环境因子胁迫下食醋大曲固态发酵过程微生物群落应答机制的研究

Nowadays, increasing attention is likely to be poured to the intricate relationship between the environmental parameters and the microbial dynamics in various ecosystems. From an ecological point of view, traditional spontaneous solid-state fermentation (SSF) of Daqu, is a dynamic process due to the combined activity of varieties of microbial populations, which were linked to consecutive environmental conditions. Various factors, such as temperature, moisture content, pH and acidity, related to one another determine the succession of the different environmental conditions appearing throughout the SSF process. Among these environmental factors, temperature was shown to largely affect the microbial dynamics. In previously research, a medium temperature SSF (MTSSF) process and a low temperature SSF (LTSSF) process of Daqu starters were performed to investigate the influence of environmental factors on microbiota dynamics by Illumina-based high-throughput sequencing, and the results indicated that significantly lower bacterial richness and markedly differences in bacterial communities but highly similarities in fungal communities were exhibited, during MTSSF process comparatively to the LTSSF process. In this project, the inoculation temperature at three different stages during traditional SSF of Daqu used for vinegar brewing were changed as follows: (i) temperature at Liangmei stage was controlled at 35-40℃, (ii) temperature at Chaohuo stage was controlled at 40-45℃, (iii) temperature at Dahuo stage was controlled at 55-60℃. We make use of the metagenome together with this on the metatranscriptome can reveal the structure of microbiota and their contribution in ecosystem functioning, as well as their environment response in metabolic regulation, enzymes synthesis and secretion. This study can provide progress in our knowledge of the role of microbiota in contributing to the quality and safety of final products, and will aid in upgrading the vinegar brewing technology and improving the quality and safety of vinegar products.

微生物与环境之间关系是目前研究一大热点。从生态角度看，大曲固态发酵过程中微生物群落结构演变会受发酵温度、pH、水分等环境因子的影响，因此大曲固态发酵过程是探索微生物群落与环境之间关系的良好研究对象。温度是影响大曲固态发酵微生物群落结构演变重要因素。项目前期通过设置中、低温大曲固态发酵试验发现：中、低温大曲固态发酵细菌群落结构和多样性存在显著性差异。本项目拟分别改变传统食醋大曲固态发酵过程晾霉期温度（温度控制在35-40℃）、潮火期温度（温度控制在40-45℃）、大火期温度（温度控制在55-60℃），运用宏基因组学、宏转录组学等微生物分子生态技术，研究大曲固态发酵过程中功能微生物群落间相互协作关系，并结合代谢组学，从DNA、RNA、代谢水平上阐明环境因子胁迫下大曲固态发酵过程微生物群落应答机制。该项目的开展对明确食醋酿造过程中微生物生态功能及其酿造机理，提高食醋的品质和安全性具有重要意义。

项目的背景及其科学意义：.从生态角度看，大曲固态发酵过程中微生物群落结构演变会受发酵温度、pH、水分等环境因子的影响，因此大曲固态发酵过程是探索微生物群落与环境之间关系的良好研究对象。温度是影响大曲固态发酵微生物群落结构演变重要因素。本项目分别改变传统食醋大曲固态发酵过程晾霉期、潮火期、大火期的温度，运用宏基因组学、宏转录组学等微生物分子生态技术，研究大曲固态发酵过程中功能微生物群落间相互协作关系，并结合代谢组学，从DNA、RNA、代谢水平上阐明环境因子胁迫下大曲固态发酵过程微生物群落应答机制。该项目的开展对明确食醋酿造过程中微生物生态功能及其酿造机理，提高食醋的品质和安全性具有重要意义。.主要研究内容：.（1）不同温度条件下大曲固态发酵过程微生物群落动态演变规律分析；.（2）产糖化酶、淀粉酶、纤维素酶等功能微生物多样性及其相互协作关系解析；.（3）环境因素胁迫下大曲固态发酵过程中微生物群落应答机制研究。.重要结果和关键数据：.（1）基于宏基因组分析增温对食醋大曲固态发酵过程中微生物菌群和酶活的影响：与对照组（MT）批次大曲相比，增温实验组（HT）批次大曲中存在更高丰度的嗜热散囊菌目；大曲发酵过程中主要代谢过程分类为碳水化合物代谢和氨基酸代谢，且主要风味物质——乳酸、乙酸、乙醇的形成与碳水化合物代谢相关。HT批次大曲发酵过程中注释到α-淀粉酶和葡聚糖1,4-α-麦芽糖水解酶的相对丰度高于MT批次大曲，且HT大曲注释到更高丰度降解纤维素的β-葡萄糖苷酶和纤维素1,4-β-纤维二糖苷酶，说明增温发酵可能有助于原料中纤维素的降解而提高原料的利用率。.（2）生物强化对食醋大曲特性和微生物群落的影响：将地衣芽孢杆菌等微生物接种发酵后，强化大曲淀粉酶活性提高了6.35%±0.74%。真菌接种强化组（FI）挥发性物质含量最高，乙醇和异戊醇的含量分别达到46.58±1.36 mg/kg和1.55±0.13 mg/kg。大曲在发酵过程中生物量是先上升然后保持稳定，大火期和成曲期细菌总数显着增加，比上霉期增加近两个数量级。