Table 1.

Basic characteristics of different host systems for the expression of recombinant proteins

Characteristics	Escherichia coli	Pichia pastoris	CHO cell
Doubling time	30 min	60–120 min	24 hr
Cost of growth medium	Low	Low	High
Complexity of growth medium	Minimum	Minimum	Complex
Expression level	High	Low to high	Low to moderate
Extracellular expression	Secretion to periplasm	Secretion to medium	Secretion to medium
Protein folding	Refolding usually required	Refolding may be required	Proper folding
N‐linked glycosylation	None	High mannose	Complex
O‐linked glycosylation	No	Yes	Yes
Phosphorylation & acetylation	No	Yes	Yes
Drawback	Accumulation of LPS	Codon bias	Contamination with animal viruses

Abbreviations: CHO, Chinese hamster ovary; LPS, lipopolysaccharide.