Current Metabolic Engineering Strategies for Photosynthetic Bioproduction in Cyanobacteria

Abstract

Cyanobacteria are photosynthetic microorganisms capable of using solar energy to convert CO2 and H2O into O2 and energy-rich organic compounds, thus enabling sustainable production of a wide range of bio-products. More and more strains of cyanobacteria are identified that show great promise as cell platforms for the generation of bioproducts. However, strain development is still required to optimize their biosynthesis and increase titers for industrial applications. This review describes the most well-known, newest and most promising strains available to the community and gives an overview of current cyanobacterial biotechnology and the latest innovative strategies used for engineering cyanobacteria. We summarize advanced synthetic biology tools for modulating gene expression and their use in metabolic pathway engineering to increase the production of value-added compounds, such as terpenoids, fatty acids and sugars, to provide a go-to source for scientists starting research in cyanobacterial metabolic engineering.

Impact of irradiance and inorganic carbon availability on heterologous sucrose production in Synechococcus elongatus PCC 7942

“…Cyanobacteria are a diverse phylum of photosynthetic prokaryotes that are under consideration as an alternative carbohydrate feedstock species due to their ability to hyperaccumulate soluble sugars under certain growth conditions ( Hays and Ducat, 2015 ). Moreover, cyanobacteria are less likely to compete for land and water resources with food crops, are faster growing, relatively easier to genetically engineer, and have a higher photosynthetic efficiency than land plant sources of carbohydrate feedstocks ( Parmar et al., 2011 ; Satta et al., 2023 ). One promising approach for cyanobacterial sucrose production involves the heterologous expression of sucrose permease ( cscB ), which was originally reported to allow up to ~80% of fixed carbon to be exported in the form of sucrose when expressed in the model cyanobacterium, Synechococcus elongatus PCC 7942 ( Ducat et al., 2012 ).…”

Optimal energy and redox metabolism in the cyanobacterium Synechocystis sp. PCC 6803

“…Cyanobacteria are photosynthetic microbes that serve as an attractive platform for the sustainable production of chemicals and fuels, mainly due to their capability of converting atmospheric carbon dioxide into organic compounds by using solar energy, their relative rapid growth rate, and the readily available genetic toolbox for various species 1 . In the past years, the unicellular cyanobacterium Synechocystis sp.…”

“…In addition, re-oxidation of NAD(P)H to NAD(P) + and phosphorylation-dephosphorylation of reducing equivalents are important for balancing the ATP/NADPH budget and maintaining redox homeostasis 15 . Despite the importance of meeting the energy and redox requirement to achieve an efficient cellular performance 16 , 17 , only few metabolic engineering efforts of Synechocystis have targeted this designing strategy 18 , while most studies are concerned with controlling carbon partitioning 1 .…”