phaffii

Phaffii refers to the yeast species Komagataella phaffii, a methylotrophic member of the Saccharomycetaceae that is widely used as a host organism for recombinant protein production. The current accepted name is Komagataella phaffii; in older literature the organism was classified as Pichia pastoris, with Pichia pastoris or related synonyms still appearing in historical references.

Biology and use as an expression host. Komagataella phaffii grows to high cell densities in defined media and can utilize methanol as a carbon source. This property underpins the methanol-inducible expression system driven by the AOX1 promoter, enabling strong, tightly regulated production of recombinant proteins. Proteins can be secreted into the culture medium using signal peptides or expressed intracellularly, facilitating downstream processing. Its fermentation workflows are well established in academia and industry, and a variety of genetic tools exist for chromosomal integration and selectable markers.

Glycosylation and engineering. As a yeast system, phaffii typically adds complex N-linked glycans with yeast-type patterns. This can affect therapeutic proteins, but glycoengineering efforts have produced strains with human-like or otherwise customized glycosylation profiles, expanding its suitability for certain biopharmaceutical applications.

Applications and safety. Phaffii is widely used to produce enzymes, biocatalysts, and a range of recombinant proteins, including research-grade proteins and some therapeutic candidates. Non-pathogenic strains used in laboratories are generally regarded as safe, typically handled under standard BSL-1 conditions.