Author
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Saha, Badal |
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Bothast, Rodney |
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Submitted to: Journal of Industrial Microbiology and Biotechnology
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 3/18/1999 Publication Date: N/A Citation: N/A Interpretive Summary: Xylitol is a sugar alcohol used as a natural food sweetener, dental caries reducer, and as an alternative sugar for diabetics. Xylitol is currently produced by a chemical process from wood. Drawbacks of the chemical process are requirements for high pressure and temperature, use of an expensive catalyst, and use of extensive separation and purification steps to remove the by-products formed during chemical reduction. Because of these problems, the production of xylitol by fermentation of xylose, available in various agricultural residues such as corn fiber, is becoming attractive. We found that the yeast Candida peltata NRRL Y-6888 produced a good yield of xylitol from xylose. The yeast appears to be a promising candidate for fermentative production of xylitol from xylose. Technical Abstract: The ability of Candida peltata NRRL Y-6888 to ferment xylose to xylitol was evaluated under different environmental conditions such as pH, temperature, aeration, substrate concentration, and in the presence of glucose, arabinose, ethanol, methanol, and organic acids. A maximum xylitol yield of 0.56 g/g xylose was obtained when the yeast was cultivated at pH 6.0, 28 deg C and 200 rpm on 50 g/L xylose. The yeast produced ethanol (0.41 g/g in 40 h) from glucose (50 g/L) and arabitol (0.55 g/g in 87 h) from arabinose (50 g/L). It preferentially utilized glucose > xylose > arabinose from mixed substrates. Glucose (10 g/L), ethanol (7.5 g/L), and acetate (5 g/L) inhibited xylitol production by 61, 84, and 68%, respectively. Arabinose (10 g/L) had no inhibitory effect on xylitol production by the yeast. |
