Metabolic engineering efforts that harness living organisms to produce natural products and other useful chemicals face inherent difficulties because the maintenance of life processes often runs counter to our desire to maximize important production metrics. These challenges are particularly problematic for commodity chemical manufacturing where cost is critical. A cell-free approach, where biochemical pathways are built by mixing desired enzyme activities outside of cells, can obviate problems associated with cell-based methods. Yet supplanting cell-based methods of chemical production will require the creation of self-sustaining, continuously operating systems where input biomass is converted into desired products at high yields, productivities, and titers. We call the field of designing and implementing reliable and efficient enzyme systems that replace cellular metabolism, synthetic biochemistry.

利用生命有机体生产天然产物和其他有用化学物质的代谢工程工作面临固有的困难，因为生命过程的维护常常与我们最大化重要生产指标的愿望背道而驰。这些挑战对于成本至关重要的商品化学制造尤其成问题。通过在细胞外混合所需的酶活性来建立生化途径的无细胞方法可以避免与基于细胞的方法相关的问题。然而，要取代基于细胞的化学生产方法，就需要建立一种自我维持的，连续不断的操作系统，在该系统中，输入的生物质能以高产量，高生产率和高滴度转化为所需的产品。