Screening and tolerance property of an acid-producing Bacillus coagulans.

5 Bacillus strains with large calcium-dissolving circle were isolated from the intestinal contents of free-range chickens, and a strain DPLY-7 with good acid-producing ability was screened by HPLC. The classification and attribution of the strain were determined by means of colony morphology, physiological and biochemical characteristics and specific sequence analysis, and its tolerance property were also studied. The results showed that strain DPLY-7 was identified as Bacillus coagulans. The lowest pH of fermentation broth was 5.04 after incubation at 37°C for 10 h. The contents of lactic acid, acetic acid reached 2.60 mg/ml and 1.24 mg/ml, respectively. The survival rate of strain DPLY-7 was 79.76% at pH 2.5 and 42.86% at bile salt concentration 0.5%, and it could tolerate artificial gastric and intestinal fluid and 85°C water bath. Therefore, it was a probiotic with superior performance.