Study on Quantitative Counting Method of Lactic Acid Bacteria Powder

Objective: On the basis of national standard GB 4789.35-2016, a comparative study was conducted on dilution ratio, diluent components and medium components to investigate the influence on the number of viable bacteria when counting lactic acid bacteria powder. Nine strains of Lactobacillus, six strains of Bifidobacterium, three strains of coccus and one strain of Bacillus coagulans were used as research objects. Methods: The method of dilution plate count was used to count the viable bacteria of different lactic acid bacteria powders. Results: According to research findings, the dilution ratio of the initial lactic acid bacteria powder sample had no significant effect on the final count of viable bacteria, and the ISO dilution had significant effects on the viable count results of some Lactobacillus and Bifidobacterium powders (P<0.05); The counting result of Bifidobacterium powder using TOS agar medium was better than that of national standard medium (P<0.05); The counting result of Bacillus coagulans powder using modified spore counting medium was better than PCA and NA counting culture base. Conclusion: The diluent containing casein peptone could increase the number of viable counts of Bifidobacterium powder when plate counting method was used; TOS agar medium was more conducive to the proliferation and culture of Bifidobacterium; The improved spore counting medium was more conducive to the spore germination and proliferation of Bacillus coagulans.