Effect of metal ion concentration on a biological reactor |
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Authors: | Ibbotson P G Spedding P L Otterburn M S |
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Affiliation: | Department of Chemical Engineering, Queen's University of Belfast, Belfast, Northern Ireland BT9 5AH. |
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Abstract: | Saccharomyces cerevisiae (yeast) cells were employed as a source of alcohol dehydrogenase in the NAD(+)-to-NADH reaction. The cells were immobilized in calcium alginate monofilament fibers and used in a biological reactor. The alginate could not be heat sterilized since temperatures above 80 degrees C caused the polymer chains to degrade. The same proved true for the high pH necessary for the reaction, but the alginate strength was increased by Ba(2+) solution treatment. X-ray probe analysis showed that about 30% of the Ca(2+) sites exchanged with the Ba(2+) ions. The Ba(2+) ions (as well as the Ca(2+) ions) permeabilized the cells and increased the reaction rate. Long term trials showed that Ba(2+) ions were slowly elutriated from the fiber biocatalyst, causing a drop in reaction rate. The trend certainly was reversible as far as the fiber was concerned. It is assumed that the permeabilization of the cells by the Ba(2+) ions was a reversible process. |
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