Maotai‐flavor liquor is one of the three basic traditional Chinese baijiu and is also the most famous baijiu in the world. Guizhou Maotai baijiu is the representative of Maotai‐flavor liquor, which has a long history of culture and is prepared using unique brewing methods. However, the main flavor of Maotai‐flavor liquor as well as the mechanism by which its aroma is produced is unclear. In this review, the Da‐qu production and fermentation processes for Maotai‐flavor liquor are briefly described along with the flavoring constituents of Maotai‐flavor liquor that have been recently reported. In addition, the volatile compounds and the aroma derived from Maotai‐flavor liquor are discussed. Finally, the microorganisms for the high‐temperature Daqu and fermentation processes of Maotai‐flavor liquor are discussed. Practical Application Maotai is one of the most famous baijiu in China and the most valuable in the market. However, it is unclear what is the key flavor of Maotai and what microbial metabolism is produced. So, if we can figure out the key flavor substances of Maotai baijiu, we can use the various technology to explore the microbes that produce this flavor to understand the mechanism of the production of Maotai. This will not only achieve breakthroughs in academic value, but also bring higher value to Maotai. On this basis, we can brew Maotai baijiu with better quality according to the fermentation mechanism of Maotai.

Chinese traditional liquor, a major type of global distilled spirits, offers a unique flavor system acquired across thousands of years of development. Owing to the various raw brewing materials, types of koji, fermentation vessels, and processes used during liquor production, significant differences can occur in the content of flavor chemical components, such as esters, alcohols, aromatics, ketones, nitrogen compounds, acids, and aldehydes in the resulting liquor. Therefore, the liquor can be characterized on the basis of four basic flavors: sauce-, strong-, light-, and rice-aroma, and eight derivative flavors: feng-, sesame-, chi-, te-, mixed-, laobaigan-, herbal-, and fuyu-aroma. In this review, we describe the production and development process of Chinese traditional liquor in detail; summarize the flavor types, flavor chemical composition characteristics,and research progress related to this liquor;and discuss the influence of trace chemical components on liquor flavor, with the aim of laying a theoretical foundation for stabilizing the quality and increasing the yield of traditional liquor.

Clostridium spp. are important microorganisms that can degrade complex biomasses such as lignocellulose, which is a widespread and renewable natural resource. Co-culturing Clostridium spp. and other microorganisms is considered to be a promising strategy for utilizing renewable feed stocks and has been widely used in biotechnology to produce bio-fuels and bio-solvents. In this review, we summarize recent progress on the Clostridium co-culture system, including system unique advantages, composition, products, and interaction mechanisms. In addition, biochemical regulation and genetic modifications used to improve the Clostridium co-culture system are also summarized. Finally, future prospects for Clostridium co-culture systems are discussed in light of recent progress, challenges, and trends.

The dominant microorganisms in Daqu were analysed using high‐throughput sequencing during fermentation. There were 16 dominant fungal species accounting for 90.8% of the total fungal abundance with Pichia kudriavzevii accounting for 43%. There were 18 dominant bacterial species accounting for 94% of the total bacterial abundance with Lactobacillus representing >50%. The succession pattern of the microbial populations showed that, prior to the top temperature, the microbial population was rich, consisting of Pichia (yeast), Aspergillus, Rhizopus (moulds), Weissella, Pediococcus and Lactobacillus (bacteria). During the top temperature phase, Thermoascus aurantiacus predominated. After this, in the final Daqu, the microflora were mainly yeasts (Pichia, Saccharomycetales) and the bacteria Lactobacillus, Bacillus, Weissella and Pediococcus. These results lay the foundation for further studies on functional microorganisms in the preparation and the mechanism of Daqu formation. © 2018 The Institute of Brewing & Distilling

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