Characterizing the microbial community of Pixian Doubanjiang and analysing the metabolic pathway of major flavour metabolites

Traditional Pixian Doubanjiang (PXDBJ) has been registered as a protected geographical indication (PGI) condiment by both Chinese and European Commissions because of its preferred unique flavour. This research was devoted to revealing the common microbial community leading to the best possible flavour feature of traditional PXDBJ manufactured according to heritage technology. Cupriavidus, Burkholderia-Caballeronia-Paraburkholderia, Paucibacter, Sphingomonas, Saccharomycetales and Aspergillus were predominant, although the fungal community slightly varied by manufacturer and ripening time. The resulting interaction network of the microbial community was relatively simple because of the stress of extreme ripening environments (high salt and capsaicin enrichment). The correlation between flavour compounds and microbes was determined and demonstrated that Aspergillus, Bacillus and Lactobacillus had a positive impact on some flavour compounds (including, Asp, Leu, β-ionone and 2-acetylpyrrole). The characteristics of metabolic pathway regulation were further explored, and the tentative results indicated that the intensity of corresponding enzymes in the bacterial community influenced the organic acid content, while enzymes in both bacteria and fungi impacted the characteristics of free amino acids and volatile compounds. These results are beneficial for understanding the correlation between flavour and microbial metabolism with unique heritage technology as well as the fermentation mechanism of Pixian Doubanjiang.