Table 1. Comparison of various cell-free protein synthesis systems.

Type	Advantages	Disadvantages
E.coli S30 extract	Simple and cost-effective preparation of extract High protein synthesis yield High rate of protein synthesis Clearly elucidated biochemical knowledge and well established tools for genetic modifications Low-cost energy sources Able to fold complex proteins	Lack of post-translational modifications No eukaryotic-specific modifications
Wheat-germ extract	Wide-spectrum expression of eukaryotic proteins has been achieved repeatedly High yield of complex proteins Sophisticated high-throughput method for proteomics	Low yield of extract from cells Special washing procedure of wheat germ is needed Poor genetic modification tools
Rabbit reticulocyte	Easy cell breakage and quick preparation of extract Eukaryotic-specific modifications High protein yield of hemoglobin protein while moderate/low yields for other proteins	Complex manipulation of animal tissue required Narrow spectrum of proteins expressed to date High background of endogenous globin mRNAs and abundance of RNase M Poor genetic modification tools Low protein synthesis yields
Insect cell extract	Easy cell breakage and quick preparation of extract Various eukaryotic-specific modifications Signal sequence processing	Cell cultivation is expensive and time-consuming Poor genetic modification tools
Yeast	Low-cost and scalable cultivation Clearly elucidated biochemical knowledge and well established tools for genetic modifications Some eukaryotic-specific modifications	Rigid cell wall made from various polysaccharides makes lysis more difficult High abundance of various ATPases and phosphatases in some organelles Low protein synthesis yield

^*Batch system