Cell-free system

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A cell-free system is an in vitro tool widely used to study biological reactions that happen within cells while reducing the complex interactions found in a whole cell. Subcellular fractions can be isolated by ultracentrifugation to provide molecular machinery that can be used in reactions in the absence of many of the other cellular components.

Cell-free biosystems can be prepared by mixing a number of purified enzymes and coenzymes. Cell-free biosystems are proposed as a new low-cost biomanufacturing platform compared to microbial fermentation used for thousands of years. Cell-free biosystems have several advantages suitable in industrial applications:[1][2]

  1. In vitro biosystems can be easily controlled and accessed without membranes. Cell-free protein synthesis is becoming a new alternative choice for fast protein synthesis.
  2. Very high product yields are usually accomplished without the formation of by-products or the synthesis of cell mass. For example, nearly 12 H2 has been produced per glucose unit of polysaccharides and water, three times of the theoretical yield of the best anaerobic hydrogen-producing microorganisms.[3]
  3. In vitro biosystems can implement some biological reactions that living microbes or chemical catalysts cannot implement before. For example, beta-1,4-glucosidic bond linked cellulose can be converted to alpha-1,4-glucosidic bond linked starch by a mixture of intracellular and extracellular enzymes in one pot.[4]
  4. Enzymatic systems, without the barrier of cellular membrane, usually have faster reaction rates than microbial systems. For instance, enzymatic fuel cells usually have much higher power outputs than microbial fuel cells.[5]
  5. Enzyme cocktails can tolerate toxic compounds better than microorganisms.[6]
  6. Enzyme mixtures usually work under broad reaction conditions, such as high temperature, low pH, the presence of organic solvents or ionic liquids.


  1. ^ Y. H. Percival Zhang (March 2010). "Production of biocommodities and bioelectricity by cell-free synthetic enzymatic pathway biotransformations: Challenges and opportunities". Biotechnology and Bioengineering. 105 (4): 663–677. PMID 19998281. doi:10.1002/bit.22630. 
  2. ^ "New biotechnology paradigm: cell-free biosystems for biomanufacturing". Green Chemistry. 15: 1708. doi:10.1039/C3GC40625C. 
  3. ^ Zhang YH, Evans BR, Mielenz JR, Hopkins RC, Adams MW (2007). "High-Yield Hydrogen Production from Starch and Water by a Synthetic Enzymatic Pathway". PLoS ONE. 2: e456. PMC 1866174Freely accessible. PMID 17520015. doi:10.1371/journal.pone.0000456. 
  4. ^ You C, Chen H, Myung S, Sathitsuksanoh N, Ma H, Zhang XZ, Li J, Zhang YH. "Enzymatic transformation of nonfood biomass to starch". Proceedings of the National Academy of Sciences. 110: 7182–7187. PMC 3645547Freely accessible. PMID 23589840. doi:10.1073/pnas.1302420110. 
  5. ^ Zhu Z, Kin Tam T, Sun F, You C, Percival Zhang YH. "A high-energy-density sugar biobattery based on a synthetic enzymatic pathway". Nature Communications. 5: 3026. PMID 24445859. doi:10.1038/ncomms4026. 
  6. ^ "Biohydrogenation from Biomass Sugar Mediated by In Vitro Synthetic Enzymatic Pathways". Chemistry. 18: 372–380. doi:10.1016/j.chembiol.2010.12.019. 

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