Comparison of microbial communities and amino acid metabolites in different traditional fermentation starters used during the fermentation of Hong Qu glutinous rice wine

Hong Qu glutinous rice wine (HQGRW) is produced from glutinous rice with the addition of the traditional fermentation starter Hong Qu (mainly Gutian Hong Qu and Wuyi Hong Qu) has been added. It is unpalatable and rejected by consumers because the bitter and umami tastes are too high. The objective of this study was to compare the dynamics of the microbial communities and amino acids especially those in the different traditional fermentation starters used during HQGRW fermentation, and elucidate the key microbes responsible for amino acids. Three widely-used types of Hong Qu starters were used which can make different bitterness and umami in our previous studies, namely, black Wuyi Hong Qu (WB), red Wuyi Hong Qu (WR), and Gutian Hong Qu (GT). The living dynamics of fungal and bacterial communities during the fermentation were determined by high-throughput sequencing and rRNA gene sequencing technology for the first time. The content of amino acids in the HQGRW were determined by reverse-phase high-performance liquid chromatography analysis. The results showed that there were differences between fungal communities during the fermentation process in Wuyi Hong Qu and Gutian Hong Qu starters and between bacterial communities during the fermentation process in the three types of starters. The amino acid content of the samples showed an increasing trend in each group. The total amino acids, as well as the bitter, sweet, umami, astringent amino acids, in the GT Hong Qu group increased more slowly during fermentation, as comparerd to those in WB and WR groups. Furthermore, Meyerozyma, Saccharomyces, Bacillus, Rhizopus, Pediococcus, Monascus, and Halomonas were strongly positively correlated with the content of bitter and umami amino acids (vertical bar r vertical bar > 0.6 with FDR adjusted P < 0.05) by Spearman's correlation analysis. To conclude, these findings may contribute to a better understanding of the bitter and umami amino acid production mechanism during traditional fermentation and helpful in improving the taste of HQGRW.