Abstract: The aim of this study was to analyze the main acid-producing microorganisms in mature Qu of Xiaoqu Baijiu, saccharified samples made with it and the Qu-making environment, in order to better control the flavor Xiaoqu Baijiu. High performance liquid chromatography (HPLC) was applied to detect the contents of the main acids in the saccharified samples, and high throughput sequencing was applied to analyze the relative abundance and diversity of bacterial community in the mature Qu, and the traditional isolation, screening and sequencing methods were applied to identify the main acetic acid-producing microorganisms in the saccharified samples and Qu-making environment. The acid production ability of the isolated microorganisms was verified in laboratory-prepared saccharified samples. The results indicated that the main acids in the saccharified samples made withmature Qu of Xiaoqu Baijiu were lactic acid and acetic acid. The formation of lactic acid was correlated with the main genera of Lactobacillus, Weissella and Pediococcus, while the formation of acetic acid was caused by Saccharomycopsis fibuligera isolated from the Qu-making environment and saccharified samples. Acetic acid bacteria were scarcely detected and thus hardly correlated with acetic acid formation in this study. This study is the first to report the acetic acid production ability of S. fibuligera, which provides new insights for research on its role and application in acid formation in Baijiu.

Key words: Baijiu; saccharified samples; high throughput sequencing; Saccharomycopsis fibuligera; acidity detection