Analysis of the mould microbiome and exogenous enzyme production in Moutai-flavor Daqu

Abstract

The objective of this study was to isolate and screen the mould microbiome of five Moutai‐flavor Daqu samples and to characterize and quantify the associated exogenous enzymes. In all, 11 and 18 mould genera were identified in the samples by, respectively, a culture‐dependent method and a culture‐independent high throughput sequencing method. Species of Aspergillus and Rhizopus were the dominant mould genera in the Moutai‐flavor Daqu samples. Analysis of enzyme production showed that Aspergillus versicolor in Daqu ZX01 exhibited the highest neutral proteinase activity (2671.0 ± 73.9 U/g) and Rhizomucor pusillus in Daqu DYT01 exhibited the highest saccharifying amylase production ability (1724.6 ± 11.0 U/g). Copyright © 2017 The Institute of Brewing & Distilling

Effects of aging on the quality of roasted sesame-like flavor Daqu

“…A previous study has shown that the contents of important esters in Baijiu are positively correlated with the numbers of LAB, indicating that a lag in fermentation and a lower ester content during Baijiu production could be caused by a lack of LAB [1]. Previous studies have shown that Staphylococcus is dominated in Daqu, with the potential to form amino acids, biogenic amines, aldehydes, free fatty acids, and esters [3,23]. The number of Staphylococcus bacteria was correlated with the biosynthesis of the main organic acids in Baijiu [24].…”

“…Acetobacter, the prevalent bacteria during Baijiu production, greatly influences the flavor and taste of the final product, because it not only produces acetic acid, but also affords acetoin, a biosynthetic in Baijiu liquor [28]. Acetobacter can also select most of the acid-tolerant microbes owing to the high concentrations of acetic acid it produces [3]. In other words, Acetobacter can affect the microbial flora in the fermentation process of Baijiu, which will eventually affect the quality of the final product.…”

“…Syncephalastrum, first detected in Daqu, has been shown to secrete enzymes, such as amylase, glucosidase and pullulanase, that degrade starch [32]. Rhizomucor is also considered to be a functional microbe, with a high ability to produce saccharifying amylase [3,9]. Therefore, Absidia, Rhizopus, Syncephalastrum, and Rhizomucor all contribute to saccharifying and liquefying activities in Daqu although their activity decreased as aging progressed [3,6].…”

“…Rhizomucor is also considered to be a functional microbe, with a high ability to produce saccharifying amylase [3,9]. Therefore, Absidia, Rhizopus, Syncephalastrum, and Rhizomucor all contribute to saccharifying and liquefying activities in Daqu although their activity decreased as aging progressed [3,6]. This might be due to several factors, such as: The activity of enzymes that degrade starch into sugar is different in these genera; the fluctuation in the number of these microorganisms is inconsistent during the whole aging process; and, in addition to these genera, there are other microorganisms, such as bacteria and yeasts, which exhibit saccharifying and liquefying activities.…”

“…Baijiu, one of the most famous traditional distilled spirits in the world, is produced by the spontaneous solid-state fermentation of a sorghum, wheat, and/or rice mixedculture, a process which mainly involves Daqu manufacture and grain fermentation [1,2]. Daqu, the saccharifying and fermenting agent used for brewing Baijiu, is critical for obtaining the final flavor characteristics of Baijiu [3]. Daqu acts not only as a resource for the brewing process, but also provides important crude enzymes, complex microbial flora, and even aroma precursors that will determine the flavor characteristics of the final liquor product [4].…”