The Effects Of Major Functional Microbial Succession On Tetramethylpyrazine During The Traditional Brewing Process Of Liangzhou Fumigated Vinegar

Tetramethylpyrazine was one of the major flavor compounds of Liangzhou fumigated vinegar(Gansu province), and it could be generated from the microbial metabolism during the fermentation process. In this study, we combined the traditional separation culture method and the high throughput sequencing technology to learn the succession and diversity of the function microbial. At the same time, we dynamically tracked and analyzed the relative content change of tetramethylpyrazine during the brewing process of the Liangzhou fumigated vinegar with the solid-phase micro extractions-gas chromatography mass spectroscopy(SPME-GC-MS) method. On the basis of the results, we adopted the correlation analysis to study the influence of the succession of the function microbial on the tetramethylpyrazine, and used the functional microorganisms separated from the different fermentation process of Liangzhou fumigated vinegar to simulate the solid state fermentation test, in order to supply the theoretical foundation for exploring the flavor formation mechanism during the Liangzhou fumigated vinegar fermentation process, and provided the technical assistance so that it would improve the flavor and quality. The main results are following:1. The variation of fundamental physicochemical indexes of cultures during different process of the Liangzhou fumigated vinegar were found out. It was showed that the temperature, alcoholicity and reducing sugar content all increased at the beginning and then stepped down, the content of starch gradually decreased during the fermentation process. Besides, pH decreased, but the content of total acid and amino acid nitrogen increased, the moisture basically maintained constant.2. The structer and distribution of dominant microorganisms in daqu have been researched clearly. Results showed that the dominant microbes of daqu were Monascus,Aspergillu,Bacillus,Thermoactinomyces and Streptomyces, ect.3. The diversity and succession of the microorganisms in Liangzhou fumigated vinegar brewing process were specified. It demonstrated that the microbial community composition changed little in the first 3 days, Saccharomycetes and Lactobacillus were the main dominant microorganisms in this period; the 3~8 days was a transition period of ethanol fermentation to acetic acid fermentation, during this stage, the structure of microbes composition changed quickly, so the microbial constitute varied in the different cultures; and the composition of microorganisms also had little change in 8~13 days, Acetobacter and Alternaria were the main dominant microorganisms. Besides, Venn showed that during the Liangzhou fumigated vinegar fermentation, the bacteria came mainly from the fermentation environment while the fungus came mainly from daqu.4. The influences of the major functional microbes on the relative content of tetramethylpyrazine in the Liangzhou fumigated vinegar fermentation were analyzed. Correlation analysis results showed that there was significant positive correlation between Acetobacter and acetoin and extremely significant positive correlation among the Acetobacter and the isothiocyanate butyl ester; Saccharomyces was actively interrelated with the acetion and negatively interrelated with isothiocyanate butyl ester; Lactobacillus involved in the metabolism of the acetoin but negatively interrelated with the tetramethylpyrazine.5. Simulating fermentation tests were carried out in solid-state by inoculating the functional microbes to check out the impacts for vinegar flavor. The results showed that yeast, acetic acid bacteria, lactic acid bacteria and bacillus all had certain affects on the generation of tetramethylpyazine, yeast could metabolize precursor of the tetramethylpyazine: acetoin and 2, 3-butanediol, while acetic acid bacteria, lactic acid bacteria and bacillus bacteria could utilize feed grains nutrients to metabolize tetramethylpyazine.In conclusion, Liangzhou fumigated vinegar fermentation was a process of mixed fermentation of multi-strains, and the structures of microorganisms were many differences among the different fermentation process. Aspergillus, Saccharomyces, Lactobacillus, Acetobacter and Bacillus were dominant microorganisms during the Liangzhou fumigated vinegar fermentation process, all of which affected the synthesis and metabolism of tetramethylpyazine.