Bacterial communities and volatile compounds in Doubanjiang, a Chinese traditional red pepper paste

Aim: To identify core bacterial communities and volatile compounds and to investigate their relationships in Doubanjiang, a Chinese traditional red pepper paste. Methods and Results: Two main culture-independent methods, polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) and MiSeq sequencing technique, were used to investigate bacterial composition. Headspace solid-phase microextraction combined with gas chromatography-mass spectrometry (HS-SPME-GC-MS) was used to isolate and identify volatile organic compounds. Partial least squares (PLS) regression and correlation coefficients analyses were used for elucidating the relationship between core bacterial community and volatile compounds. Conclusions: Lactic acid bacteria (LAB) and Enterobacteriaceae family were identified primarily by the PCR-DGGE fingerprinting. Furthermore, the core microbiome (>1% average relative abundance) were indentified by Miseq sequencing technique, which mainly assigned to Proteobacteria, Cyanobacteria and Firmicutes phyla. For volatile profile, a total of 29 volatile compounds were identified by HP-SPME-GC-MS, mainly alcohols, esters, aldehydes, ketones and phenols. PLS regression and Pearson's correlation coefficients analyses revealed highly covariable relationships between volatile compounds and bacterial taxa. Notably, Pseudomonas most highly significantly associated with 3-methyl butanal, 2-methyl butanal, benzeneacetaldehyde and 2-acetylpyrrole (P < 0.001), and significantly correlated with 5-methylfurfural and 5-methyl-2-phenyl-2-hexenal (P < 0.01). Significance and Impact of the Study: Core bacterial communities were identified and the relationship between bacterial taxa and flavour compounds was revealed, these results could be beneficial for improving the quality of Doubanjiang.