Abstract
High-temperature Daqu, also called Jiang-flavor Daqu, is the saccharifying and fermenting agent for brewing Jiang-flavor Baijiu. During the spontaneous solid-state fermentation of high-temperature Daqu, variations in temperature and moisture lead to microbial diversity and various metabolites, contributing to the different colors of high-temperature Daqu (customarily referred to as white Daqu, black Daqu, yellow Daqu, and red Daqu in production). We aimed to investigate the differences in microbial communities, physicochemical indices, and potential functions among different high-temperature Daqu with different colors (labeled as QW, QB, QY, and QR) by amplicon sequencing. We found that Kroppenstedtia, Bacillus, and Thermoascus were predominant in all samples; Saccharopolyspora and Thermomyces were predominant in QB and QR; and Unclassfied_O_Eurotiales were predominant in QY. The results on the physicochemical characteristics indicated that compared with other Daqu samples, QW exhibited higher protease activity and lower acidity, whereas QB showed the opposite results. QR had the highest esterification yield, and QY exhibited the highest saccharification but lowest esterification yield. Functional prediction demonstrated that the higher abundances of genes encoding bacterial enzymes of QW and QY were related to the considerably higher abundances of Kroppenstedtia in QW (59%) and QY (87%), respectively. The highest abundance of Thermomyces in QB (80%) contributed to the highest abundance of genes encoding fungal enzymes in QB. This study revealed the microbial and functional dissimilarities of color-based high-temperature starters and helped facilitate the liquor fermentation process.
Highlights
Baijiu (Chinese liquor), one of the six world-famous distilled spirits, is the most widely consumed beverage
The results suggested that the species richness (Chao1) and diversity (Shannon and Simpson) of bacteria were higher than those of fungi in the majority of the samples
The present study focused on the differences among four hightemperature Daqu samples with different colors
Summary
Baijiu (Chinese liquor), one of the six world-famous distilled spirits, is the most widely consumed beverage (over 13 billion liters in 2016). It is produced using a special brewing process and exhibits a distinctive flavor (Liu and Sun, 2018). The Jiang-flavor liquor involves the most complex and distinct brewing process; it is the most widely consumed liquor (Zhao et al, 2016). The Jiang-flavor liquor is manufactured using two key processes: high-temperature Daqu preparation and liquor fermentation (Gan et al, 2019). High-temperature Daqu provides various enzymes and microbial metabolites, which are important sources of the Jiang flavor during liquor fermentation (Wang et al, 2019)
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