Tolerance and probiotic characteristics of lactic acid bacteria in traditional fermented raw cheese in northern Xinjiang

Abstract:

[Background] Among dairy productsin northern Xinjiang, raw cheese harbors a variety of microorganisms and is a valuable source of high-quality food-grade microorganisms. However, the rich microbial resources contained therein are facing the risk of being lost. [Objective] To establish the growth curves of 41 strains of lactic acid bacteria isolated from raw cheese and characterize their tolerance to low pH environment and probiotic characteristics. [Methods] Forty-one strains of lactic acid bacteria isolated from raw cheese were cultured with simulated gastric fluid and the media containing 0.3%, 0.5%, and 1.0% bovine bile salt. [Results] Among the 41 strains of lactic acid bacteria, 6 strains (QM-5, QM-27, UM-12, UM-18, NM-11, and NM-14) grew well at pH 2.0, 2.5, 3.0, 3.5, and 4.0. In the medium at pH 2.0, QM-5 strain maintained a survival rate above 50% and the viable count more than 10⁸ CFU/mL. The lactic acid bacteria isolated from raw cheese has strong resistance to acid and bile salt and can survive in the gastrointestinal environment. Furthermore, the 41 strains had inhibitory effects on Escherichia coli, Staphylococcus aureus, and Bacillus subtilis. [Conclusion] Three dominant strains with antibacterial activity and comprehensive tolerance to acid, simulated gastric fluid, and bile salt were screened out.