Modifying the Cyanobacterial Metabolism as a Key to Efficient Biopolymer Production in Photosynthetic Microorganisms.

Maciej Ciebiada,Katarzyna Kubiak,Maurycy Daroch

doi:10.3390/ijms21197204

Maciej Ciebiada, Katarzyna Kubiak + Show 1 more

Open Access

https://doi.org/10.3390/ijms21197204

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Abstract

Cyanobacteria are photoautotrophic bacteria commonly found in the natural environment. Due to the ecological benefits associated with the assimilation of carbon dioxide from the atmosphere and utilization of light energy, they are attractive hosts in a growing number of biotechnological processes. Biopolymer production is arguably one of the most critical areas where the transition from fossil-derived chemistry to renewable chemistry is needed. Cyanobacteria can produce several polymeric compounds with high applicability such as glycogen, polyhydroxyalkanoates, or extracellular polymeric substances. These important biopolymers are synthesized using precursors derived from central carbon metabolism, including the tricarboxylic acid cycle. Due to their unique metabolic properties, i.e., light harvesting and carbon fixation, the molecular and genetic aspects of polymer biosynthesis and their relationship with central carbon metabolism are somehow different from those found in heterotrophic microorganisms. A greater understanding of the processes involved in cyanobacterial metabolism is still required to produce these molecules more efficiently. This review presents the current state of the art in the engineering of cyanobacterial metabolism for the efficient production of these biopolymers.

Highlights

Cyanobacteria are single-celled or filamentous organisms belonging to the kingdom of Prokaryotes that are capable of oxygenic photosynthesis
Cyanobacteria, photosynthetic microorganisms that utilize light as an energy source and carbon dioxide as a primary carbon source are promising microbial cell factories for sustainable production of many biochemicals including biopolymers. These properties give a promise of sustainable production of essential biopolymers directly from CO2, bypassing the need for an intermediate carbohydrate platform and resultant carbon losses associated with respiratory metabolism of heterotrophic microbial cell factories
The developments in genetic engineering and synthetic biology of cyanobacteria enable a deeper understanding of their metabolic processes responsible for biopolymer synthesis, dissection of biosynthetic mechanisms and optimization of their production so they could match the needs of growing biopolymer industry

Summary

Introduction

Cyanobacteria are single-celled or filamentous organisms belonging to the kingdom of Prokaryotes that are capable of oxygenic photosynthesis Model strains such as freshwater Synechococcus elongatus PCC 7942 (S. elongatus PCC 7942), Synechocystis PCC 6803 A thorough understanding of the influence of environmental conditions such as the availability of chemical elements, temperature, and lighting, as well as the regulation of gene expression and enzymatic activities, facilitates the creation of commercially viable strains. Some of these polymers can be already economically produced by heterotrophic microorganisms. Research aiming at the development of potentially commercially profitable strains that produce glycogen, polyhydroxyalkanoates, and extracellular polymeric substances will be discussed

Photosynthesis

Unusual TCA Cycle as a Source of Key Biopolymer Intermediates

Glycogen and Carbon Storage in Cyanobacteria

Production of PHA in Cyanobacteria

Findings

Conclusions