Overexpression of XlnR Regulated Hemicellulase-Encoding Genes in Aspergillus vadensis
Ronald P. de Vries.
Aspergillus vadensis is a close relative of Aspergillus niger and is particularly interesting for hemicellulase
production as it does not produce extracellular proteases. The main regulator driving hemicellulase production in
Aspergilli and other fungi is XlnR and overexpression of this regulator leads to increased hemicellulase levels in some
species. To increase hemicellulase production in A. vadensis strains were generated that contain multiple copies of two
XlnR target genes, xlnD and faeA, encoding β-xylosidase and feruloyl esterase A respectively, and/or multiple copies of
xlnR. The strains were compared with respect to β-xylosidase and feruloyl esterase activity, respectively, to determine the
effect of overexpression of xlnR in comparison to overexpression of the target genes (faeA, xlnD). The results demonstrate
that insertion of additional copies of faeA and xlnD had a much larger effect on the corresponding activities than
additional copies of xlnR in A. vadensis, suggesting that the amount of XlnR present in A. vadensis is sufficient to activate
additional copies of the target genes without much effect on the production of other XlnR-regulated activities.
Keywords: Aspergillus niger, Aspergillus vadensis, hemicellulases, heterologous protein production, regulator XlnR, feruloyl
esterase A, β-xylosidase.
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