Survival of Probiotic Lactobacillus spp. During Kombucha Fermentation

OBJECTIVES: This study will determine if specific probiotics inoculated into unfermented sweetened tea can survive kombucha fermentation in appreciable quantities. METHODS: Growth curves for six probiotic Lactobacillus spp. in MRS broth or sweetened black tea incubated at species-recommended temperature (30°C or 37°C) or 25°C were created. Inoculated (∼9 logCFU/mL) sweet tea was also fermented with kombucha SCOBYs (n = 3), until a pH of 3.0 was reached. Probiotic populations were documented throughout fermentation and storage and were compared to previously constructed growth curves. Model comparison was performed using multiway ANOVA in R studio to decipher significant differences (p ˂ 0.05) between growth media/temperature and between probiotics. RESULTS: Temperature and medium both had significant effects on the probiotic growth rates, and results showed the probiotics survived better in sweetened tea at 25°C than in sweetened tea at recommended incubation temperatures. Differences in pH indicated the probiotics were unable to acidify the tea pre-fermentation. Fermentation lasted on average 8.3 days, and probiotic populations declined significantly with acidification around day 6. Survival was highly heterogeneous across Lactobacillus species, with final populations ranging from > 1.0 to 3.0 logCFU/mL. CONCLUSIONS: Probiotic Lactobacillus spp. are not well suited for a probiotic kombucha beverage. Of the tested probiotics, L. brevis ATCC 14,869 and L. fermentum ATCC 9338 are the best candidates according to the growth curves. Other probiotics, such as Bacillus coagulans, should be further explored before and during fermentation to produce a probiotic kombucha beverage. FUNDING SOURCES: National Institute of Food and Agriculture (USDA).