Using DNA-tagged mutagenesis to improve heterologous protein production in Aspergillus oryzae

Using DNA-tagged mutagenesis to improve heterologous protein production in Aspergillus oryzae. Fungal Genetics and Biology 29, 28-37. Restriction enzyme-mediated integration (REMI) has been employed as a mutagen to generate two insertion libraries in an Aspergillus oryzae strain expressing a Thermomyces lanuginosus lipase. The REMI libraries were created using linearized plasmid containing the A. oryzae pyrG and either BamHI or EcoRI enzyme. The libraries were screened for lipase production, and mutants with increased production were isolated. The genomic DNA flanking the integration event was cloned from one of the mutants with increased lipase titers (DEBY10.3). Nucleotide sequence of the flanking DNA revealed similarity to the Aspergillus nidulans palB gene. Disruption of the palB gene in a strain producing lipase resulted in increased lipase expression. Additionally, complementation of the palB phenotype of DEBY10.3 led to a decrease in lipase production. These lines of evidence demonstrate that the increase in lipase yield in DEBY10.3 is linked to the palB phenotype generated by the integration of the pyrG gene into the palB gene. The results also demonstrated that tagged mutagenesis with REMI can be used to identify genes that influence expression of heterologous proteins.