Improved Hemicellulase Production by Genetic Modification of Carbon Catabolite Repression and Xylanolitic Activation in Aspergillus niger

Background: Cultivation and media optimization is one way to improve hemicellulase production in Aspergillus niger, but bioprocess approaches have limitations due to the carbon catabolite repression (CCR) process. Objective: This study aimed to improve hemicellulase production by genetic modifications at CCR levels in A. niger strain. Method: Deletion of the creA gene to derepress the expression of the hemicellulolytic genes and introduction of a constitutively active version of xlnR were performed. Results and Discussion: The deletion of creA resulted in a higher expression of some hemicellulolytic genes and a higher specific enzyme production. Introduction of the constitutively active xlnR in a ΔCreA strain increased fungal biomass production, but did not result in a higher expression/production of most hemicellulases on xylose, although it was possible to double the productivity of β-xylosidase. Conclusions: A dominant effect of creA deletion on xlnR overexpression in the production of biomass degrading enzymes was present and indicated that a mechanism not totally elucidated is present and involves fungal growth and inductor.