Analysis of microbial diversity and functional differences in different types of high-temperature Daqu

Abstract

Bacterial communities that enrich in high-temperature Daqu are important for the Chinese maotai-flavor liquor brewing process. However, the bacterial communities in three different types of high-temperature Daqu (white Daqu, black Daqu, and yellow Daqu) are still undercharacterized. In this study, the bacterial diversity of three different types of high-temperature Daqu was investigated using Illumina MiSeq high-throughput sequencing. The bacterial community of high-temperature Daqu is mainly composed of thermophilic bacteria, and seven bacterial phyla along with 262 bacterial genera were identified in all 30 high-temperature Daqu samples. Firmicutes, Actinobacteria, Proteobacteria, and Acidobacteria were the dominant bacterial phyla in high-temperature Daqu samples, while Thermoactinomyces, Staphylococcus, Lentibacillus, Bacillus, Kroppenstedtia, Saccharopolyspora, Streptomyces, and Brevibacterium were the dominant bacterial genera. The bacterial community structure of three different types of high-temperature Daqu was significantly different (p < .05). In addition, the results of microbiome phenotype prediction by BugBase and bacterial functional potential prediction using PICRUSt show that bacteria from different types of high-temperature Daqu have similar functions as well as phenotypes, and bacteria in high-temperature Daqu have vigorous metabolism in the transport and decomposition of amino acids and carbohydrates. These results offer a reference for the comprehensive understanding of bacterial diversity of high-temperature Daqu.

Keywords: Chinese Maotai‐flavor liquor; Illumina MiSeq high‐throughput sequencing; bacterial diversity; functional prediction; high‐temperature Daqu.

FIGURE 1

The workflow traditional method for producing HTD (a); three different types of HTD, from left to right, are as follows: black Daqu, yellow Daqu, and white Daqu (b); the barefoot stepping process by female workers (c)

FIGURE 2

Boxplots of α‐diversity indexes (a and b) and relative abundance and bacterial diversity of HTD samples at the level of phylum and genus (c and d). (a) Number of observed species; (b) Shannon index. The whisker caps represent the minimum and maximum values. The box plot middle, upper, and lower lines represent the median value and first and third quartiles, respectively

FIGURE 3

Relative abundance and bacterial diversity of HTD samples at OTU level

FIGURE 4

PCoA score plots based on Bray–Curtis distance (a); dendrogram based on Bray–Curtis distance calculated using Mahalanobis distances as well as MANOVA (b); within‐group variations of the 3 different types of HTD using Bray–Curtis distance (c). Significant difference is represented by *** (p < .001), ** (p < .01), * (p < .05) and ns (p ≥ .05), respectively

FIGURE 5

Identification of discriminant taxa between 3 different types of HTD by LDA of the effect size. Cladogram of the microbiota (a). Significant discriminant taxon nodes of white Daqu, black Daqu, and yellow Daqu are represented by red, green, and blue, respectively, while nondiscriminant taxon nodes are represented by yellow. Branch areas are shaded according to the highest ranked variety for that taxon. The LDA score indicates the level of differentiation among different types of HTD. A threshold value of 2.0 was used as the cutoff level. Horizontal bar chart showing discriminant taxa (b). Significant discriminant taxa of white Daqu, black Daqu, and yellow Daqu are represented by red, green, and blue, respectively

FIGURE 6

Overview of the bacterial COG profile (a), COG functional categories codes are as follows: A = RNA processing and modification; B = chromatin structure and dynamics; C = energy production and conversion; D = cell cycle control, cell division, chromosome partitioning; E = amino acid transport and metabolism; F = nucleotide transport and metabolism; G = carbohydrate transport and metabolism; H = coenzyme transport and metabolism; I = lipid transport and metabolism; J = translation, ribosomal structure, and biogenesis; K = transcription; L = replication, recombination, and repair; M = cell wall/membrane/envelope biogenesis; N = cell motility; O = posttranslational modification, protein turnover, chaperones; P = inorganic ion transport and metabolism; Q = secondary metabolite biosynthesis, transport, and catabolism; R = general function prediction only; S = function unknown; T = signal transduction mechanisms; U = intracellular trafficking, secretion, and vesicular transport; V = defense mechanisms; W = extracellular structures; Y = nuclear structure; Z = cytoskeleton. Comparative analysis of microbiome phenotypic results of HTD samples (b). Significant difference is represented by * (p < .05) and ns (p ≥ .05), respectively