Abstract: [Objective] The aim of the present study was to characterize the succession of fungal community structure of traditional koumiss from Inner Mongolia at different fermentation stages. [Method] Traditional fermentation methods were used to prepare koumiss using the fresh mare′s milk collected from Xianghuang Banner, Xilin Gol League, Inner Mongolia, as the raw material. The traditional koumiss samples were collected at 0, 12, 24, 36, 48 and 96 h of fermentation, and their pH values were measured. Subsequently, high-throughput sequencing technology targeting on the fungal ribosomal DNA internal transcribed spacer （rDNA-ITS） sequence was used to characterize the changes of fungal community structure at different fermentation stages. [Result] The Chao1 index and Shannon-Wiener′s diversity index analysis demonstrated that in the early stage of fermentation （0-12 h）, the fungal community had decreased abundance and minorly changed diversity. The abundance and diversity of the fungal community increased simultaneously during 12-24 h of fermentation, decreased simultaneously during 24-72 h, and elevated simultaneously during 72-96 h. Both reached the initial level of fermentation at 96 h. Within 12 h of fermentation, the pH value of the fermentation system dramatically reduced. It decreased at a slower rate during 12-48 h, and continued to slow down and became gentle during 48-96 h. Two fungal phyla, Ascomycota and Basidiomycota, were identified in the traditional koumiss by high-throughput sequencing targeting on the fungal rDNA-ITS sequence, with the relative abundances of 99.77% and 0.02%, respectively. During the fermentation process, Ascomycota was absolutely dominant. A total of 9 fungal genera were observed, among which Kazachstania and Kluyveromyces were the dominant ones, with the relative abundances of 95.76% and 3.75%, respectively. During 12-96 h of fermentation, the change of relative abundance of Kluyveromyces displayed an alternating trend with that of Kazachstania, and both were present during the whole fermentation process of 96 h. In addition, Kazachstania unispora, Kluyveromyces lactis and Kluyveromyces marxianus were the dominant ones among the 9 fungal species identified, with the relative abundances of 95.76%, 2.10% and 1.63%, respectively. The relative abundances of the 3 dominant species changed in varied manners at the different fermentation stages. [Conclusion] This study clarified the dominant fungal species as well as the succession characteristics of diversity and structure of fungal community during the fermentation process of traditional koumiss from Inner Mongolia. Our results provided a reference for enriching the research on fermentation mechanism, optimizing the fermentation process and improving the fermentation quality of koumiss.

Key words: Inner Mongolia, koumiss, fungi, microbial community structure, rDNA-ITS sequence, high-throughput sequencing