Exploring, Cloning, and Characterization of Aryl-alcohol Dehydrogenase for β-Phenylethanol Production in Paocai

β-Phenylethanol is the primary flavor compound in Sichuan industrial paocai. Metatranscriptomics analysis revealed that the gene encoding aryl-alcohol dehydrogenase (AADh1), which is responsible for β-phenylethanol synthesis, had the highest expression level during the late stage of fermentation (180 days). In the present study, we explored the potential AADh1 in Sichuan industrial qingcai paocai by combining metatranscriptomics results and AADh1 analysis in NCBI. AADh1 was successfully cloned and expressed in Escherichia coli BL21, and the enzymatic properties of AADh1 were characterized. AADh1 exhibited the highest activity at pH 7.0 and 50°C, with the highest stability at pH 8.0 and 25°C. Furthermore, the enzyme exhibited low tolerance to metal ions, and only 1 mM Mn2+ could slightly activate the enzyme. Moreover, AADh1 was successfully used to preliminarily enhance the β-phenylethanol of industrial paocai, which could improve the flavor of paocai to a certain extent in practical production.