Study On The Biotransformation Of2-Phenylethanol By Active Dry Yeast

In this study, the biotransformation of2-phenylethanol (2-PE) from L-phenylalanine(L-Phe) by active dry yeast which was treated by rubbing and ultrasonic vibration wasstudied.First of all, analytical methods of carbon source, substrate, product and byproducts wereoptimized and established. In particular, gas chromatograph (GC) used to determine thecontent of ethanol,2-PE and PA was established. It was demonstrated that RSD was less than2%and the recovery was between97%~101%.Secondly, the accumulation mechanisms of2-PE was discussed by monitorring theconcentration changes of carbon source, substrate, product and byproducts in the synthesisprocess of2-PE. It was shown that the synthesis process of both ethanol and2-PE neededNADH. Besides, there existed some other degradation pathways for L-phenylalanine such ascinnamate pathway. The results indicated that higher concentration of L-Phe lowered themolar yield of2-PE from L-Phe Y2-PE/L-Phe(mol/mol). Additionally, both ethanol and2-PEinhibited the aryl-alcohol dehydrogenase (EC1.1.1.90). The toxic effect under theco-existence of ethanol and2-PE was much severe than that of ethanol or2-PE existenceindividually.Thirdly, according to the ccumulation mechanisms, in situ product removal techniques(ISPR) with the oxidation degradation of ethanol were generally adopted in2-PE productionto eliminate the the toxicity and inhibition originating from the accumulation of both ethanoland2-PE. To further enhance2-PE production by using glucose only, a novel operationstrategy to simultaneously control rates of glucose glycolysis and ethanol oxidativedegradation with the aid of ISPR techniques was developed. After controlling the fouroperation cycles, total2-PE concentration and Y2-PE/L-Phe(mol/mol) reached14.8g/l and0.83,respectively. The yield of2-PE on glucose Y2-PE/glucose(g/g) was0.12.Finally, the product after being isolated and purified was identified by GC-MS. The odordetection threshold and odoriferous quality of2-PE synthetized by different ways were alsotested. Results indicated that recognition threshold (RT) of2-PE produced by fermentationwas moderate and differed0.33μg/L from that of2-PE extracted from rose essential oil. Theodoriferous quality of2-PE was close enough to that extracted from rose with a similarity of95.88%.