Probiotic Characterization of β-Glycosidase Producing Lactobacillus gullinarum and Its Application in the Fermentation of Black Tea Soup

This study aimed to isolate lactic acid bacteria capable of producing β-glucosidase from healthy infant feces and Chinese northeast sauerkraut. Then the strain with the highest β-glucosidase activity was identified for subsequent evaluation of the safety, probiotic characteristics, and potential application in the fermentation of black tea soup. The results indicated one of the β-glucosidase producing lactic acid bacteria FB20, derived from healthy infant feces demonstrated the highest β-glucosidase activity, quantified at 0.58 U/mL, and was classified as Lactobacillus gullinarum. L. gullinarum FB20 had good acid resistance ability, could survive in the simulated gastric fluid (a survival rate of 96.21%±1.40%), an auto-aggregation rate of 38.87%±0.14% at 8 h, co-aggregation rates of 38.82%±1.10% and 53.92%±1.96% with Escherichia coli and Staphylococcus aureus, respectively. It could effectively scavenge DPPH free radicals, ABTS⁺ free radicals, and hydroxyl free radicals, with scavenging rates of 55.67%±3.19%, 98.47%±0.01%, and 57.65%±3.42%, respectively. It could inhibit α-amylase and α-glucosidase, and the inhibition rates were 67.91%±1.24%, and 66.53%±0.34%, separately. After fermenting black tea soup, the eliminating rates of DPPH, ABTS⁺, and hydroxyl radicals in the fermented black tea soup increased significantly by 12.48%, 4.35%, and 10.57% (P<0.05), respectively, and the total phenolic content also increased by 1.07 mg/mL (P<0.05). Electronic nose analysis results showed that the black tea soup fermented by L. gullinarum FB20 significantly reduced organic sulfides compared to the control group. This study provides a certain theoretical basis for the exploration of β-glucosidase-producing strains and the improvement of their application in fermenting tea soup.