Fermentation Process Optimization for High 2-Phenylethanol Aroma Whisky

2-Phenylethanol (2-PE) is a key aromatic alcohol contributing to the rose-like odor in brewed wines, primarily synthesized by yeast metabolism with a typical yield of less than 100 mg/L. To enhance the 2-PE content in brewed wines, this study used CRISPR-Cas9 gene editing technology to delete the ARO8 gene (encoding aromatic transaminase I) in Saccharomyces cerevisiae SY. The single-factor experiments were performed to optimize the fermentation process, and the 2-PE content in the brewed wine was measured by high-performance liquid chromatography. The results demonstrated that the 2-PE content in whisky fermented by the SY-A8 was 0.73 g/L, increasing 23.73% compared to SY. The fermentation conditions of SY-A8 were optimized through single-factor experiments and the Box–Behnken design. The optimal conditions were a sugar concentration of 46.30 g/L, a fermentation time of 6 days, and an L-phenylalanine concentration of 1.43 g/L. The high 2-phenylethanol aroma whisky was brewed with a higher 2-phenylethanol content of 3.68 g/L in a 1 L fermenter at the optimal conditions. In conclusion, the modification of Saccharomyces cerevisiae by CRISPR-Cas9 gene editing combined with fermentation process optimization provides an effective technical strategy for improving the 2-PE content in whisky, thereby providing a research perspective for the flavor enhancement of whisky and other brewed wines.