Abstract: The objective of the study was to examine the structure of the microbial community in spontaneous and back-slopping fermented wheat bran in order to provide a foundation for understanding the relationship between microbial community diversity and the quality of fermented wheat bran. Four samples were obtained through spontaneous fermentation for one day (1#) followed by seven cycles of back-slopping fermentation for one day each (3#, 5#, and 7# from the third, fifth and seventh cycles, respectively). Results showed that for the four samples, the Shannon index of fungi was higher than that of bacteria, indicating that the diversity of fungi is richer than that of bacteria; while the Chao 1 index of fungi was lower than that of bacteria, indicating that the relative abundance of fungi is lower than that of bacteria. At the phylum level, the dominant bacteria in fermented wheat bran were Protebacteria and Firmicutes while the dominant fungus was Ascomycota. At the genus level, the dominant bacteria were Lactobacillus and Pediococcus, while the dominant fungi were Aspergillus and Alternaaria. Principal component analysis revealed that the microbial community structures of samples 3#, 5# and 7# were similar to each other but different from that of sample 1#. The heatmap analysis showed that the dominant bacteria in the early fermentation stage were Cronobacter, Pantoea, Enterobacter and Clostridium, while the dominant bacteria in the later fermentation stage were Lactobacillus and Pediococcus; Aspergillus and Alternaria were the dominant fungi throughout the fermentation process. The results of this study indicated that fermentation methods and back-slopping fermentation cycles had significant effects on the microbial community structure and diversity of fermented wheat bran. Back-slopping fermentation promoted the growth of lactic acid bacteria while inhibiting the growth of pathogenic bacteria.

Key words: wheat bran; high-throughput sequencing; spontaneous fermentation; microbial community; back-slopping