Abstract: The present invention relates to novel engineered lower eukaryotic host cells for expressing heterologous proteins and to methods of generating such strains.

Abstract: The present invention relates to novel engineered lower eukaryotic host cells for expressing heterologous proteins and to methods of generating such strains.

Abstract: Lower eukaryote host cells in which expression of the endogenous protein mannosyltransferase 2 (PMT2) gene has been disrupted by introducing a nucleic acid molecule encoding a Pmt2p protein having a mutation in a conserved region of the protein. The mutation confers to the host cell resistance to PMT inhibitors, which are used to reduce the amount of O-glycosylation of recombinant proteins produced by the host cells but which also have the effect of reducing the robustness of the host cells during fermentation. When host cells that express the mutated PMT2 gene but not the endogenous Pmt2p are cultivated in the presence of a P MT inhibitor, the host cells display an increase in cellular robustness during fed-batch fermentation and express recombinant pro teins in high yield while the amounts O-glycosylation are similar to that produced under similar conditions by host cells that express only the endogenous P MT2 gene.