Loss of function of the carbon catabolite repressor CreA leads to low but inducer independent expression of the ferulic acid esterase B gene in Aspergillus niger

The faeB gene of Aspergillus niger encodes a feruloyl esterase that catalyzes the hydrolysis of ester bonds between hydroxycinnamic acids (e.g. ferulic acid) and plant-polysaccharides, thereby releasing the hydroxycinnamic acids. With the aim to decipher the mechanisms involved in the transcriptional regulation of faeB, a genetic screen was performed to isolate A. niger mutants displaying inducer independent expression of faeB. We constructed PfaeB-amdS and PfaeB-lux dual reporter strains and isolated trans-acting mutants in which both reporters were induced, based on growth on acetamide plates and induced luciferase activity respectively. The genetic screen yielded over 111 trans-acting mutants. The genome of one the mutants was sequenced and revealed a point mutation in the creA gene.