Kluyveromyces lactis and Kluyveromyces marxianus are industrial yeasts widely used in the production of the b-galactosidase enzyme. Biosynthesis of b-galactosidase is controlled by glucose repression. In this study it was demonstrated that the derepression of b-galactosidase biosynthesis in these yeast strains is inhibited by high osmotic stress. It was found that the b-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 b-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 b-galactosidase biosynthesis in K. lactis, while nitrogen starvation led to a 2-fold increase in b-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.

Kluyveromyces lactis and Kluyveromyces marxianus are industrial yeasts widely used in the production of the b-galactosidase enzyme. Biosynthesis of b-galactosidase is controlled by glucose repression. In this study it was demonstrated that the derepression of b-galactosidase biosynthesis in these yeast strains is inhibited by high osmotic stress. It was found that the b-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 b-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 b-galactosidase biosynthesis in K. lactis, while nitrogen starvation led to a 2-fold increase in b-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.