The present invention provides genetically modified
Pichia strains wherein at least one
nucleic acid sequence encoding a functional
gene product and / or at least one
nucleic acid sequence necessary for expression of at least one functional
gene product in said
Pichia strain is genetically modified, wherein said
gene product is responsible for
proteolysis and / or
glycosylation in said genetically modified
Pichia strain. In particular, Pichia strains are provided wherein
nucleic acid sequence encoding a functional
gene product or expression of said
gene product are genetically modified: PEP4, PRB1, YPS1, YPS2, YMP1, YMP2, YMP3 and PMT4. Also provided herein are genetically modified host cells wherein
wild type parent of said genetically modified host
cell comprises a gene encoding a polypeptide having at least 60%
sequence identity to amino acids 1-865 of SEQ ID NO:4, SEQ ID NO:6 and SEQ ID NO:8 wherein said gene is genetically modified in the
genome of said host
cell such that the
gene product is reduced or eliminated in said genetically modified host
cell compared with said
wild type host cell.