermented dairy products. According to 16S rRNA sequence analysis, seven LAB strains were identified as <i>Lactococcus lactis</i> W3A and W3C, <i>Streptococcus lutetiensis</i> W3B, <i>Enterococcus durans</i> W3D, <i>Leuconostoc mesenteroides</i> W3E, <i>Enterococcus lactis</i> W3F, and <i>Leuconostoc lactis</i> W3J, respectively. Hemolysis and antibiotic sensitivity tests showed that all strains were safe for consumers. Meanwhile, all strains showed a good ability to produce exopolysaccharide (330.57-1097.10 mg L^-1) and organic acid (31.83-65.43 g L^-1). The antioxidant assay indicated that seven LAB strains could effectively scavenge DPPH (37.72-53.13%), ABTS⁺ (95.86-98.67%), ·OH (86.06-95.26%), ·O₂^- (11.88-31.30%) free radicals, and chelate ferrous ion (23.98-54.70%) and could reduce ferric ions (35.56-273.14 μmol L^-1). In addition, they also displayed different antibacterial activity (10-30 mm inhibition zone) against all 13 foodborne pathogenic bacteria. Finally, the two best strains (<i>Leu. lactis</i> W3J and <i>E. lactis</i> W3F) were selected with PCA and EW-TOPSIS methods and used to ferment goat milk. Fermented samples provided a stronger antioxidant ability than the unfermented goat milk. The results suggested that these two LAB strains had potential applications in antioxidant foods.