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Commercial koji has been increasingly used in Chinese Baijiu brewing; however, there are only few studies comparing different koji and their relationship with key components of Chinese Baijiu such as ethyl acetate, ethyl lactate, and higher alcohols. Here, we studied six commercially available koji and showed that the microbial communities in the individual koji varied in composition, with Rhizopus, Aspergillus, and Bacillus primarily associated with starch hydrolysis and Saccharomyces mainly associated with alcohol production. In the brewing processes using the six koji, Saccharomyces was undoubtedly the most abundant fungus and Weissella, Bacillus, and Acinetobacter were the predominant bacterial groups. The levels of ethyl acetate, ethyl lactate, and higher alcohols in all brewing processes using the koji exhibited rapid increase in the early stages of fermentation, which stabilized in the later stages, followed by substantial increase after distillation. The results of metagenomic and redundancy analyses of samples taken during the brewing processes indicated that Saccharomyces from the koji was closely related to the production of ethyl acetate, ethyl lactate, and higher alcohols. This study provides a basis for the quality improvement and application of commercial koji.

Luzhou-flavor baijiu (LFB) is brewed by the combined action of various microorganisms, and its flavor is affected by the microbial community and the genes they express, but which genes are the key ones during LFB brewing is less clear. Based on our previous studies the genes ME2 and adhE were identified as key genes, but which role they play was also unknown. In this study functional microorganisms were screened based on the key genes ME2 and adhE, and they were identified to be Rummeliibacillus suwonensis, Clostridium tyrobutyricum and Lactobacillus buchneri. Then simulated fermentation experiments were carried out with the functional microorganisms, and during the fermentation process expression of the key genes and the amounts of the main flavors were detected to analyze the role of the key genes. The results showed that the key gene ME2 was significantly positively correlated with the contents of the main acids, however the key gene adhE and the formation of the main esters in the LFB brewing process was a significant positive correlation. This study verified the two key genes ME2 and adhE complement each other in the LFB brewing process, playing an important role in promoting the formation of flavor substances, and are very beneficial to improve the quality of LFB.

Abstract We developed a Joule heating decomposition (JHD) method, which applied direct current on the SiC for the epitaxial growth of multi-layer graphene (MLG) films on Si-terminated (0001) face of the high doping 4H-SiC substrate. By this JHD method, the growth time for preparing MLG was only several minutes. Raman spectroscopy was employed to study the influence of the temperature caused by the Joule heating on the quality and the uniformity of the sample. Then, other properties, such as the strain, the layer’s number, and the electric characteristics, of the MLG were studied in details. It was found that the quality of the MLG was substantially dependent on the growth temperature (operation current) and the growth time, while the layer’s number was only dependent on the growth temperature but not the growth time. Finally, less-defect and homogeneous MLG (~ 45 layers) with an area of ~ 12 × 5 mm2 could be obtained at a heating temperature of ~ 1470 °C with duration time of 5 min. By using the linear transmission line method, the specific contact resistance of Au and MLG was 5.03 × 10−5 Ω cm2, and the sheet resistance was 52.36 Ω/sq, respectively.

As the main by-product of Chinese strong-flavor liquor, yellow water plays an important role in the formation of flavor components. Yellow water from different fermentation periods (30th day, 45th day, 60th day) was selected to analyze the aroma components by Headspace solid phase micro-extraction Gas Chromatography−Mass Spectrometry, and the microorganism community was evaluated by high-throughput sequencing technology and bioinformatics analysis of DNA. As the fermentation time was prolonged, the main flavor components significantly increased, and the amount of the common microbial population between yellow water and pit mud increased gradually. Among the common microorganisms, Lactobacillus accounted for the largest proportion, at about 56.96%. The microbes in the yellow water mainly belonged to Firmicutes. The abundance of Bacilli (the main bacteria) gradually decreased with time, at 87.60% at the 30th day down to 68.87% at the 60th day, but Clostridia gradually increased from 10.29% to 27.48%. At the genus level, some microbes increased significantly from the 30th day to 60th day, such as Caproiciproducens, which increased from 2.65% to 6.30%, and Sedimentibacter, increasing from 0.47% to 2.49%. RDA analysis indicated that the main aroma components were positively correlated with Clostridia and negatively correlated with Bacilli.