CLONING OF THE ASPERGILLUS-NIGER GENE ENCODING ALPHA-L-ARABINOFURANOSIDASE-A

Using L-arabitol as an inducer, simple induction conditions were estab lished that resulted in high-level expression of alpha-L-arabinofurano sidase A by an Aspergillus niger D-xylulose kinase mutant strain. Thes e conditions were adapted to construct a cDNA expression library from which an alpha-L-arabinofuranosidase A cDNA clone was isolated using s pecific antiserum. The corresponding gene encoding alpha-L-arabinofura nosidase A (abfA) was isolated from a genomic library and cloned into a high copy plasmid vector. By co-transformation of uridine auxotrophi c mutants lacking orotidine-5-phosphate decarboxylase activity, the af bA gene was introduced both in A. niger and A. nidulans, using the A. niger pyrA gene as selection marker. The identity of the abfA gene was confirmed by overexpression of the gene product by A. niger and A. ni dulans transformants, upon growth using sugar beet pulp as the carbon source.