Cr (VI) Ion Uptake by the Yeast S. Cerevisiae UCM Y-1968 and its Protoplasts

The present study is focused on the investigation of hexavalent chromium uptake by the yeast S. cerevisiae UCM Y–1968 and its protoplasts. For the first time the ability of S. cerevisiae protoplasts to accumulate Cr (VI) ions was shown. Under the influence of various concentrations of Cr (VI) ions, the proportion of the surviving yeast cells and protoplasts decreased as treatment time extended. During 0.5 – 1h of treatment, yeast protoplasts demonstrated a significant level of Cr (IV) ion accumulation, 44 – 47 % of the supplied Cr ions, whereas the initial strain S. cerevisiae UCM Y-1968 accumulated 9 – 10 %. The isotherms for S. cerevisiae UCM Y-1968 were related to L2 types and for yeast protoplasts isotherms were related to L3 types. Cr (VI) sorption/uptake parameters (Qmax, b) for living cells were found for S. cerevisiae UCM Y–1968 (Qmax = 890 μmol/g) and its protoplasts (Qmax = 1335 μmol/g) at the initial Cr (VI) ions concentration of 25 mg/l. The results showed that hexavalent chromium uptake by living yeasts biomass mainly depended on intracellular accumulation. Chromium uptake by protoplasts cells was characterized by simultaneous metabolism-dependent bioaccumulation with prevalence of the intracellular accumulation of Cr (VI) ions.

A Method of Isolating Anucleated Yeast Protoplasts Unable to Synthesize the Glucan Fibrillar Component of the Wall

A mixture of nucleated and anucleated protoplasts was produced from log-phase Saccharomyces cerevisiae by the use of snail enzymes. The mixture was separated by centrifugation, and anucleated protoplasts were studied by means of light and electron microscopy. Anucleated protoplasts did not synthesize glucan fibrils even though they seemed to contain all other basic structures in their cytoplasm, and the structure of the plasma membrane was unchanged. This was in sharp contrast to ordinary nucleated protoplasts which synthesized glucan fibrils even after inhibition of protein synthesis by cycloheximide. The reason for this behaviour of anucleated protoplasts is not clear. Such anucleated yeast protoplasts represent the first example of uniform anucleated fungi produced by a reproducible method.

Characterization of fusion products from protoplasts of yeasts and their segregants by electrophoretic karyotyping and RAPD

In order to characterize fusion products from yeast protoplasts and their segregants, with important features to the wine making industry, electrophoretic karyotyping and RAPD (Random Amplified Polymorphic DNA) were utilized. Electrophoretic karyotyping was performed by the CHEF ("contour-clamped homogeneous electric field electrophoresis") method, which allowed the detection of chromosomal band complementation in fusion products and the presence of patterns of both parental and intermediary strains in segregants. By utilizing two primers, an amplification pattern of DNA fragments was obtained. While fusion products (diploid) showed a pattern of complementary bands, segregants showed bands of either parental strains or even intermediary bands