Functional microorganisms in Baijiu Daqu: Research progress and fortification strategy for application

Abstract

Daqu is a saccharifying and fermenting starter in the production of Chinese Baijiu; its quality directly affects the quality of Baijiu. The production of Daqu is highly environment-dependent, and after long-term natural domestication, it is rich in a wide variety of microorganisms with a stable composition, which provide complex and diverse enzymes and flavor (precursor) substances and microbiota for Jiupei (Fermented grains) fermentation. However, inoculation with a relatively stable microbial community can lead to a certain upper limit or deficiencies of the physicochemical properties (e.g., saccharification capacity, esterification capacity) of the Daqu and affect the functional expression and aroma formation of the Daqu. Targeted improvement of this problem can be proposed by selecting functional microorganisms to fortify the production of Daqu. This review introduced the isolation, screening, identification and functional characteristics of culture-dependent functional microorganisms in Baijiu-brewing, the core functional microbiota community of Daqu, and the related research progress of functional microorganisms fortified Daqu, and summarized the fortifying strategies of functional microorganisms, aiming to further deepen the application of functional microorganisms fortification in Daqu fermentation and provide ideas for the flavor regulation and quality control of Baijiu.

Unveiling the microbiota of sauce-flavor Daqu and its relationships with flavors and color during maturation

“…The fermenting vitalities of Daqu play a crucial role in the production of sauce-flavor baijiu, influencing the initiation of baijiu fermentation ( Wang B. et al, 2018 ; Li H. et al, 2023 ). In this study, we conducted a comprehensive analysis of neutral protease, α-amylase, glucoamylase, and fermentation ability in the three types of Daqu to evaluate their fermenting vitalities.…”

“…The flavor substances in Daqu serve as the precursors to determine the final flavor and characteristics of baijiu ( Li H. et al, 2023 ). A total of 160 different chemicals were detected, and the fluctuations in flavor substances during the maturation of the three types of Daqu are intricate.…”

“…The intricate brewing processes encompass several essential stages, consisting of Daqu production, solid-state fermentation, distillation, storage and aging, and blending ( Jin et al, 2017 ; Niu et al, 2022 ; Yang et al, 2023 ). As the adage goes, “ Daqu is the backbone of baijiu brewing.” emphasizing the crucial role of Daqu —a fermented agent initiating the solid-state fermentation of baijiu by introducing a diverse array of microbes, enzymes, and flavor precursors, ultimately determining the final quality of base liquor ( De Melo et al, 2019 ; Xia et al, 2022 ; Li H. et al, 2023 ; Yang et al, 2024 ).…”

Bioturbation analysis of microbial communities and flavor metabolism in a high-yielding cellulase Bacillus subtilis biofortified Daqu

“…The use of cellulase can significantly improve the utilization rate of raw materials, reduce the fusel oil content and improve the aroma substances in baijiu ( Zhuansun et al, 2022 ). In order to ensure the safety of baijiu, exogenous non-fermenting substances are prohibited from being added to the fermentation process, and functional microorganisms can be used as carriers to enter the fermentation system of fermented grains for functional expression ( Li, Liu, Liu, Hui, & Pan, 2023 ). In addition, Bacillus bacteria are one of the important functional flora in the microecology of baijiu-brewing, which can secrete a variety of enzymes that hydrolyze raw material components, promote the smooth progress of fermentation process and the full use of biomass ( Li, Fernandez, Vederas, & Gänzle, 2023 ; Tang et al, 2023 ; Tong et al, 2022 ).…”

Short-chain carboxylates facilitate the counting of yeasts in Sub-high temperatureDaqu

“…Supplementing antibiotics in culture media can effectively inhibit bacterial growth and circumvent the interference of bacteria 14. Using the classical plate culture method, sixteen pure yeast cultures and various yeast strains with special functions were successfully isolated from STD samples [15][16][17]. However, the number of pure yeast species obtained through classical methods is significantly lower than those identified by high-throughput sequencing.…”