Screening of a high-yield β-phenylethanol yeast and optimization of its cultural conditions

Objective: A yeast with high-yield for β-phenylethanol was isolated and purified from Daqu, and the fermentation conditions of β-phenylethanol produced from it were optimized. Methods: The high-yield β-phenylethanol yeast was isolated and purified by traditional microbial separation; then the yeast was identified by the morphological and physiological characteristics and its 26 S r DNA D1/D2 sequence.The factors including L-phenylalanine, yeast extract, temperature and initial p H, that affected the yield of β-phenylethanol, were studied in single factor optimization test.On the basis of single factor test, the conditions for β-phenylethanol production were explored by Box-Behnken design involving the yeast extract, temperature and initial p H at three levels in combination with response surface methodology.Results: A yeast designated as Y1511 with high-yield for β-phenylethanol was isolated and purified from strong-flavor Daqu, then the yeast was identified as types of Pichia kudriavzevii.It was tested for arom production in bean sprouts medium, and there were nearly thirty kinds of volatile components present in the fermentation of medium.By the experiments of single factor and Box-Behnken design, the optimal conditions forβ-phenylethanol production were as follows: glucose 80 g/L, Mg SO40.5 g/L, KH2PO45 g/L, L-phenylalanine 10 g/L, yeast extract 5.5 g/L and initial p H5, incubated at 26 ℃.Under the condition, the yeast Y1511 yielded β-phenylethanol of 3.25 g/L.Conclusion: This is the first report about β-phenylethanol production of P.Kudriavzevii from strong-flavor Daqu.