Screening Lactic Acid Bacteria in Traditional Sour Porridge and Analysis of Their Antioxidant Activity

To realize the industrial production of pure sour porridge, the traditional sour porridge from Hequ of Shanxi was used as the donor of lactic acid bacteria, which could be used to produce sour porridge under pure culture condition. Lactic acid bacteria were isolated from the sour porridge with CaCO₃-MRS medium, and lactic acid bacteria with strong tolerance were screened through acid tolerance, bile salt tolerance and simulated gastrointestinal tolerance tests. The strains were identified by physiological and biochemical tests, 16S rDNA and pheS gene sequence. The results showed that strains L10, W10 and Y3 with strong tolerance were selected from 68 strains of lactic acid bacteria, the three strains of lactic acid bacteria were identified as Lactiplantibacillus plantarum. At aggregation assay, the self-agglutination rate of L10, W10 and Y3 were 48.86%, 30.14% and 27.63% respectively. Strains L10, W10 and Y3 were able to survive at MRS medium containing 1.0 mmol/L hydrogen peroxide. In free radical scavenging assays, the fermentation supernatant of L10 possessed the highest ability to scavenge the DPPH radical (95.27%), and the hydroxyl radical and superoxide anion scavenging ability of Y3 were the highest, which were 51.26% and 20.16% respectively. However, the DPPH radical scavenging ability of the intact cell suspension of W10 was the highest (27.53%), and the hydroxyl radical scavenging ability of Y3 was 24.83%, which was the highest among them. Therefore, the three strains of lactic acid bacteria screened from traditional sour porridge possessed the potential applications in the industrial production of pure sour porridge.