Extra-cellular chromate-reducing activity of the yeast cultures |
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Authors: | Helena P Ksheminska Taras M Honchar Galyna Z Gayda Mykhailo V Gonchar |
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Institution: | (1) Department of Cell Regulatory Systems, Institute of Cell Biology, National Academy of Sciences of Ukraine, Lviv, 79005, Ukraine |
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Abstract: | This paper reports on the experimental data supporting an essential role of extra-cellular reduction in chromate detoxification
by baker’s and non-conventional yeasts. A decrease of chromate content in the yeast culture coincides with an increase of
Cr(III) content in extra-cellular liquid. At these conditions, cell-bound chromium level was insignificant and a dominant
part of extra-cellular Cr(III) species was detected in the reaction with chromazurol S only after mineralization of the cell-free
samples. This phenomenon of chromium “disappearance” can be explained by the formation of Cr(III) stable complexes with extra-cellular
yeast-secreted components which are “inaccessible” in the reaction with chromazurol S without mineralization. It was shown
that increasing sucrose concentration in a growth medium resulted in an increase of chromate reduction. A strong inhibition
of chromate reduction by 0.25 mM sodium azide, a respiration inhibitor and a protonophore, testifies that extra-cellular chromate
detoxification depends on energetic status of the yeast cells. It was shown that Cr(III)-biochelates produced in extra-cellular
medium are of a different chemical nature and can be separated into at least two components by ion-exchange chromatography
on anionit Dowex 1x10. A total yield of the isolated Cr(III)-biocomplexes is approximately 65 % (from initial level of chromate)
with a relative molar ratio 8:5. |
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Keywords: | Chromate chromium(III) chromium(III)-biocomplexes extra-cellular medium reduction yeast |
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