Photoautotrophic production of renewable ethylene by engineered cyanobacteria: Steering the cell metabolism towards biotechnological use

Abstract

Ethylene is a volatile hydrocarbon with a massive global market in the plastic industry.The ethylene now used for commercial applications is produced exclusively from nonrenewable petroleum sources, while competitive biotechnological production systems do not yet exist. This review focuses on the currently developed photoautotrophic bioproduction strategies that enable direct solar-driven conversion of CO 2 into ethylene, based on the use of genetically engineered photosynthetic cyanobacteria expressing heterologous ethylene forming enzyme (EFE) from Pseudomonas syringae. The emphasis is on the different engineering strategies to express EFE and to direct the cellular carbon flux towards the primary metabolite 2-oxoglutarate, highlighting associated metabolic constraints, and technical considerations on cultivation strategies and conditional parameters. While the research field has progressed towards more robust strains with better production profiles, and deeper understanding of the associated metabolic limitations, it is clear that there is room for significant improvement to reach industrial relevance. At the same time, existing information and the development of synthetic biology tools for engineering cyanobacteria open new possibilities for improving the prospects for the sustainable production of renewable ethylene.

Making Persistent Plastics Degradable

“…[9,52] In case of linear mono-olefins, the complete ISOMET using ethylene (in excess) as cross-coupling agent theoretically ends up in propylene [53] as the only end product independently of the double bond's position and the length of the hydrocarbon chain (Scheme 2). ISOMET reactions using renewable-based ethylene [54,55] is an emerging approach to develop sustainable, environmentally benign chemical procedures.…”

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

“…phaseolicola PK2 into S. elongatus PCC 7942 ( Fukuda et al, 1994 ). Since then, metabolic engineering and synthetic biology of cyanobacteria greatly advanced photoautotrophic ethylene production as recently reviewed by Kallio et al (2021) . Regarding amino acid hydroxylation with high potential in food and pharmaceutical industries, the work of Brandenburg et al (2021) describes the first successful example of photosynthetic hyp production directly from CO 2 , by genetic engineering of the cyanobacterium Synechocystis sp.…”

Can an external electric field switch between ethylene formation and l-arginine hydroxylation in the ethylene forming enzyme?

“…10,11 Although enzyme catalysis by EFE releases CO 2 during the reaction, this level of CO 2 production is less than the amount of greenhouse gas released in the industrial processes, and it can be further reduced by expressing EFE in a cyanobacterium which allows for light-driven CO 2 fixation. 15–18…”

“…10,11 Although enzyme catalysis by EFE releases CO 2 during the reaction, this level of CO 2 production is less than the amount of greenhouse gas released in the industrial processes, and it can be further reduced by expressing EFE in a cyanobacterium which allows for light-driven CO 2 fixation. [15][16][17][18] Previous experimental and computational studies of the reaction mechanism of EFE have demonstrated that its two reactions diverge during the reaction of iron-bound superoxide with 2OG (Scheme 1). 12,[19][20][21] As seen in other 2OG-dependent enzymes, the L-Arg hydroxylation pathway proceeds through an attack of superoxide on 2OG, leading to decarboxylation and forming a Fe(II)-succinyl-peroxide intermediate.…”