Stephens Sheida, Mahadevan Radhakrishnan, Allen D Grant
Department of Chemical Engineering and Applied Chemistry, University of Toronto, Toronto, ON, Canada.
Institute of Biomedical Engineering, University of Toronto, Toronto, ON, Canada.
Front Bioeng Biotechnol. 2021 Jan 8;8:610723. doi: 10.3389/fbioe.2020.610723. eCollection 2020.
Microbial production of chemicals using renewable feedstocks such as glucose has emerged as a green alternative to conventional chemical production processes that rely primarily on petroleum-based feedstocks. The carbon footprint of such processes can further be reduced by using engineered cells that harness solar energy to consume feedstocks traditionally considered to be wastes as their carbon sources. Photosynthetic bacteria utilize sophisticated photosystems to capture the energy from photons to generate reduction potential with such rapidity and abundance that cells often cannot use it fast enough and much of it is lost as heat and light. Engineering photosynthetic organisms could enable us to take advantage of this energy surplus by redirecting it toward the synthesis of commercially important products such as biofuels, bioplastics, commodity chemicals, and terpenoids. In this work, we review photosynthetic pathways in aerobic and anaerobic bacteria to better understand how these organisms have naturally evolved to harness solar energy. We also discuss more recent attempts at engineering both the photosystems and downstream reactions that transfer reducing power to improve target chemical production. Further, we discuss different methods for the optimization of photosynthetic bioprocess including the immobilization of cells and the optimization of light delivery. We anticipate this review will serve as an important resource for future efforts to engineer and harness photosynthetic bacteria for chemical production.
利用可再生原料（如葡萄糖）进行微生物化学品生产，已成为传统化学品生产工艺的绿色替代方案，传统工艺主要依赖石油基原料。通过使用经过工程改造的细胞，利用太阳能将传统上被视为废物的原料作为碳源来消耗，此类工艺的碳足迹可进一步降低。光合细菌利用复杂的光系统捕获光子能量，以如此快速且大量的方式产生还原电位，以至于细胞常常无法足够快地利用它，其中大部分以热和光的形式损失掉。对光合生物进行工程改造，可使我们通过将这种能量过剩导向商业上重要的产品（如生物燃料、生物塑料、大宗商品化学品和萜类化合物）的合成来加以利用。在这项工作中，我们综述了需氧和厌氧细菌中的光合途径，以更好地理解这些生物如何自然进化以利用太阳能。我们还讨论了最近在对光系统和下游反应进行工程改造方面的尝试，这些反应传递还原力以提高目标化学品的产量。此外，我们讨论了优化光合生物过程的不同方法，包括细胞固定化和光传递优化。我们预计这篇综述将成为未来利用光合细菌进行化学品生产的工程和利用方面努力的重要资源。
