A recombinant filamentous fungal cell (e.g. Aspergillus) having one or more inactivated chromosomal genes is provided. The chromosomal genes in some embodiments correspond to derA, derB, htmA, mnn9, mnn10, ochA, dpp4, dpp5, pepAa, pepAb, pepAc, pepAd, pepF and combinations thereof. The recombinant fungal cells may include further inactivated chromosomal genes which correspond to pepA, pepB, pepC and pepD. The recombinant filamentous fungal cells may include a heterologous nucleic acid encoding a protein of interest. Also provided are methods of producing a protein of interest in said recombinant filamentous fungal cell.