Abstract: In this study, high-throughput sequencing technology and statistical analysis were employed to explore the effects of adding green tea at proportions of 10%, 20%, and 30% on physicochemical characteristics, bacterial community diversity and succession of Daqu during fermentation compared with pure wheat Daqu (control). The results showed that the addition of green tea significantly increased the bacterial community diversity of Daqu and improved its saccharification capacity, moisture content and acidity. However, the increase in tea addition did not exhibit a proportional relationship with the community diversity. The unique evolutionary structure of the bacterial communities in different types of Daqu was found to be the major factor affecting the physicochemical characteristics of Daqu. During the fermentation process, all four Daqu exhibited differentiation in bacterial community succession starting from the thermophilic stage, thereby leading to the formation of their unique community structure at the end of the fermentation process. The phyla Proteobacteria, Firmicutes, Bacteroidota, and Actinobacteria showed varying influences on the community succession of the four Daqu samples, thus making each of them have different physicochemical characteristics. Specifically, Pseudomonas was an important bacterial genus contributing to the physicochemical characteristics of the control and 10% tea Daqu, while Weissella and Pediococcus, were important contributors to the physicochemical characteristics of the 20% tea Daqu. Bacillus was found to be a significant bacterial genus contributing to the physicochemical characteristics of the 30% tea Daqu. This study provides a theoretical basis for process optimization in the production of tea-added Daqu and for the development of multi-raw material fermentation starters. It also has implications for improving the preparation process of Daqu and the application of tea in Daqu making.

Key words: community succession; physicochemical parameters; community diversity; community structure; dominant microflora