Profiling the potential producers of higher alcohol in different Daqu (a starter of Baijiu) by amplifying the key enzyme gene

Higher alcohols are not only the key flavor substance but also the precursor of other flavor substances in Baijiu. In the metabolic pathway of higher alcohols, alcohol dehydrogenase (ADH) plays an important role and its genes can be used as a marker gene for analyzing the producer of higher alcohols. In this study, the degenerate primers of Zinc-dependent long-chain ADH gene (L.<i>adh</i>) were designed and applied to investigate the diversity of L.<i>adh</i> in different Daqu (HT, SC and SD). The results showed that the degenerate primers were able to amplify the fragment of L.<i>adh</i> and had good coverage in high-throughput sequencing. The diversity and composition of L.<i>adh</i> in the three kinds of Daqu were different and the diversity of L.<i>adh</i> in SC was the highest while HT was the lowest. The predominant L.<i>adh</i> in SC and HT were form <i>Bacillus</i> (54%–78%) and <i>Aspergillus</i> (64%–66%), respectively, and the predominant L.<i>adh</i> in SD were from <i>Aspergillus</i> (7%–51%) and <i>Enterobacter</i> (2%–47%). In addition, L.<i>adh</i> from bacteria and fungi could be clustered into one evolutionary branch and divided into 10 clusters. The findings of this study will provide a new perspective for evaluating the potential microorganisms associated with higher alcohol synthesis in Daqu and reference for selecting suitable Daqu in the production of Baijiu.