Screening of High-yielding Tetramethylpyrazine Bacillus and Its Effect on the Accumulation Process of Maotai-flavor Liquor

In order to increase and stabilize the content of tetramethylpyrazine in liquor, 13 strains of Bacillus were isolated from Maotai Daqu samples, and 5 strains with excellent protease production were selected through the preliminary screening of protease transparent circle test. After a liquid fermentation test, a functional bacterium with high yield of tetramethylpyrazine was screened out. The content of tetramethylpyrazine in the fermentation broth was 12.22 mg/L, which was identified as Bacillus licheniformis GTBL-168. The seed culture solution of this strain was inoculated into the sauce-flavor liquor accumulation culture at 0%, 3%, 5%, and 7% (v/w) to synergize the fermentation with traditional Daqu, and accumulate acetoin and tetramethyl in the glutinous rice grains. The content of pyrazine increased, and the increasing was the largest when the inoculation amount was 7%, and the yield of tetramethylpyrazine increased by 24.88% compared with the control group, the overall changes in physical and chemical indexes were obvious, and the amino nitrogen and total acid increased, the addition of Bacillus licheniformis GTBL-168 had little effect on the microbial structure of the accumulated fermented grains. With the increasing of the inoculation amount, the abundance of Bacillus and other dominant bacteria in the fermented grains also increased. It would lay a foundation for the application of functional bacteria in the process of stacking fermentation.