Yeast Tolerance to Chromium Depends on Extracellular Chromate Reduction and Cr(III) Chelation

• Main Authors: Halyna Ksheminska, Daria Fedorovych, Taras Honchar, Maria Ivash, Mykhailo Gonchar
• Format: Article
• Language: English
• Published: University of Zagreb 2008-01-01
• Series: Food Technology and Biotechnology
• Subjects: yeast; Pichia guilliermondii; chromate tolerance; medium composition; chromate reduction; chromium(III) chelation
• Online Access: http://hrcak.srce.hr/file/48129

The sensitivity of the yeast Pichia guilliermondii ATCC 201911 (L2) to Cr(VI) and Cr(III) has been investigated. This yeast was demonstrated to have much higher resistance to Cr(III), compared to Cr(VI). At chromate level of 2.0 mM, an expanded lag phase in growth was observed, followed by the active phase of cell proliferation. During the growth arrest, a residual external chromate concentration decreased gradually to the nontoxic level, and the duration of this period was directly dependent on the initial Cr(VI) concentration in the medium, i.e. the higher the Cr(VI) level, the longer the growth delay. Thus, the tolerance of P. guilliermondii to chromate depends on its capacity for extracellular reduction of Cr(VI). As a product of chromate reduction, Cr(III) forms complexes with the components of culture liquid, which are not effectively adsorbed by the cells and do not repress the growth of P. guilliermondii. When urea is used as a nitrogen source, not only chromate reduction, but also Cr(III) chelation were shown to decrease, compared to the medium supplemented with ammonium sulphate. The experimental data confirm this concept of extracellular reduction of Cr(VI) as an important mechanism, which provides the resistance of yeast cells to chromate.