Abstract
Polymicrobial co-fermentation is among the distinct character of high-temperature Daqu. However, fungal communities in the three types of high-temperature Daqu, namely, white high-temperature Daqu, black high-temperature Daqu, and yellow high-temperature Daqu, are yet to be characterized. In this study, the fungal diversity, taste, and aroma profiles in the three types of high-temperature Daqu were investigated by Illumina MiSeq high-throughput sequencing, electronic tongue, and electronic nose, respectively. Ascomycota and Basidiomycota were detected as the absolute dominant fungal phylum in all types of high-temperature Daqu samples, whereas Thermomyces, Thermoascus, Aspergillus, Rasamsonia, Byssochlamys, and Trichomonascus were identified as the dominant fungal genera. The fungal communities of the three types of high-temperature Daqu differed significantly (p < 0.05), and Thermomyces, Thermoascus, and Monascus could serve as the biomarkers in white high-temperature Daqu, black high-temperature Daqu, and yellow high-temperature Daqu, respectively. The three types of high-temperature Daqu had an extremely significant difference (p < 0.01) in flavor: white high-temperature Daqu was characterized by sourness, bitterness, astringency, richness, methane, alcohols, ketones, nitrogen oxides, and sulfur organic compounds; black high-temperature Daqu was characterized by aftertaste-A, aftertaste-B, methane-aliph, hydrogen, and aromatic compounds; and yellow high-temperature Daqu was characterized by saltiness, umami, methane, alcohols, ketones, nitrogen oxides, and sulfur organic compounds. The fungal communities in the three types of high-temperature Daqu were significantly correlated with taste but not with aroma, and the aroma of high-temperature Daqu was mainly influenced by the dominant fungal genera including Trichomonascus, Aspergillus, Thermoascus, and Thermomyces. The result of the present study enriched and refined our knowledge of high-temperature Daqu, which had positive implications for the development of traditional brewing technique.
Highlights
Chinese Baijiu is a typical Chinese traditional fermented alcoholic beverage and is one of the best known distilled liquors in the world (Xu and Ji, 2011; Huang et al, 2017; Wang et al, 2017)
On the basis of the extraction of metagenomic DNA from high-temperature Daqu (HTD) samples, Illumina Miseq high-throughput sequencing technology was applied, and a dataset including 1,825,410 high-quality reads of the Internal Transcribed Spacer (ITS) ribosomal RNA (rRNA) gene were generated from 30 HTD samples, with an average of 60,847 ± 12,213 ITS rRNA gene reads per sample
A comprehensive analysis of the information on fungal richness and diversity provided by the two diversity indexes depicted that (Supplementary Figure 1), even when the maximum sequencing depth of a single sample was reached, the slope of the sparse curve gradually decreased, tended to be flat but still increased (Supplementary Figure 1A), implying that new fungal species might be found in HTD samples as the sequencing depth increased
Summary
Chinese Baijiu is a typical Chinese traditional fermented alcoholic beverage and is one of the best known distilled liquors in the world (Xu and Ji, 2011; Huang et al, 2017; Wang et al, 2017). This complex solid-state fermentation process is repeated for seven cycles in an open and uncontrolled environment with multimicroorganisms (Li et al, 2016; Du et al, 2019; Liu et al, 2019) These microorganisms have a major impact on fermentation yield and quality, mainly derived from HTD, a saccharifying starter, and raw material used in the brewing process of SFB The exploration of the fungal diversity of HTD could help to comprehensively reveal their brewing microbial resources and enhance product control
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