An epimerasic activity on galactose induced by xylose inKluyveromyces sp |
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Authors: | María Edith Elorza De Orellano Ana María Ponce De Ascheri María Isabel Sanz De Tosetti Rodolfo Segovia |
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Institution: | (1) Laboratorio de Fermentaciones Industriales, Cátedra de Microbiologia Industrial, Facultad de Quimica, Bioquimica y Farmacia UNSL, 5700 San Luis, Argentina |
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Abstract: | Production of galactose epimerase by anKluyveromyces sp. isolated from Kefir (dairy product) was investigated in batch culture. The microorganism was cultured in media with 1%
galactose, 1% xylose, or 0.5% xylose plus 0.5% galactose, in Erlenmeyer flasks shaken at 200 rpm and maintained at 30°C. After
48 h, the biomass was harvested by centrifugation and permeated with 80% ethanol. Permeated cells were suspended in 0.1M sodium
phosphate buffer pH 6.5. A part of this suspension was shaken for 17h at 140 rpm. The supernatant, free of cells, was separated.
Partial characterization ofKluyveromyces sp. epimerase was carried out in the cellular suspension and the supernatant solution. Enzymatic activity, using galactose
as substrate, was measured. The product of this reaction was measured by the use of glucose oxidase. The results indicated:
(1) there was a strong effect of xylose on induction of epimerase activity; (2) the epimerase obtained was independent of
the energetic cell activity; (3) the epimerase activity in whole cells was similar to the activity obtained from the supernatant;
(4) epimerase showed a typical substrate-inhibition curve and dependence on magnesium; and (5) the best pH range was between
5.5 and 6.5 and the optimal temperature was 30°C. |
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Keywords: | Epimerase galactose Kluyveromyces sp xylose |
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