Abstract:This study investigated the effects of Gluconacetobacter xylinus on the number of living Lactic acid bacteria, tolerance of Lactic acid bacteria to the gastrointestinal tract, main nutrients, and antioxidant capacity of a fermented mixed juice, were studied in this paper. The results showed that at 30 ℃, Lactic acid bacteria grew rapidly in the mixed juice. After 24 h fermentation, the number of living bacteria was over 8.50 log CFu/mL. The survival rate of Lactic acid bacteria in the single fermentation group and the co-fermentation group after digestion by simulated gastric juice and simulated intestinal juice were more than 60.00%. The survival rate of the juice fermentation group was improved by the bile salt and in vitro digestion as compared with that of the MRS broth fermentation group. Gluconacetobacter xylinus could enhance the bile salt tolerance of Lactic acid bacteria. The pH of the mixed juice after fermentation decreased to less than 3.90, the contents of glucose, malic acid and Vc all decreased significantly (p < 0.05), whilst the content of lactic acid and the antioxidant activity (oxygen radical absorbance capacity (ORAC) value) increased significantly (p < 0.05). Co-fermentation with Gluconacetobacter xylinus and Lactic acid bacteria significantly reduced the monosaccharide content in the mixed juice, but increased the yield of acetic acid and cellulose (p < 0.05). In summary, Gluconacetobacter xylinus could improve the gastrointestinal tolerance of Lactic acid bacteria to a certain extent, reduce the monosaccharide content of in the mixed fruit juice, and increase the acidity of juice and the content of bacterial cellulose.
