Microbial Diversity and Volatile Flavor Compounds in Tibetan Flavor Daqu

Abstract

In this study, the microbial diversity in Tibetan flavor Daqu was analyzed based on single molecule real-time sequencing (SMRT). The volatile flavor compounds in Daqu were detected using the headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS). In addition, the correlation between various microbes and volatile flavor compounds was explored. Our studies indicated that the dominant bacterial genera in Tibetan flavor Daqu were Oceanobacillus, Kroppenstedtia, Virgibacillus, Enterococcus, Pediococcus, Streptomyces, Saccharopolyspora, Leuconostoc, uncultured_bacterium_f_Lachnospiraceae and Lactobacillus. The dominant fungal genera were Wickerhamomyces, Monascus, Aspergillus and Rhizomucor. 101 volatile compounds were detected in the Daqu samples, including alcohols, acids, esters, aldehydes, hydrocarbons, ketones, ethers, aromatics and pyrazines, and 10 key flavor compounds were identified using the relative odor activity value (ROAV). The results of our correlation analysis showed that Enterococcus was mainly associated with the synthesis of aldehydes such as trans-2-octenal, and uncultured_bacterium_f_lachnospiraceae was associated with the synthesis of most aldehydes. This paper has systematically investigated the physicochemical indices, microbial community structure and flavor compounds of Tibetan flavor Daqu, which is helpful in gaining a deeper understanding of the characteristics of Tibetan flavor Daqu.

Keywords: TF Daqu; microbial diversity; physicochemical indices; volatile flavor compounds.

Figure 1

Process diagram for the production of Tibetan flavor Daqu.

Figure 2

Microbial community structure in the samples at the phylum level: (A) Bacterial and (B) fungal community.

Figure 3

Microbial community structure in the samples at the genus level: (A) Bacterial and (B) Fungal community.

Figure 4

Correlation heatmap between the microbial community and 10 key flavor compounds: 1-Octen-3-ol (OCT), phenylethyl alcohol (PA), phenylacetaldehyde (PH), (E)-2-octenal (EOC), nonanal (NON), (E)-2-nonenal (ENO), decanal (DE), methyl laurate (ML), isovaleric acid (IA), andeugenol (EUG).