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Influence of temperature and pH on xylitol production from xylose by Debaryomyces hansenii UFV-170

Paper ID Volume ID Publish Year Pages File Format Full-Text
36391 45131 2006 7 PDF Available
Title
Influence of temperature and pH on xylitol production from xylose by Debaryomyces hansenii UFV-170
Abstract

The effects of temperature and starting pH on xylose-to-xylitol bioconversion by the new yeast isolate Debaryomyces hansenii UFV-170 were investigated. The optimum pH resulted to be in the range 4–8, being the maximum production of xylitol (Pm) 37.5–41.8 g l−1, volumetric productivity (QP) 0.70–1.0 g l−1 h−1, specific productivity (qP) 0.19–0.30 g g−1 h−1 and xylitol yield on consumed xylose (YP/S) 0.70–0.76 g g−1. The percentage of xylose consumed for xylitol production progressively increased with pH, whereas those associated to both biomass growth and catabolic reaction through the TCA cycle decreased, reaching nearly constant values at pH 4.0. The optimum temperature range for xylitol production (Topt) was 30–35 °C, under which conditions the yeast exhibited YP/S  =  0.74–0.77 g g−1, QP = 0.96–1.1 g l−1 h−1 and qP = 0.26–0.40 g g−1 h−1, whereas the process was hardly affected either at lower (10–20 °C) or higher (40–45 °C) temperatures. At low temperature (15 °C), the largest percentages of xylose were consumed by the catabolic reaction through the TCA cycle (46%) and for biomass production (43%), while xylitol formation became the most significant activity at 20 °C, further increased up to 30–35 °C and then decreased over 40 °C. The results collected at variable temperature were finally used for estimation of the main thermodynamic parameters of the system: the activation enthalpy and entropy of xylitol formation were 96.1 kJ mol−1 and −0.008 kJ mol−1 K−1, while the standard enthalpy and entropy of thermal inactivation were 294 kJ mol−1 and 0.89 kJ mol−1 K−1, respectively.

Keywords
Debaryomyces hansenii; Xylose-to-xylitol bioconversion; pH; Temperature; Carbon material balances; Thermodynamics
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Publisher
Database: Elsevier - ScienceDirect
Journal: Process Biochemistry - Volume 41, Issue 3, March 2006, Pages 675–681
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us