Studies On The Tolerance Of Yeast To 2-Phenylethanol And Screening Of Mutant For High Production Of 2-Phenylethanol

2-phenylethanol is an important flavour and flagrance compound with a rose-like odour.It is widely used in food,cosmetics,tobacco and chemical Industries.Since natural 2-phenylethanol is preferred by more and more people,the production of natural 2-phenylethanol by transformation with yeast is the way to reach greater market prospect and application value.But the inhibition of 2-phenylethanol to yeast is one of the most difficult problems in the production of 2-phenylethanol by Saccharomyces cerevisiae.13 yeast strains from lab collection were screened for the tolerance to 2-phenylethanol and the production of 2-phenylethanol from L-Phe. Saccharomyces cerevisiae CWY132 was screened out for its high tolerance to 2-phenylethanol and high yield of 2-phenylethanol.Saccharomyces cerevisiae CWY132 was treated by Ultraviolet radiation,and ten resistance mutants were screened out.Studies on the relations between the resistance and the yield of 2-phenylethanol showed that one of the mutant strain,named CWY132-10 with the highest tolerance to 2-phenylethanol（2 g/L）and highest yield of 2-phenylethanol （3.3 g/L）,its resistance was inceased by 50%and the yield of 2-phenylethanol increased by 9.1%compared with the original strain. The S.cerevisiae CWY132-10 mutant was further treated with Ultraviolet radiation,⁶⁰Coγirradiation and N⁺ ion.One mutant strain,named CWY132-10-γ2 was screened out with the highest tolerance to 2-phenylethanol and highest yield of 2-phenylethanol,which can grow on the medium containing 3.5 g/L of 2-phenylethanol and the yield of 2-phenylethanol reached to（3.81 g/L）increased by 15.1%compared with the original strain,with the molar conversion rate was 97%.Optimization of 2-phenylethanol biotransformation condition for CWY132-10-γ2 was carried out by Uniform design,and the production of 2-phenylethanol was further increased to 3.9 g/L.During the screening for the tolerant mutant to 2-phenylethanol,one of the copies of ARO9 gene in Saccharomyces cerevisiae CWY132 was deleted,and the yield of 2-phenylethanol in this strain was decreased by 12%.Another copy of this gene must be deleted to further study the function of ARO9 in the production of 2-phenylethanol.