Yeast expression system, especially Pichia pastoris (P. pastoris), has a number of advantages over other expression systems for the production of recombinant protein and antibody. It is ease of genetic manipulation, has low cost for high protein production, and can perform higher eukaryotic protein modifications, such as glycosylation, disulfide bond formation and proteolytic processing. Unlike mammalian cells, P. pastoris does not require serum in culture medium, and can be grown to very high cell densities using minimal media. The fermentation processes can be readily scaled up to meet greater demands, and the integrated vectors have genetic stability in continuous and large-scale fermentation. Although P. pastoris can perform N-glycosylation modification, it is also a serious disadvantage of P. pastoris to express glycoprotein. Protein N-glycosylation in P. pastoris has glycans of the high mannose type with up to 100 or more mannose residues (hypermannosylation), which differ significantly from those of mammalian cells, and alter protein structure and function

Genekine has genetically re-engineered N-glycosylation modification in P. pastoris to mimic N-glycosylation modification in mammalian cells. By deleting the intrinsic N-glycosylation genes and integrating mammalian N-glycosylation genes in the genome of P. pastoris, we have constructed glycoengineered P. pastoris strains, which yield human-like N-glycans on protein and antibody. Since the hypermannosylation of N-glycosylation is eliminated, our glycoengineered P. pastoris offer substantial advantages over P. pastoris and other expression systems to produce high level of protein and antibody for both basic research and industrial manufacture.