Mutation of a Conserved Alanine Residue in Transcription Factor AraR Leads to Hyperproduction of α-l-Arabinofuranosidases in Penicillium oxalicum

α- l -Arabinofuranosidases are important in the degradation of plant polysaccharides and are used in several industrial processes. Although the use of filamentous fungi for the production of α- l -arabinofuranosidases is widely reported, there are few reports on strain engineering for enhanced production of these enzymes by fungi. In this study, the function of transcription factor AraR in l -arabinose release and catabolism by the fungus Penicillium oxalicum ( P. oxalicum ) is investigated. Also, a mutant of AraR, AraR A731V , is constructed to improve the production of α- l -arabinofuranosidases on the basis of the sequence homology between AraR and the xylanolytic gene activator XlnR. The AraR A731V -overexpressing strain can synthesize α- l -arabinofuranosidase in the absence of an inducer and shows a 54.1-fold increase in α- l -arabinofuranosidase production and a 7.4-fold increase in α-galactosidase production in the medium containing wheat bran. Determination of the transcript abundances of lignocellulolytic enzyme genes reveals significant upregulation of multiple α- l -arabinofuranosidase genes and downregulation of some cellulolytic and xylanolytic enzyme genes in the engineered strain relative to its parent. Taken together, the results suggest the conserved regulatory function of AraR in the family Trichocomaceae and provide a strategy for engineering fungal strains for enhanced α- l -arabinofuranosidase production. Graphical α- l -Arabinofuranosidases are important in plant cell-wall degradation and are used in many industries. In this study, it is shown that a point mutation of transcription factor AraR could increase α- l -arabinofuranosidase production by 54.1-fold in the fungus Penicillium oxalicum .