An assessment of the usefulness of the cyanobacterium Synechococcus subsalsus as a source of biomass for biofuel production

Abstract

ABSTRACT. Nowadays algal biofuels are considered one of the most promising solutions of global energy crisis and climate change for the years to come. By manipulation of the culture conditions, many algal species can be induced to accumulate high concentrations of particular biomolecules and can be directed to the desired output for each fuel. In this context, the present study involved the assessment of the effects of CO 2 availability and nitrogen starvation on growth and chemical composition of the cyanobacterium Synechococcus subsalsus, testing a fast-growing native strain. The control experiments were performed with Conway culture medium in 12-day batch cultures, in 6-liter flasks and 12 h photoperiod, with addition of 2 L min -1 filtered air to each flask. Other two experimental conditions were also tested: (i) the placement into the cultures of additional dissolved nutrients except nitrogen, one week after the start of growth (N-), and (ii) the input of pure CO 2 into the flasks from the 5 th day of growth (C+). In all cultures, daily cell counts were done throughout the cultivation, as well as measurements of pH and cell biovolumes. Maximum cell yield were found in N-experiments, while cell yields of C+ and control were similar. Dissolved nitrogen was exhausted before the end of the experiments, but dissolved phosphorus was not totally consumed. Protein and chlorophyll-a concentrations decreased from the exponential to the stationary growth phase of all experiments, except for protein in the control. In all experiments, carbohydrate, lipid and total carotenoid increased from the exponential to the stationary growth phase, as an effect of nitrogen limitation. Increments in carbohydrate concentrations were remarkable, achieving more than 42% of the dry weight (dw), but concentrations of lipid were always lower than 13% dw. The addition of pure CO 2 did not cause a significant increase in biomass of S. subsalsus nor generated more lipid and carbohydrate than the other treatments. Nitrogen starvation caused an intense accumulation of carbohydrate, but the increments of lipid were small. Despite the fast growth, the cyanobacterium S. subsalsus has a virtually null potential for biodiesel production, given its low lipid concentrations. The high concentrations of carbohydrate combined with fast growth point to the potential use of this species as raw material for other possible biotechnological processes, after a demonstration of technical and economic viability. Keywords: biodiesel, biomass, cultivation, lipid, microalgae, cyanobacteria, productivity.Evaluación de la utilidad de la cianobacteria marina Synechococcus subsalsus como fuente de biomasa para la producción de biocombustibles RESUMEN. Actualmente los biocombustibles elaborados con algas se consideran una de las soluciones más prometedoras de la crisis energética mundial y el cambio climático para los años venideros. Mediante la manipulación de las condiciones de cultivo, muchas especies de algas pueden ser inducidas para acumular altas concentracione...

Cyanobacteria as an eco‐friendly resource for biofuel production: A critical review

“…Neutral lipids contents were increased by the stressors in both of the strains, which could be valuable for the lipid‐based biodiesel generation . The effect of CO 2 and nitrogen sources on the growth and lipid synthesis of Synechococcus subsalsus , a fast‐growing cyanobacterium, was investigated by Setta et al The cyanobacterium was cultured in seawater, enriched with Conway medium. They found that the S. subsalsus is not a notable candidate for biofuel generation, due to its low lipid accumulation .…”

“…The effect of CO 2 and nitrogen sources on the growth and lipid synthesis of Synechococcus subsalsus , a fast‐growing cyanobacterium, was investigated by Setta et al The cyanobacterium was cultured in seawater, enriched with Conway medium. They found that the S. subsalsus is not a notable candidate for biofuel generation, due to its low lipid accumulation . The conversion of glycogen to ethanol, using saccharification and fermentation methods, causes special attention to this primary feedstock.…”

“…They found that the S. subsalsus is not a notable candidate for biofuel generation, due to its low lipid accumulation. 61 The conversion of glycogen to ethanol, using saccharification and fermentation methods, causes special attention to this primary feedstock. Synechococcus sp.…”

Bioproduct Potential of Outdoor Cultures of Tolypothrix sp.: Effect of Carbon Dioxide and Metal-Rich Wastewater

“…Furthermore, the produced biomass has multiple commercial applications through bioproduct development. In general, potential algal bioproducts include medicinal compounds, food and feed supplements (restricted to CO 2 enriched grown species without inclusion of metal-or other potentially toxic compoundcontaining wastewater treatment), pigments (e.g., β-carotene, astaxanthin, fucoxanthin, lutein, phycocyanin, phycoerythrin, the latter two from cyanobacteria), protein, carbohydrate, biofuel and biohydrogen, and biofertilizers (Setta et al, 2017;von Alvensleben and Heimann, 2019). Specific cyanobacterial bioproducts could be protein, mineral and unsaturated fatty acid supplements and the pigments phycocyanin and phycoerythrin from Arthrospira platensis or Limnospira maxima (formerly Spirulina platensis and S. maxima), where the protein content of the biomass can reach 74% (Cohen, 1997), which can be extracted through biorefining (Borowitzka, 2013).…”

Optimization of biomass and some metabolites productivity of Merismopedia tenuissima and Spirulina (Arthrospira) platensis grown under stress conditions

“…PCC7942 has recorded an enhancement through increasing salinity concentration (Verma et al, 2019). Setta et al (2014) reported that the carbohydrate content was enhanced by more than 42% of dry weight under a nitrogen-free medium in Synechococcus subsalsus. The current study targeted isolating some cyanobacteria species from lakes and freshwater bodies of Assiut Governorate in Upper Egypt, and estimating the effects of manipulating the concentrations of phosphorus, nitrogen, and sodium chloride as well as different pH values on the biomass productivity and productivities of some metabolites of S. platensis and M. tenuissima.…”