| Influence of temperature and pH on xylitol production from xylose by Debaryomyces hansenii. | |
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MedLine Citation:
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PMID: 11536125 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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The production of xylitol from concentrated synthetic xylose solutions (S(o) = 130-135 g/L) by Debaryomyces hansenii was investigated at different pH and temperature values. At optimum starting pH (pH(o) = 5.5), T = 24 degrees C, and relatively low starting biomass levels (0.5-0.6 g(x)/L), 88% of xylose was utilized for xylitol production, the rest being preferentially fermented to ethanol (10%). Under these conditions, nearly 70% of initial carbon was recovered as xylitol, corresponding to final xylitol concentration of 91.9 g(P)/L, product yield on substrate of 0.81 g(P)/g(S), and maximum volumetric and specific productivities of 1.86 g(P)/L x h and 1.43 g(P)/g(x) x h, respectively. At higher and lower pH(o) values, respiration also became important, consuming up to 32% of xylose, while negligible amounts were utilized for cell growth (0.8-1.8%). The same approach extended to the effect of temperature on the metabolism of this yeast at pH(o) = 5.5 and higher biomass levels (1.4-3.0 g(x)/L) revealed that, at temperatures ranging from 32-37 degrees C, xylose was nearly completely consumed to produce xylitol, reaching a maximum volumetric productivity of 4.67 g(P)/L x h at 35 degrees C. Similarly, both respiration and ethanol fermentation became significant either at higher or at lower temperatures. Finally, to elucidate the kinetic mechanisms of both xylitol production and thermal inactivation of the system, the related thermodynamic parameters were estimated from the experimental data with the Arrhenius model: activation enthalpy and entropy were 57.7 kJ/mol and -0.152 kJ/mol x K for xylitol production and 187.3 kJ/mol and 0.054 kJ/mol x K for thermal inactivation, respectively. |
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Authors:
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A Converti; J M Domínguez |
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Publication Detail:
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Type: Journal Article |
Journal Detail:
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Title: Biotechnology and bioengineering Volume: 75 ISSN: 0006-3592 ISO Abbreviation: Biotechnol. Bioeng. Publication Date: 2001 Oct |
Date Detail:
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Created Date: 2001-09-05 Completed Date: 2001-12-04 Revised Date: - |
Medline Journal Info:
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Nlm Unique ID: 7502021 Medline TA: Biotechnol Bioeng Country: United States |
Other Details:
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Languages: eng Pagination: 39-45 Citation Subset: IM |
Copyright Information:
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Copyright 2001 John Wiley & Sons, Inc. |
Affiliation:
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Department of Chemical and Process Engineering G.B. Bonino, University of Genoa, Via Opera Pia 15, 16145 Genoa, Italy. converti@unige.it |
Export Citation:
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| MeSH Terms | |
Descriptor/Qualifier:
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Carbon
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metabolism Entropy Ethanol / metabolism Hydrogen-Ion Concentration Saccharomycetales / metabolism* Temperature Xylitol / biosynthesis* Xylose / metabolism* |
| Chemical | |
Reg. No./Substance:
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0/Xylose; 64-17-5/Ethanol; 7440-44-0/Carbon; 87-99-0/Xylitol |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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