The potential of Synechococcus elongatus UTEX 2973 for sugar feedstock production

Abstract

It is important to obtain abundant sugar feedstocks economically and sustainably for bio-fermentation industry, especially for producing cheap biofuels and biochemicals. Besides plant biomass, photosynthetic cyanobacteria have also been considered to be potential microbe candidates for sustainable production of carbohydrate feedstocks. As the fastest growing cyanobacterium reported so far, Synechococcus elongatus UTEX 2973 (Syn2973) might have huge potential for bioproduction. In this study, we explored the potentials of this strain as photo-bioreactors for sucrose and glycogen production. Under nitrogen-replete condition, Syn2973 could accumulate glycogen with a rate of 0.75 g L(-1) day(-1) at the exponential phase and reach a glycogen content as high as 51 % of the dry cell weight (DCW) at the stationary phase. By introducing a sucrose transporter CscB, Syn2973 was endowed with an ability to secrete over 94 % sucrose out of cells under salt stress condition. The highest extracellular sucrose productivity reached 35.5 mg L(-1) h(-1) for the Syn2973 strain expressing cscB, which contained the similar amounts of intracellular glycogen with the wild type. Potassium chloride was firstly proved to induce sucrose accumulation as well as sodium chloride in Syn2973. By semi-continuous culturing, 8.7 g L(-1) sucrose was produced by the cscB-expressing strain of Syn2973 in 21 days. These results support that Syn2973 is a promising candidate with great potential for production of sugars.

Synthetic photosynthetic consortia define interactions leading to robustness and photoproduction

“…While much research focuses on engineering cyanobacterial metabolism towards the synthesis of end products (e.g., biofuels), cyanobacteria are also under consideration for the production of carbohydrate feedstocks to support fermentative bioindustrial processes [1]. In this approach, cyanobacterial biomass is processed to provide organic carbon [2–6], or cyanobacterial cells are manipulated to secrete simple fermentable sugars [7–12]. Multiple groups have recently reported that different cyanobacterial species are capable of secreting soluble sugars in considerable quantities, and continuous production can be sustained over long time periods.…”

Cpf1 Is A Versatile Tool for CRISPR Genome Editing Across Diverse Species of Cyanobacteria

“…Carbon fixation can then be coupled to the direct conversion of CO 2 into a wide range of products. Cyanobacteria have been engineered to produce commodities such ethylene1, isoprene2, and sugars34; biofuels such as alkanes5, hydrogen6 and terpenoids7; bioplastics such as polyhydroxybutyrate8; and bioactive compounds such as pharmaceuticals9 and vitamins10. One major hurdle to engineering these production systems is the lack of precise, modern genetic tools that exist for other extensively studied prokaryotes such as Escherichia coli .…”

Cyanobacteria: Promising biocatalysts for sustainable chemical production

“…Redox balance in cyanobacteria is also a key consideration, as photosynthesis can generate an overabundance of reducing equivalents in the absence of sufficient catabolic processes, leading to stunted growth (29). Finally, it is worth considering that some cyanobacterial strains may be better equipped to produce certain types of metabolites due to differences in intracellular metabolite pools or cell physiology (23,(29)(30)(31).…”

“…Typically, between 5-15% of the fixed carbon is stored via this pathway with the glycogen content reaching 50% under certain growth conditions (31,59). The diurnal lifestyle then mandates that the stored chemical energy is utilized during dark periods akin to that during heterotrophic growth.…”

“…Additionally, freshwater cyanobacteria naturally accumulate intracellular sucrose as an osmoregulator when exposed to salt stress (60). This property has been utilized to induce sugar excretion by integrating transporters and exposing cells to high salt conditions (31,42,61). This results in considerable accumulation of sugars in the growth medium.…”