Engineering Photosynthetic Bioprocesses for Sustainable Chemical Production: A Review

Abstract

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.

Exploitation of Hetero- and Phototrophic Metabolic Modules for Redox-Intensive Whole-Cell Biocatalysis

“…Respective processes are often hindered by light limitation, inefficient light utilization, low biomass concentrations, and low production rates. As light supply is a key aspect and a major limiting factor for high-density cultivation of phototrophs, measures are needed to improve light supply and utilization ( Stephens et al, 2021 ). Major factors are the limited absorption capacities and self-shading effects in outdoor applications ( Socher et al, 2016 ).…”

Application of biocompost enriched with arbuscular mycorrhizae for the growth of Allium cepa L.

“…Besides that, the absorption of water and nutrients is also carried out by external hyphae of AM. According to Shrestha et al (2020) and Savarino et al (2021), N as macronutrient function to stimulate plant growth, assimilate produced through the photosynthesis process are a source of energy for plants to carry out further metabolic processes (Walker et al, 2020;Stephens et al, 2021), which also a source of energy for AM as a form of mutualistic symbiosis between plants and mycorrhizae (Sugiura et al, 2020;Yu et al, 2020). Besides that, the photosynthesis product in the form of assimilate constitute the source of energy used for three activities, namely: (1) for plant growth (Ajdanian et al, 2020;Yavari et al, 2021), (2) stored as food reserves (Siahpoosh, 2014;Aluko et al, 2021), and (3) stored as a sink which is a form of plant economic yield (Arifin et al, 2019;Sales et al, 2021).…”

SEVA-Cpf1, a CRISPR-Cas12a vector for genome editing in cyanobacteria

“…Synechococcus PCC 11,801 and PCC 11,901 (hereafter, Synechococcus 11,801 and Synechococcus 11,901) are also becoming popular for biotechnological purposes [ 4 , 5 ]. To date, cyanobacteria have been exploited to convert CO 2 into a wide range of valuable products, for instance: biofuels [ 6 , 7 ]; commercial terpenoids [ 8 , 9 ]; polymeric compounds useful for bioplastic materials [ 10 ]; bioactive compounds and vitamins [ 11 ]; sugars [ 12 ]; and pigments with potent antioxidant activity [ 13 ]. To enable metabolic engineering in the different cyanobacterial strains, advanced genetic tools are emerging, from conventional methodologies to innovations in gene expression, genome editing and regulation systems [ 14 – 19 ].…”