Abstract: The purpose of this study was to analyze the changes in the bacterial community composition and organic acids in naturally fermented mixed fruits added with different amounts of brown sugar (fruit to sugar ratio of 1:1, 2:1 and 3:1, denoted as A, B and C, respectively) . High performance liquid chromatography (HPLC) was used to determine the change of organic acid contents. Polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) was used to analyze the changes in bacterial community, and the results were analyzed by redundancy analysis (RDA). It was found that the Shannon-Wiener index first decreased and then increased in the fermentation process. Lactic acid, malic acid, citric acid and oxalic acid were the main organic acids during fermentation. A total of 19 specific bands were detected by PCR-DGGE, including 7 strains of lactic acid bacteria, 2 strains of Enterobacter, 1 strain of Enterococcus, 2 strains of Pseudomonas, and 3 strains of unidentified microorganisms. RDA showed that in terms of their decreasing contribution to organic acid production, the bacteria were ranked as follows: Lactobacillus plantarum > uncultured Brevundimonas sp. > Enterobacter xiangfangensis > uncultured Lactococcus sp. for citric acid production; and L. plantarum > L. lactis subsp. > E. xiangfangensis > L. lactis subsp. > uncultured Lactococcus sp. for lactic acid production.

Key words: fermented fruit extract; organic acids; polymerase chain reaction-denaturing gradient gel electrophoresis; redundancy analysis