Effect of aerobiosis on fermentation and key enzyme levels during growth of Pichia stipitis,Candida shehatae and Candida tenuis on d-xylose |
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Authors: | James C du Preez Brian van Driessel Bernard A Prior |
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Institution: | (1) Department of Microbiology and Biochemistry, University of the Orange Free State, P.O. Box 339, ZA-9300 Bloemfontein, South Africa |
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Abstract: | The relationship between the degree of aerobiosis, xylitol production and the initial two key enzymes of d-xylose metabolism were investigated in the yeasts Pichia stipitis, Candida shehatae and C. tenuis. Anoxic conditions severely curtailed growth and retarded ethanol productivity. This, together with the inverse relationship between xylitol accumulation and aeration level, suggested a degree of redox imbalance. The ratios of NADH- to NADPH-linked xylose reductase were similar in all three yeasts and essentially independent of the degree of aerobiosis, and thus did not correlate with their differing capacities for ethanol production, xylitol accumulation or growth under the different conditions of aerobiosis. Under anoxic conditions the enzyme activity of Pichia stipitis decreased significantly, which possibly contributed to its weaker anoxic fermentation of xylose compared to C. shehatae. |
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Keywords: | d-Xylose fermentation" target="_blank">d-Xylose fermentation Aeration level Xylose reductase Xylitol dehydrogenase Yeast Candida shehatae Candida tenuis Pichia stipitis |
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