Biomanufacturing by in vitro biosystems containing complex enzyme mixtures

Microbial fermentation is the current predominant biomanufacturing platform. However, it suffers from low production yields, slow reaction rates, and scaling-up challenges. In vitro enzymatic biosystems are emerging to expand the traditional biotechnological mode by utilizing more than three enzymes for manufacturing the desired product from cheap substrate. In the past few years, numerous proofs of the concept of in vitro biosystems containing complex enzyme mixtures from different groups worldwide have inspired the development of these platforms for biomanufacturing, these biosystems show advantages such as near-theoretical product yields, faster reaction rates, reduced interference from toxic compounds, and unprecedented level of engineering. In this review, several examples of in vitro systems are presented to illustrate these advantages and possible solutions to overcome the remaining challenges are discussed. The continuing decrease in enzyme cost and improvements in enzyme engineering techniques will make in vitro biosystems a comparable biomanufacturing platform for microbial fermentation in the near future.