EHRLICH PATHWAY STUDY IN SACCHAROMYCES AND KLUYVEROMYCES YEASTS

The growth and 2-phenylethanol (2-PE) biosynthesis of three ascomycetous yeasts belonging to the genera Saccharomyces and Kluyveromyces, able to synthesize 2-PE, was studied The key growth kinetic parameters were calculated and the comparison of the obtained results revealed that the newly isolated K. marxianus 35 strain had higher potential for 2-PE production. It was characterized with a lower growth yield coefficient and a higher substrate uptake rate and 2-PE production rate in comparison with the other two yeast strains. The assays of key enzymes from the Ehrlich pathway (aminotransferase, pyruvate decarboxylase and alcohol dehydrogenase) showed that K. marxianus 35 also expresses a nearly two-fold higher level of activities. Furthermore, the biotransformation capacity for 2-PE production was investigated through measurement of 2-Phe residual concentration. This concentration was two-fold lower in K marxianus 35 and the efficiency was found to be 73 % for this strain. These values for K. marxianus 1984 and S. cerevisiae 584 were 58 % and 32 %, respectively. In order to comprehensively examine the potential of K. marxianus 35 for 2-PE biosynthesis, the sequence variability in the genes encoding key enzymes from the Ehrlich pathway were investigated The obtained data suggest that, apart from physiological advantages gained, Kluyveromyces yeasts have probably undergone substantial evolutionary gene alterations resulting in higher enzymatic activities and better 2-PE transformation potential. Based on the performed comparative analysis, it was shown that among the studied 2-PE producers, K. marxianus 35 has several advantages which make this strain a promising candidate for industrial processes.