Studies On The Production Of 2-Phenylethanol By Transformation With Yeast

2-phenylethanol(PEA) is an important flavour and fragrancecompound with a rose-like odour. It is widely used in pharmaceutical,food, cosmetics, tobacco and chemical Industries. Since natural PEA ispreferred by more and more people, the production of natural PEA bytransformation with yeast is the way to reach greater market prospect andapplication value.12 industrial yeast strains from lab collection were screened for theproduction of PEA from L-Phe. Up to 1g/L PEA were obtained with twoof the strains, which were identified as S.cerevisiae AS 2.516 andS.cerevisiae GER based on the restriction fragment length polymorphism(RFLP) analysis of the 5.8S rDNA-ITS region.Rapid detecting method was established, which based on the extraction of PEA from fermentation suspension by chloroform. Theconfirmation tests compared with HPLC results showed this method isaccurate enough for screening a large amount of mutants of S.cerevisiaeAS 2.516 for their PEA contents.Uniform design was carried out for the optimization of mediumcomponents and culture conditions, 1.8 g/L PEA was yielded when thetransformation was under the optimal conditions. Further optimized theconcentration of KH₂PO₄ and the transformation period, the production ofPEA increased to 2.13 g/L, with the molar conversion rate of 57.6%.UV mutation of S.cerevisiae AS 2.516 was carried out. Using rapiddetecting method, 167 mutants were screened for their PEA production.The mutant with the highest PEA yield was designated as S.cerevisiaeCWY132, the production of PEA under the optimal conditions reached3.52 g/L, with a high conversion rate of 95.3%.Transformation with higher concentration of L-phenylalanine(L-Phe) was examined combined with in situ product removal. 10 g/LL-Phe was put into the flask system and polypropylene glycol 1500 (PPG-1500) was coexisted in the system as the in situ extractant, 5.35 g/L PEAcould be yielded in a certain volume of PPG-1500, with the conversionrate of 72.3%. 5L Biostat fermentor test was also carried out with 10 g/LL-Phe and with equal volume of PPG-1500 as in situ extractant, 5.71 g/LPEA was yielded with the high conversion rate of 77.2%.