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Title: Enzymic degradability of hull-less barley flour alkali-solubilized arabinoxylan fractions by endoxylanases
Authors: Trogh, Isabel ×
Croes, Evi
Courtin, Christophe
Delcour, Jan #
Issue Date: 2005
Publisher: Amer chemical soc
Series Title: Journal of Agricultural and Food Chemistry vol:53 issue:18 pages:7243-7250
Abstract: The impacts of the arabinose to xylose (A/X) ratio of arabinoxylans (AX) and the endoxylanase substrate specificity on the enzymic degradability of hull-less barley flour AX by endoxylanases were studied by using alkali-solubilized AX (AS-AX) fractions with different A/X ratio, on the one hand, and glycoside hydrolase family 10 and 11 endoxylanases of Aspergillus aculeatus (XAA) and Bacillus subtilis (XBS), respectively, on the other hand. AS-AX were obtained by saturated barium hydroxide treatment of hull-less barley flour water-unextractable AX. Fractionation of AS-AX by stepwise ethanol precipitation resulted in structurally different hull-less barley flour AS-AX fractions. Their A/X ratios increased with increasing ethanol concentration, and this increase in A/X ratio was reflected in their xylose substitution levels. For both XAA and XBS, the enzymic degradability of AX and apparent specific endoxylanase activity decreased with increasing A/X ratio of the AS-AX substrates, implying that both endoxylanases were sterically hindered by arabinose substituents. However, for all AS-AX fractions, hydrolysis end products of lower average degree of polymerization were obtained after incubation with XAA than with XBS, indicating that the former enzyme has a lower substrate specificity toward hull-less barley flour AS-AX than the latter. In addition, apparent specific endoxylanase activities indicated that XBS was similar to 2 times more sensitive to variations in the A/X ratio of AS-AX fractions than XAA. Furthermore, AS-AX with higher A/X ratio were relatively resistant to degradation by XBS.
ISSN: 0021-8561
Publication status: published
KU Leuven publication type: IT
Appears in Collections:Division Forest, Nature and Landscape Research
Centre for Food and Microbial Technology
× corresponding author
# (joint) last author

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