Table 1.

Representative residues and impurities in recombinant collagen.

Residues and impurities	Necessity for manufacturing	Procedures or sources	Purposes
Imidazole	Yes	Rough purification	Cleaning solution for affinity chromatography
Isopropyl Thiogalactoside, IPTG	Yes	Fermentation	Induce protein expression
Antibiotics	Yes	Seed culturing and fermentation	Inhibit non-target strains
Exogenous DNA	No	Originate from exogenous microorganisms	NA
Host cell protein	No	Secreted by microorganisms	NA
Endotoxin	No	Originate from microorganisms	NA
Heavy metals and trace elements	No	Originate from raw materials and containers	NA