Linking Microbial Functional Gene Abundance and Daqu Extracellular Enzyme Activity: Implications for Carbon Metabolism during Fermentation.

Daqu is the starter of Baijiu, it provides the microbes and enzymes necessary for fermentation. Studies have already established carbohydrate metabolism as the primary functional module in Daqu fermentation. The present study investigated the changes in microbial functions and the relationship between carbohydrate metabolism-related functional genes and extracellular enzyme activity during the Daqu fermentation. Amplicon sequencing identified 38 bacterial and 10 fungal phyla in Daqu samples, while shotgun metagenomic sequencing classified and annotated 40.66% of the individual features, of which 40.48% were prokaryotes. KEGG annotation showed that the pathways related to metabolites were less in the early fermentation stage, but higher in the middle and late stages. The functional genes related to pyruvate metabolism, glyoxylate and dicarboxylate metabolism, and propanoate metabolism were relatively high in the early and late stages of fermentation, while that for start and cross metabolism was relatively low. The study also found that amino sugar and nucleoside sugar metabolism were dominant in the middle stage of fermentation. Finally, the correlation network analysis showed that amylase activity positively correlated with many carbon metabolism-related pathways, while liquefaction activity negatively correlated with these pathways. In conclusion, the present study provides a theoretical basis for improving and stabilizing the quality of Daqu.

Effects of environmental factors on the microbial community changes during medium-high temperature Daqu manufacturing.

Environmental factors and microbial interaction influence the changes in microbial community and enzyme profiles during different stages of medium-high temperature Daqu manufacturing. In this study, the specific changes in microbial community and environmental factors at various stages of Daqu production were comprehensively analyzed using a combination of environmental factor analysis and high-throughput sequencing technology. Further, the effects of environmental factors and microbial interaction on microbial succession were investigated via correlation analysis; the enzymes related to saccharification and ethanol fermentation during Daqu production were explored. The study revealed that the whole process of Daqu production was divided into three stages based on temperature. Fungal were active in the early stage, while bacteria were more active in the middle to later stages. Bacillus, Weissella, Thermoactinomyces and Lactobacillus were the main bacterial genera, while Thermoascus, Thermomyces, Kodamaea, and Aspergillus were the dominant fungi. The effects of ambient humidity, CO2. and moisture on the microbial community were significant, and these environmental factors positively correlated with most fungi, but negatively correlated with Thermoactinomyces, Saccharopolyspora, and Acinetobacter. In addition, the enzymes encoded by fungi, related to saccharification and ethanol fermentation, might be consistent with the high abundance of Thermoascus and Thermomyces. Meanwhile, enzymes encoded by bacteria could mainly originate from Weissella.

Comparative Analysis of Physicochemical Properties and Microbial Composition in High-Temperature Daqu With Different Colors.

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.

Application of hyperspectral technology in detection of agricultural products and food: A Review.

Food is the foundation of human survival. With the development and progress of society, people increasingly focus on the problems of food quality and safety, which is closely related to human's health. Thus, the whole industrial chain from farmland to dining table need to be strictly controlled. Traditional detection methods are time-consuming, laborious, and destructive. In recent years, hyperspectral technology has been more and more applied to food safety and quality detection, because the technology can achieve rapid and nondestructive detection of food, and the requirement to experimental condition is low; operability is strong. In this paper, hyperspectral imaging technology was briefly introduced, and its application in agricultural products and food detection in recent years was systematically summarized, and the key points in the research process were deeply discussed. This work lays a solid foundation for the peers to the following in-depth research and application of this technology.

Rapid determination of pit mud moisture content using hyperspectral imaging.

Lack of moisture can lead to the aging of pit mud, excessive moisture will make it difficult to maintain its shape or even collapse. Therefore, a rapid and nondestructive detection technology for moisture in pit mud using hyperspectral imaging was firstly investigated. Modeling efficiency of various processing was compared in visible (400-1,000 nm) and near-infrared (900-1,700 nm) regions, and the optimal model was SNV-SPA-SVM in near-infrared spectroscopy; the R pre 2 and RMSEP of model were .9953 and 0.0029, respectively. Furthermore, the distribution map showed that the moisture in the new cellar was generally lower than that of old, and the moisture distribution of the old pit mud was more even. Moreover, the moisture content of different layers in the same cellar increased from top to bottom. This work provides strong technical support for liquor brewing enterprises to effectively implement online monitoring of pit mud changes and open a new era for the application of hyperspectral imaging technology in the field of liquor solid-state fermentation.

Colorimetric detection of Cr (VI) based on the leaching of gold nanoparticles using a paper-based sensor.

Herein, we have developed a simple, sensitive and paper-based colorimetric sensor for the selective detection of Chromium (Ⅵ) ions (Cr (VI)). Silanization-titanium dioxide modified filter paper (STCP) was used to trap bovine serum albumin capped gold nanoparticles (BSA-Au NPs), leading to the fabrication of BSA-Au NPs decorated membrane (BSA-Au NPs/STCP). The BSA-Au NPs/STCP operated on the principle that BSA-Au NPs anchored on the STCP were gradually etched by Cr (VI) as the leaching process of gold in the presence of hydrobromic acid (HBr) and hence induced a visible color change. Under optimum conditions, the paper-based colorimetric sensor showed clear color change after reaction with Cr (VI) as well as with favorable selectivity to a variety of possible interfering counterparts. The amount-dependent colorimetric response was linearly correlated with the Cr (VI) concentrations ranging from 0.5µM to 50.0µM with a detection limit down to 280nM. Moreover, the developed cost-effective colorimetric sensor has been successfully applied to real environmental samples which demonstrated the potential for field applications.