Kombucha is a?symbiotic?culture?of?lactic acid bacteria, acetic acid bacteria and yeast. Four strains (HC, HD, HQ and HL) of lactic acid bacteria (LAB) were isolated and purified from kombucha and their biological characteristics were evaluated by morphological and physicochemical identification, acid production, growth performance, and salt, acid and bile salt tolerance. The results showed that all of the LAB strains were identified as Lactobacillus plantarum. The optimal growth temperature for these four strains was 30 ℃, and the strains entered the stationary phase of growth after 14 h. The optimal inoculum amount for HC, HD, HQ and HL was 4%, 4%, 6% and 6%, respectively. All these strains could tolerate salts and had good tolerance to acid and bile salt, and HQ was the best among them.

Kombucha, also known as Haibao, is a traditional acidic tea beverage fermented by a symbiotic culture of lactic acid bacteria, acetic acid bacteria and yeast. Lactic acid bacteria (LAB) were isolated and purified from kombucha and the purified strains were identified. The results showed that a total of 4 LAB strains (XC, XD, XL and XQ) were isolated and they were all identified as Lactobacillus plantarum. These strains entered the stationary growth phase after 14 h. For all four strains, both the pH value and titratable acidity declined during their growth. The optimal inoculum size for XC, XD and XQ was 4%, while that for XL was 6%. The optimal growth temperature for these strains was 30 ℃ and none of them was resistant to salts. All these strains had different tolerance to bile salts and acidity and XQ was the most tolerant among them.

As a common probiotic, lactic acid bacteria must be able to withstand gastric acidity and intestinal bile salts and survive in the human body in large amounts. Nowadays, most studies concerning the mechanism of acid resistance of lactic acid bacteria are focused on the theory of proton pump and alkali production. In addition, the contents of exogenous substances such as glucose, amino acid and fatty acid have a certain effect on its tolerance. The mechanism of inhibition lactic acid bacteria under bile salt stress mainly involves bile salt hydrolase, stress protein and the self-protection ability of its cell membrane. This article reviews the existing literature on the mechanism of acid and bile salt resistance of lactic acid bacteria. The second aim of this review is to explore the factors affecting the acid and bile salt resistance of lactic acid bacteria.

The probiotic effects of lactic acid bacteria (LAB) depend on their tolerance to the human gastro-intestinal tract. The acid and bile salt tolerance of four exopolysaccharide-producing strains of Lactobacillus plantarum was examined by the measurement of optical density at 600 nm (OD600 nm) and the plate colony counting. The results showed that the strain F401④ had higher acid tolerance capacity, and F201⑥ had the highest bile salt tolerance capacity which showed more than 100% survival rate after culture for 4 h in the presence of 0.3 and 0.5 g/100 mL bile salt.