Sweet Fermented Rice microbial community dynamics

As a traditional rice wine, Sweet Fermented Rice (SFR) is widely loved by people for its unique flavor and high nutritional value. However, the changes in physicochemical properties, microbial community composition, and microbial metabolic pathways during the fermentation of sweet fermented rice have not been evaluated, which can lead to unstable quality of SFR. In this study, we analyzed the dynamic changes of physicochemical indicators, microbial community composition, and microbial metabolic pathways in four periods of traditional SFR fermentation. The results showed that in the early stage of SFR fermentation (A0), fermentation had not yet begun; in the middle and late stages of fermentation (A24 and A36), fungi were dominant, among which the dominant genera (Rhizopus and Wickerhamomyces) were the main fungal genera in the whole fermentation process, accompanied by (Parasitella and Mucor), and the saccharification and fermentation of these fungi caused a decrease in pH and an increase in total acid andtotal sugar content. At the end of fermentation (A43) (Wickerhamomyces) was the dominant genus, and (Candida and Cyberlindnera) were also present. At this time, the alcohol content was detected to be 3.5% (v/v). The total acid and total sugar content increased with the fermentation time and the flavor was the best. The results of diversity analysis showed that the diversity of microbial structure composition increased first and then decreased with the fermentation time. Metabolic pathway analysis showed that energy production and conversion, carbohydrate transport, amino acid transport and metabolic pathways were the most active metabolic pathways in the fermentation agent. At the same time, the three major functions of glycosyltransferases (GT), glycoside hydrolases (GH) and carbohydrate binding modules (CBM) in carbohydrate enzyme analysis participated in the entire fermentation process. This study only provides a certain reference for the optimization of physical and chemical properties and the control of microbial community structure during the fermentation of sweet wine.

甜酒酿（Sweet Fermented Rice, SFR）作为一款传统米酒，凭借其独特风味与高营养价值广受大众喜爱。然而，目前尚未针对甜酒酿发酵过程中的理化特性、微生物群落组成及微生物代谢通路变化开展系统评估，这一缺口易导致甜酒酿品质不稳定。本研究针对传统甜酒酿发酵的四个阶段，分析了其理化指标、微生物群落组成及微生物代谢通路的动态变化。研究结果显示，甜酒酿发酵初期（A0阶段）尚未启动发酵；发酵中晚期（A24、A36阶段）以真菌为优势菌群，其中根霉属（Rhizopus）与威克汉姆酵母属（Wickerhamomyces）为贯穿整个发酵过程的主要真菌类群，伴生有寄生酵母属（Parasitella）与毛霉属（Mucor）；此类真菌的糖化与发酵作用会导致pH值下降，总酸与总糖含量升高。发酵末期（A43阶段）的优势菌群为威克汉姆酵母属（Wickerhamomyces），同时存在假丝酵母属（Candida）与赛伯林德纳酵母属（Cyberlindnera）；此时检测到酒精含量为3.5%（体积分数）。总酸与总糖含量随发酵时长推移逐步升高，此时产品风味达到最佳。多样性分析结果表明，微生物群落结构组成的多样性随发酵进程先升高后降低。代谢通路分析结果显示，能量产生与转化、碳水化合物转运、氨基酸转运及代谢通路为发酵过程中最为活跃的代谢通路。同时，碳水化合物酶类分析中的糖基转移酶（glycosyltransferases, GT）、糖苷水解酶（glycoside hydrolases, GH）及碳水化合物结合模块（carbohydrate binding modules, CBM）三大功能类群全程参与了发酵过程。本研究仅为甜酒酿发酵过程中理化特性优化与微生物群落结构调控提供了一定参考依据。