Enhancement the antibacterial properties of kefir by adding Lactobacillus fermentum grx08.

Kefir is an acidic-alcoholic fermented milk that can provide probiotic benefits such as intestinal microecological balance regulation, antibacterial activity, and anti-inflammatory activity. In this study, Lactobacillus fermentum grx08 isolated from longevous people was used to further improve the health properties of kefir. L. fermentum grx08 and kefir grains obtained from Xinjiang, China were mixed at ratios of 1:1, 5:1 and 25:1 as starters. The 6 Gram-positive and Gram-negative foodborne pathogens were able to grow in the supernatant of kefir, but not in the supernatant of kefir with L. fermentum grx08. With the increasing of amount of inoculated L. fermentum grx08, the antibacterial activity of the mixed fermented kefir gradually increased. The contents of lactic acid, fumaric acid and malic acid in the mixed fermented milk were significantly increased by adding L. fermentum grx08 (P < 0.05), while the content of acetic acid decreased with the increase of L. fermentum grx08, and the content of citric acid was unaffected. This study suggest that the addition of  L. fermentum grx08 shortened the fermentation time, improved the acidity and retained the quality of fermented milk. Moreover, the antibacterial properties of kefir is enhanced by increasing the production of certain acid.