BACKGROUND: Komagataella phaffii (K. phaffii) is used to manufacture biologic medicines, food proteins, reagents, and materials. Despite its increasing prevalence, further improvements to its productivity would enhance its economic and operational benefits. Genomic engineering represents one approach to increase its cell-specific productivity. We hypothesized that combining the metrics for the relative essentiality of genes with biological inference for relevance to protein secretion could identify genes that, when disrupted, would improve specific productivity in the resulting strains.
RESULTS: The essentiality of genes in K. phaffii (NRRL Y-11430) were predicted through a genome-wide knockout screen using CRISPR-Cas9. Based on the results from this screen, we selected and subsequently disrupted the least essential genes from two gene groups heavily associated with secretion, namely those relating to the cell wall and vacuolar transport. Strains of K. phaffii with single gene disruptions from these gene sets showed significantly improved production of a monoclonal antibody (mAb). These strains exhibited no discernible differences in growth or apparent profiles of host cell proteins when compared to the parental strain. The best-performing strains consistently showed 2-3x enhancements in specific productivity and titers across scales (3-150 mL), culture formats (plates, flasks, bioreactors), and processing operations (batch and fed-batch).
CONCLUSIONS: This study demonstrates how combining data on gene essentiality and prior knowledge of biological pathways related to a phenotypic trait of interest (here protein secretion) can inform strain engineering to enhance the trait. This study expands the catalog of genetically engineered strains of K. phaffii with improved productivity. These strains support the long-term goal of achieving low-cost, high-volume production of recombinant proteins using this host. Further engineering of these strains and optimization of fermentation processes could enable volumetric productivities comparable to those of other established hosts used to produce mAbs and other complex recombinant proteins.
