Bio-Heat Is a Key Environmental Driver Shaping the Microbial Community of Medium-Temperature Daqu
Bio-Heat Is a Key Environmental Driver Shaping the Microbial Community of Medium-Temperature Daqu
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DOI：
10.1128/aem.01550-17
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发表时间：
2017-12-01
影响因子：
4.4
通讯作者：
Xu, Zheng-Hong
中科院分区：
文献类型：
--
作者：
Xiao, Chen;Lu, Zhen-Ming;Xu, Zheng-Hong
“大曲”是传统固态发酵工业中常用的糖化和发酵剂（例如，白酒和醋）。不同批次的大曲微生物群落演替和风味形成模式高度相似，但促进大曲微生物生态时间演替的机制尚不清楚。在这里，我们首先相关的时间配置文件的微生物群落演替与环境变量（温度，水分和可滴定酸度）中温大曲（MT-大曲）在整个发酵。温度动态与MT-大曲微生物群在发酵前12 d的快速演替相关（P <0. 05），而12 d后微生物群结构相对稳定。探讨了温度对MT-大曲菌群聚集的影响。在发酵的前4天，大多数细菌分类群和几种真菌分类群的快速繁殖，包括假丝酵母属（Candida）、Wickerhamomyces和未分类的Dipodascaceae和Dipodomycetales物种，显著地将MT-大曲温度提高到55 ° C。随后，从第4天到第12天，MT-大曲中微生物代谢产生的持续生物热（53至56摄氏度）抑制了大多数微生物的生长，而耐热类群，包括芽孢杆菌、未分类链霉菌、魏氏菌属、嗜热放线菌属、嗜热子囊菌属和嗜热真菌属存活或继续生长。此外，温度作为MT-大曲微生物群形成的主要驱动力被验证。通过将MT-大曲置于37 ° C培养箱中降低发酵温度导致MT-大曲微生物群中耐热分类群（包括芽孢杆菌属、嗜热放线菌属和嗜热放线菌属）的相对丰度降低。研究表明，生物热是促进功能性麦曲菌群形成的主要内源性驱动因素。重要意义人类已经掌握了数千年来在淀粉质谷物上培养功能性菌群的大曲制备技术，众所周知，这些微生物的代谢活性是中国白酒风味产生的关键。微生物群落演替和风味形成的模式在批次之间保持高度相似，但对这些模式和微生物种群对特定环境条件的忠诚度的机制见解仍不清楚。研究表明，在发酵的前4d，大曲砖内产生生物热，伴随着微生物的快速繁殖和代谢。然后，持续的生物热可以作为促进MT-大曲微生物群从第4天到第12天形成的主要内源驱动力。耐热微生物的生物热驱动生长可能有助于风味代谢产物的形成。该研究为大曲发酵过程中基于温度的微生物群功能调控提供了有用的信息。
"Daqu" is a saccharifying and fermenting agent commonly used in the traditional solid-state fermentation industry (e.g., baijiu and vinegar). The patterns of microbial community succession and flavor formation are highly similar among batches, yet the mechanisms promoting temporal succession in the Daqu microbial ecology remain unclear. Here, we first correlated temporal profiles of microbial community succession with environmental variables (temperature, moisture, and titratable acidity) in medium temperature Daqu (MT-Daqu) throughout fermentation. Temperature dynamics significantly correlated (P < 0.05) with the quick succession of MT-Daqu microbiota in the first 12 d of fermentation, while the community structure was relatively stable after 12 d. Then, we explored the effect of temperature on the MT-Daqu community assembly. In the first 4 d of fermentation, the rapid propagation of most bacterial taxa and several fungal taxa, including Candida, Wickerhamomyces, and unclassified Dipodascaceae and Saccharomycetales species, significantly increased MT-Daqu temperature to 55 degrees C. Subsequently, sustained bio-heat generated by microbial metabolism (53 to 56 degrees C) within MT-Daqu inhibited the growth of most microbes from day 4 to day 12, while thermotolerant taxa, including Bacillus, unclassified Streptophyta, Weissella, Thermoactinomyces, Thermoascus, and Thermomyces survived or kept on growing. Furthermore, temperature as a major driving force on the shaping of MT-Daqu microbiota was validated. Lowering the fermentation temperature by placing the MT-Daqu in a 37 degrees C incubator resulted in decreased relative abundances of thermotolerant taxa, including Bacillus, Thermoactinomyces, and Thermoascus, in the MT-Daqu microbiota. This study revealed that bio-heat functioned as a primary endogenous driver promoting the formation of functional MT-Daqu microbiota.IMPORTANCE Humans have mastered the Daqu preparation technique of cultivating functional microbiota on starchy grains over thousands of years, and it is well known that the metabolic activity of these microbes is key to the flavor production of Chinese baijiu. The pattern of microbial community succession and flavor formation remains highly similar between batches, yet mechanistic insight into these patterns and into microbial population fidelity to specific environmental conditions remains unclear. Our study revealed that bio-heat was generated within Daqu bricks in the first 4 d of fermentation, concomitant with rapid microbial propagation and metabolism. The sustained bio-heat may then function as a major endogenous driving force promoting the formation of the MT-Daqu microbiota from day 4 to day 12. The bio-heat-driven growth of thermotolerant microorganisms might contribute to the formation of flavor metabolites. This study provides useful information for the temperature-based modulation of microbiota function during the fermentation of Daqu.