Isolation and identification of blueberry-derived lactic acid bacteria and their probiotic, antioxidant, and fermentation properties

In this study, high-throughput sequencing was used to analyze the microbial diversity and relative abundance of the blueberry epidermis and found that lactic acid bacteria (LAB) represent a relatively abundant group. Putative LAB strains were isolated and purified from the blueberry epidermis by traditional biological methods. Thirty LAB strains were identified by genotype identification, physiological and biochemical test, and 16S rDNA sequence analysis revealed 100% sequence identity between 8 isolated strains and the representative LAB in the blueberry epidermis. Of the 8 strains, ZYN-0417 (Lactobacillus rhamnosus) and ZYN-0221 (Lactobacillus plantarum) showed strong tolerance in the probiotic test. Under gastric acid conditions with a pH of 2.0, the respective survival rate reached 65.71% and 68.85%. The respective survival rate reached 96.45% and 98.37% in 1.8% bile salt. After incubation in vitro gastrointestinal fluid for 240 min, the respective survival rate reached 91.00% and 86.26%. The antioxidant capacity test showed that the DPPH scavenging rate of ZYN-0417 and ZYN-0221 reached 85.45% and 87.45%, with ABTS free radical scavenging rate of 76.03% and 66.17%, OH scavenging rate of 57.30% and 46.93%, and Fe2+ chelating ability of 46.34% and 43.70%, respectively. Fermentation study showed that ZYN-0417 and ZYN-0221 were capable of strong acid production with respective pH values and total acid content of 3.64 and 3.63, 14.88 mg⋅L-1 and 14.85 mg⋅L-1 after 36 h of fermentation. Moreover, ZYN-0417 and ZYN-0221 showed strong extracellular protease activity (82.99 U⋅mL-1 and 95.17 U⋅mL-1, respectively). Blueberry juice fermentation showed robust growth of ZYN-0417 and ZYN-0221 and the viable bacterial number of LAB reached 13∼14 log CUF⋅mL-1 at the end of fermentation. In summary, blueberry-derived LAB have good probiotic and antioxidant properties, and strong fermentation properties in low acid environments, thus showing the potential of their use for the lactobacillus fermentation of fruit and vegetables.