Abstract
Conversion of biological feedstocks into value-added chemicals is mostly performed via microbial fermentation. An emerging alternative approach is the use of cell-free systems, consisting of purified enzymes and cofactors. Unfortunately, the in vivo and in vitro research communities rarely interact, which leads to oversimplifications and exaggerations that do not permit fair comparison of the two strategies and impede synergistic interactions. Here, we provide a comprehensive account for the advantages and drawbacks associated with each strategy, and further discuss recent research efforts that aim to breach the limits of cellular and cell-free production. We also explore emerging hybrid solutions that integrate the benefits of both worlds and could expand the boundaries of biosynthesis.