Microbial communities succession and flavor substances changes during Pixian broad-bean paste fermentation

Abstract

Pixian broad-bean paste (PXDB) is a traditional Chinese fermented condiment with a distinct flavor. The flavors stems from its strong relationship to local microorganisms. This study analyzed changes in key aroma compounds, organic acids, free amino acids (FAA), and the microbial community during different fermentation stages in order to study the correlation between flavors and microbes. Results indicated that the presence of key aroma compounds and organic acids initially increased, then decreased. Changes in total FAA content were divided into two stages due to the addition of chili pepper, however, both stages displayed an increase in FAA levels as fermentation time increased. High-throughput sequencing was used to study the microbial community and succession. Lactobacillus, Prevotella 9, Ruminococcaceae ucg-014, Lysinibacillus, Enterococcus, Weissella, Escherichia-Shigella, Sphingomonas, Aspergillus, Zygosaccharomyces, Candida, and Pichia presented as the primary microorganism during fermentation process. Simultaneously, it was found that bacteria genera indicated a stronger potential correlation with flavors, versus fungi genera. Escherichia-Shigella, Leuconostoc, Acetobacter, Chromohalobacter, Candida, Mortierella, Plectosphaerella, Podoscypha, and Podospora displayed a significant correlation with flavors (isoamyl alcohol, 2,5-dimethylpyrazine, phenethyl alcohol, 2,3,5,6-tetramethylpyrazine, citric acid, serine, asparagine, glutamate, etc.). This study provides an improved understanding on formation mechanisms of flavors, and guidance for screening PXDB fermentation strains.