The Effect of Hyperosmotic Stress and Nitrogen Starvation on Growth and \beta-Galactosidase Synthesis in Kluyveromyces lactis and Kluyveromyces marxianus


Abstract: Kluyveromyces lactis and Kluyveromyces marxianus are industrial yeasts widely used in the production of the \beta-galactosidase enzyme. Biosynthesis of \beta-galactosidase is controlled by glucose repression. In this study it was demonstrated that the derepression of \beta-galactosidase biosynthesis in these yeast strains is inhibited by high osmotic stress. It was found that the \beta-galactosidase activity of K. lactis and K. marxianus remained approximately at the repressed level when these yeast cells were subjected to NaCl-, KCl-, or sucrose-induced high osmotic stress. Derepression of \beta-galactosidase biosynthesis seems to be more sensitive to high osmotic stress in K. marxianus than in K. lactis. In addition, it was shown that nitrogen starvation resulted in a significant decrease in the level of \beta-galactosidase biosynthesis in K. lactis, while nitrogen starvation led to a 2-fold increase in \beta-galactosidase biosynthesis in K. marxianus. Results of this study indicated that high levels of NaCl, but not sucrose, inhibited the growth of K. lactis and K. marxianus.

Keywords: Kluyveromyces, \beta-galactosidase, osmotic stress, nitrogen regulation, glucose repression

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