Affiliation: CBS-KNAW Fungal Biodiversity Centre, Uppsalalaan 8, 3584 CT Utrecht, The Netherlands.
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.