Spirulina sp. LEB 18 cultivation in a raceway-type bioreactor using wastewater from desalination process: Production of carbohydrate-rich biomass.

This study aimed to evaluate the biomass production of Spirulina sp. LEB 18 cultivated in wastewater from the desalination process. The outdoor cultivations (210 L) were performed using as culture medium 100% wastewater supplemented with 25% of Zarrouk constituents (Tcs). In parallel, it was performed a control assay using 100% Zarrouk constituents. The biomass production in Tcs assay (1.14 g L-1) was only 9% lower than the control assay (1.25 g L-1). The Tcs assay showed a higher content of carbohydrates (52.29%), lipids (12.79%) and ash (2.69%) compared to the control assay (47.91; 7.59 and 1.29%, respectively). The biomass from the control and Tcs assays had mostly monounsaturated fatty acids C15:1 and C18:2n6t. The Spirulina sp. LEB 18 could use efficiently the nutrients from the wastewater, showing high removal efficiency of NO3- (96.99%), PO4 (83.11%) and Z (96.43%). At the same time, high added value biomolecules were produced for different purposes.

Role of light emitting diode (LED) wavelengths on increase of protein productivity and free amino acid profile of Spirulina sp. cultures.

LEDs have specific wavelengths that can positively influence the production of microalga biomass and biomolecules of interest. Filling the gaps in the literature, this study evaluated the effect of different LED wavelengths and photoperiods on protein productivities and free amino acid (FAA) profile of Spirulina sp. LEB 18 cultures. The best protein productivity results were obtained in red and green LED cultures using integral and partial photoperiods, respectively. In these experiments, protein productivities increased 2 and 1.6 times, respectively, compared to the control culture using fluorescent light. Green LEDs in partial photoperiod provided also the highest concentrations of essential and non-essential FAA, about 1.8 and 2.3 times higher, respectively, than control cultures. LEDs showed to be a promising sustainable light source for increasing protein productivity and FAA concentration in Spirulina sp. LEB 18 cultures.

Brackish Groundwater from Brazilian Backlands in Spirulina Cultures: Potential of Carbohydrate and Polyunsaturated Fatty Acid Production.

The composition of brackish groundwater from Brazilian backlands contains important elements necessary for metabolism in microalgae. This study evaluated the use of 100% brackish groundwater with different amounts of Zarrouk nutrients for Spirulina sp. LEB 18 cultivation. The growth parameters and biomass composition, including the concentrations of proteins, carbohydrates, ash, lipids, and fatty acids, were evaluated. The best growth parameter results were obtained in the assay using 100% brackish groundwater and only 25% of Zarrouk nutrients, which were equal to those obtained for the control culture. The concentrations of carbohydrates and polyunsaturated fatty acids were increased by as much as 4- and 3.3-fold, respectively, when brackish groundwater was used in the cultures. The lipid profile demonstrated that the biomass had the potential for use in biodiesel production. The use of brackish groundwater is a sustainable, economical way to obtain high-quality biomass for different applications during Spirulina sp. LEB 18 cultivation.

Biological CO2 mitigation by microalgae: technological trends, future prospects and challenges.

The increase in the CO2 concentration in the Earth's atmosphere has been a topic of worldwide concern since anthropogenic emissions of greenhouse gases began increasing considerably during the industrial period. The effects of these mass emissions are probably the main cause of global warming, which has been observed over recent decades. Among the various techniques of CO2 capture, microalgal biofixation by photosynthesis is considered a promising technology due to the efficiency of these microorganisms in converting this gas into organic compounds through its use as a nutrient in the culture medium. Over the years, several research centers have developed studies on this subject, which have focused on mainly the development of bioreactors, the growth conditions that increase the efficiency of the process and the production of biomass with applicability in several areas. The biological mitigation of CO2 by microalgae has many advantages, including reductions in the concentration of an industrially sourced greenhouse gas and the energy or food obtained from the produced photosynthetic biomass. This versatility allows for the cultivation of economically useful biomass while reducing the environmental impacts of industrial facilities. In this context, this mini-review aims to discuss new technologies and strategies along with the main challenges and future prospects in the field and the ecological and economic impacts of CO2 biofixation by microalgae.

Light emitting diodes applied in Synechococcus nidulans cultures: Effect on growth, pigments production and lipid profiles.

Researches about light emitting diodes (LEDs) as energy source in microalgae cultivations has been growing in recent years due to its spectral quality, durability and reduced energy consumption. In this study, green, red and yellow LEDs were evaluated as energy source in Synechococcus nidulans LEB 115 cultures. Productivities and specific growth rates were up to 2.5 times greater than in cultures using fluorescent light. The different LED colors evaluated did not influence the chlorophyll, carotenoid or lipid productions. Biomass cultivated with LEDs showed high amounts of saturated fatty acids (above 48%), which is desirable for biodiesel production. In addition to the Synechococcus nidulans LEB 115 growth stimulation, the application of green, red and yellow LEDs in the cultivations produces potential biomass for biodiesel synthesis and other industrial interest biomolecules utilization.

Spirulina cultivated under different light emitting diodes: Enhanced cell growth and phycocyanin production.

This study evaluated light emitting diodes (LEDs) as a light source in Spirulina sp. LEB 18 cultures in terms of growth parameters and biomass composition. Different photoperiods (partial and integral) and colors (blue, green, red and white) were assessed. Blue, green, red and white LEDs increased biomass productivity and maximum specific growth rate of such cultivations. The maximum biomass concentration (1.77 ±â€¯0.02 g L-1) was obtained when red LEDs in integral light photoperiod were applied to cultivations. The biomass composition showed around 12.8% carbohydrates (w w-1), 57.4% proteins (w w-1) and 12.7% lipids (w w-1). The major fatty acids produced during cultivations were palmitic, linoleic and γ-linolenic. Green LEDs in partial light photoperiod promoted a higher concentration of phycocyanin (126.39 mg gbiomass-1). The potential of LEDs as an energy source in Spirulina sp. LEB 18 cultures was demonstrated by the biomass and bioproducts photostimulation.

Blue light emitting diodes (LEDs) as an energy source in Chlorella fusca and Synechococcus nidulans cultures.

LEDs have narrow wavelength bands, which can influence microalgae biomass. This study pioneers the evaluation of blue LEDs as an energy source in Chlorella fusca and Synechococcus nidulans cultures. Blue LEDs increased the specific growth rate in Synechococcus nidulans LEB 115 cultures by 80% compared to the standard light used in indoor cultivations. Moreover, blue LEDs also induced lipid accumulation in Chlorella fusca LEB 111 cells, yielding concentrations of this bioproduct of up to 23% (ww-1). The chlorophylls and carotenoids were photostimulated proportionally to the LED light intensity. When the intensity of the blue LEDs was increased from 50 to 150µmolm-2s-1, the biomass accumulated up to 4.5 and 2.4 times more chlorophylls and carotenoids, respectively. The potential of blue LEDs as an alternative environmentally friendly light source to stimulate biomass and metabolite production for different purposes was demonstrated.

Synechococcus nidulans from a thermoelectric coal power plant as a potential CO2 mitigation in culture medium containing flue gas wastes.

This study evaluated the intermittent addition of coal flue gas wastes (CO2, SO2, NO and ash) into a Synechococcus nidulans LEB 115 cultivation in terms of growth parameters, CO2 biofixation and biomass characterization. The microalga from a coal thermoelectric plant showed tolerance up to 200ppm SO2 and NO, with a maximum specific growth rate of 0.18±0.03d-1. The addition of thermal coal ash to the cultivation increased the Synechococcus nidulans LEB 115 maximum cell growth by approximately 1.3 times. The best CO2 biofixation efficiency was obtained with 10% CO2, 60ppm SO2, 100ppm NO and 40ppm ash (55.0±3.1%). The biomass compositions in the assays were similar, with approximately 9.8% carbohydrates, 13.5% lipids and 62.7% proteins.

Biological CO2 mitigation from coal power plant by Chlorella fusca and Spirulina sp.

CO2 biofixation by microalgae and cyanobacteria is an environmentally sustainable way to mitigate coal burn gas emissions. In this work the microalga Chlorella fusca LEB 111 and the cyanobacteria Spirulina sp. LEB 18 were cultivated using CO2 from coal flue gas as a carbon source. The intermittent flue gas injection in the cultures enable the cells growth and CO2 biofixation by these microorganisms. The Chlorella fusca isolated from a coal power plant could fix 2.6 times more CO2 than Spirulina sp. The maximum daily CO2 from coal flue gas biofixation was obtained with Chlorella fusca (360.12±0.27mgL-1d-1), showing a specific growth rate of 0.17±<0.01d-1. The results demonstrated the Chlorella fusca LEB 111 and Spirulina sp. LEB 18 potential to fix CO2 from coal flue gas, and sequential biomass production with different biotechnological destinations.

Utilization of simulated flue gas containing CO2, SO2, NO and ash for Chlorella fusca cultivation.

Microalgae can use the CO2 from coal power plants in their metabolic pathways. However, these microorganisms must be able to tolerate other residues produced from burning coal. This study evaluated the wastes addition (CO2, SO2, NO and ash) present in the flue gas from a coal power plant on the growth parameters during culture, CO2 biofixation and on the biomass characterization of Chlorella fusca LEB 111. The SO2 and NO injection (until 400ppm) in cultivations did not markedly affect CO2 biofixation by microalga. The best CO2 biofixation efficiency was obtained with 10% CO2, 200ppm SO2 and NO and 40ppm ash (50.0±0.8%, w w(-1)), showing a specific growth rate of 0.18±0.01 d(-1). The C. fusca LEB 111 biomass composition was similar in all experiments with around 19.7% (w w(-1)) carbohydrates, 15.5% (w w(-1)) lipids and 50.2% (w w(-1)) proteins.