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Aims:  Screening for a robust, stress tolerant Saccharomyces cerevisiae strain for production of 2‐phenylethanol (PEA) from l‐phenylalanine. Methods and Results:  Saccharomyces cerevisiae natural isolates that include thermotolerant and multi‐stress resistant strains were screened for production of PEA. The strains were compared by their growth rate, maximum biomass dry weight and production yields, and it was shown that high biomass is required for obtaining high concentrations of PEA. One thermotolerant strain, Ye9‐612, was the most efficient, and under optimal conditions produced 0·85 g l−1 PEA in shaking flasks, and 4·5 g l−1 in a fed‐batch fermentation. Strain Ye9‐612 was also found to be tolerant to high concentrations of PEA, and maintained high biomass dry weight in the presence of 2·5 g l−1 PEA. Conclusions:  We found a highly productive thermotolerant S. cerevisiae strain that is resistant to high concentrations of PEA. Significance and Impact of the Study:  PEA is inhibitory to growing yeast cells and therefore a robust strain is needed for excessive industrial production. This is the first description of such a stress tolerant strain, and the PEA concentration obtained in the fermentation is the highest reported to date.

2-Phenylethanol (PEA) is a commercial flavor and fragrance compound, with a rose-like odor, used in the cosmetics and food industries. Saccharomyces cerevisiae strains produce PEA in a growth-associated manner but are prone to product inhibition, resulting in low production yields. The aim of this study was to use immiscible ionic liquids (ILs) in a biphasic system to enhance the PEA concentration by means of in situ product removal (ISPR). Nine ILs were tested for their influence on growing yeast cells, and five of them were found to be biocompatible. A correlation between the IL structure and the effect on yeast growth was investigated. [Tf(2)N] anions were found to be the most biocompatible in comparison to [PF(6)] and [BF(4)], and the pyridinium and ammonium cations were slightly preferable than the imidazolium cation. Furthermore, the longer the alkyl side chain on the imidazolium ring, the less it is biocompatible, with major significance above six carbons. The five biocompatible ILs were tested for PEA recovery capability by determining their distribution coefficients (K(D)), with the highest value of 17.6 obtained for BMIM[Tf(2)N]. Finally, ILs were tested for their efficiency as ISPR solvents under stress conditions of a high product concentration. A 3-5-fold increase in the total PEA concentration produced by the cells was obtained with MPPyr[Tf(2)N], OMA[Tf(2)N], and BMIM[Tf(2)N], demonstrating the potential of ILs for enhancing productivity in bioprocesses using growing cells.

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Tyrosinases are type 3 copper enzymes that are involved in the production of melanin and have two copper ions in the active site. Here, the crystallization and primary analysis of a tyrosinase fromBacillus megateriumis reported. The purified protein was crystallized in the absence or presence of zinc ions and the crystals diffracted to a resolution of 2.0 Å. Crystals obtained in the presence of zinc belonged to space groupP212121, while crystals grown in the absence of zinc belonged to space groupP21. In both space groups the asymmetric unit contained a dimer, with minor differences in the crystal density and in packing interactions.