Sink Engineering in Photosynthetic Microbes

Santos-Merino, María; Singh, Amit Kumar; Ducat, Daniel C.

doi:10.1002/9783527824908.ch6

Cited by 7 publications

(2 citation statements)

References 203 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The latter observation is correlated with an increase in Rubisco abundance that was revealed by proteomic analysis >24 h following induction of sucrose export, and a concomitant increase in carboxysome number ( Singh et al, 2022 ). While the mechanisms underlying these changes in photosynthetic performance are not well understood, it has been hypothesized that they arise from a relaxation in “sink limitations” on photosynthesis that can arise when the downstream consumption of products of photosynthesis (e.g., ATP, NADPH, CBB outputs) is insufficient to keep up with the supply ( Santos-Merino et al, 2021a ). Stated differently, when carbon fixation is not the rate-limiting step of cell metabolism (e.g., under enriched CO 2 atmospheres commonly used in laboratory conditions), the expression of a heterologous pathway may act as an additional “sink” and bypass downstream limitations of cell growth and division.…”

Section: Engineering Cyanobacteria To Produce Sucrosementioning

confidence: 99%

Cyanobacteria as cell factories for the photosynthetic production of sucrose

2023

View full text Add to dashboard Cite

Biofuels and other biologically manufactured sustainable goods are growing in popularity and demand. Carbohydrate feedstocks required for industrial fermentation processes have traditionally been supplied by plant biomass, but the large quantities required to produce replacement commodity products may prevent the long-term feasibility of this approach without alternative strategies to produce sugar feedstocks. Cyanobacteria are under consideration as potential candidates for sustainable production of carbohydrate feedstocks, with potentially lower land and water requirements relative to plants. Several cyanobacterial strains have been genetically engineered to export significant quantities of sugars, especially sucrose. Sucrose is not only naturally synthesized and accumulated by cyanobacteria as a compatible solute to tolerate high salt environments, but also an easily fermentable disaccharide used by many heterotrophic bacteria as a carbon source. In this review, we provide a comprehensive summary of the current knowledge of the endogenous cyanobacterial sucrose synthesis and degradation pathways. We also summarize genetic modifications that have been found to increase sucrose production and secretion. Finally, we consider the current state of synthetic microbial consortia that rely on sugar-secreting cyanobacterial strains, which are co-cultivated alongside heterotrophic microbes able to directly convert the sugars into higher-value compounds (e.g., polyhydroxybutyrates, 3-hydroxypropionic acid, or dyes) in a single-pot reaction. We summarize recent advances reported in such cyanobacteria/heterotroph co-cultivation strategies and provide a perspective on future developments that are likely required to realize their bioindustrial potential.

show abstract

Section: Engineering Cyanobacteria To Produce Sucrosementioning

confidence: 99%

Cyanobacteria as cell factories for the photosynthetic production of sucrose

2023

View full text Add to dashboard Cite

show abstract

“…On the contrary, a single overexpression of pyk was found to increase the total carbon productivity. This photosynthetic enhancement is considered to be a phenomenon that occurs when expressing and increasing the sink metabolism; however, the precise mechanisms remain unknown (Santos-Merino et al, 2021).…”

Section: Discussionmentioning

confidence: 99%

Minimized dark cataplerosis of the Calvin cycle ensures prompt photosynthetic initiation in cyanobacteria

Tanaka,

Kondo,

Hasunuma

2023

Preprint

View full text Add to dashboard Cite

As primary contributors to oxygenic photosynthesis, cyanobacteria intricately regulate their metabolic pathways during the diurnal cycle to ensure survival and growth. Under dark conditions, breakdown of stored energy reserves of glycogen replenishes the intermediates, especially the downstream glycolytic metabolites necessary for photosynthetic initiation upon light irradiation. The intracellular level of the intermediates is maintained throughout the dark period. However, it remains unclear how their accumulation is maintained in the dark despite the limited availability of glycogen. Here, we showed that the metabolite accumulation stability is ensured by the low activities of phosphoenolpyruvate (PEP) converting enzymes, namely PEP carboxylase and pyruvate kinase, during the dark period. Overexpression of these enzymes significantly decreased the accumulation of glycolytic intermediates after dark incubation. The oxygen evolution ability simultaneously decreased in the overexpressing strains, indicating that the dark limitation of the PEP-consuming pathway facilitates photosynthetic initiation through the maintenance of glycolytic intermediates. This finding shed light on the importance of controlling cataplerotic flux during the dark for maintaining stable operation of the Calvin cycle.

show abstract