title: Disruption of the L-arabitol dehydrogenase encoding gene in Aspergillus tubingensis results in increased xylanase production.
abstract: Fungal xylanases are of major importance to many industrial sectors, such as food and feed, paper and pulp, and biofuels. Improving their production is therefore highly relevant. We determined the molecular basis of an improved xylanase-producing strain of Aspergillus tubingensis that was generated by UV mutagenesis in an industrial strain improvement program. Using enzyme assays, gene expression, sequencing of the ladA locus in the parent and mutant, and complementation of the mutation, we were able to show that improved xylanase production was mainly caused by a chromosomal translocation that occurred between a subtilisin-like protease pepD gene and the L-arabitol dehydrogenase encoding gene (ladA), which is part of the L-arabinose catabolic pathway. This genomic rearrangement resulted in disruption of both genes and, as a consequence, the inability of the mutant to use L-arabinose as a carbon source, while growth on D-xylose was unaffected. Complementation with constitutively expressed ladA confirmed that the xylanase overproducing phenotype was mainly caused by loss of ladA function, while a knockout of xlnR in the UV mutant demonstrated that improved xylanase production was mediated by XlnR. This study demonstrates the potential of metabolic manipulation for increased production of fungal enzymes.
authors.affiliation: Danisco Innovation, Denmark.
authors.forename: Igor
authors.initials: I
authors.lastname: Nikolaev
authors.forename: Sara
authors.initials: S
authors.lastname: Farmer Hansen
authors.forename: Susan
authors.initials: S
authors.lastname: Madrid
authors.forename: Ronald P
authors.initials: RP
authors.lastname: de Vries
mesh_terms: D001230:Aspergillus / Q000201:enzymology* / Q000235:genetics* / Q000378:metabolism / Q000528:radiation effects; D043364:Endo-1,4-beta Xylanases / Q000235:genetics / Q000378:metabolism; D005656:Fungal Proteins / Q000235:genetics* / Q000378:metabolism; D005800:Genes, Fungal / Q000528:radiation effects; D016296:Mutagenesis / Q000528:radiation effects; D009154:Mutation / Q000528:radiation effects*; D013237:Stereoisomerism; D013401:Sugar Alcohol Dehydrogenases / Q000235:genetics* / Q000378:metabolism; D013402:Sugar Alcohols / Q000378:metabolism*; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism; D014178:Translocation, Genetic; D014466:Ultraviolet Rays
chemical_list: D005656:Fungal Proteins; D013402:Sugar Alcohols; D015534:Trans-Activators; C115443:XlnR protein, Aspergillus; D013401:Sugar Alcohol Dehydrogenases; D043364:Endo-1,4-beta Xylanases; C014999:arabitol
keywords: Aspergillus tubingensis; L-Arabitol dehydrogenase; Pentose catabolic pathway; XlnR; Xylanase production