Abstract
In this research, the physiological response of the microalgae Spirulina platensis to salinity stress (1 and 100 g L-1 ) was investigated. Spirulina platensis and Spirulina platensis (adapted to high salt concentration) were operated at laboratory scale in a semi-continuous photobioreactors. The responses examined were within 0.5 to 10% CO2 concentration, temperatures from 10 to 40 oC, light intensities from 60 to 200 μmol m-2 s -1 and presented better results in terms of all kinetic parameters. The highest rate of CO2 biofixation for Spirulina platensis was 25.1 gCO2 m-3 h -1 , and the maximum specific growth (μmax) achieved was 0.44 d-1 - 0.67 d-1 at 2.5% CO2, 150 µmol m-2 s -1 at 25 oC. Corresponding determined values of Spirulina platensis adapted were 18.2 gCO2 m-3 h -1 , 0.31 d-1 - 0.58 d-1 at 2.5% CO2, 60 µmol s-1 m-2 and 28 oC. However, both microalgae exhibited experimental limiting growth factors, CO2 10%, 40 oC and 200 µmol m-2 s -1 , conditions under which photosynthetic CO2 biofixation may be inhibited and photoinhibition of photosynthesis may be enhanced by salinity. The efficiency of 2.5% CO2 removal by Spirulina platensis achieved 99%, whereas Spirulina platensis adapted to 96%, respectively. The kinetic parameters estimated for Spirulina platensis can be used to improve photobioreactor design for reducing of atmospheric carbon dioxide.
Highlights
Global warming is generally attributed to greenhouse gases (GHG) increase in the atmosphere, carbon dioxide (CO2), for which atmospheric concentration has already achieved 387 ppm and needs to get down to 350 ppm or less in order to avoid global climate change consequences[1,2]
The experimental results were evaluated by comparing the specific growth rates of CO2input is the initial and (CO2) biofixation by S. platensis and S. platensis adapted to salinity under different environmental conditions in photobioreactors and analysis of variance (ANOVA) of the kinetic parameters, significance was tested by Tukey at p < 0.05, using R software[16]
The results demonstrated that S. platensis adapted to high salinity media 1.71 mol L-1 cultivated at 200 μmol s-1 m-2, 40 °C and high CO2 concentrations (7.5 and 10%) inhibit microalgae grow, show low photosynthetic activity and photoinhibition[20]
Summary
Global warming is generally attributed to greenhouse gases (GHG) increase in the atmosphere, carbon dioxide (CO2), for which atmospheric concentration has already achieved 387 ppm and needs to get down to 350 ppm or less in order to avoid global climate change consequences[1,2]. By 2100, 26 billion tons of CO2 are estimated to be released into the atmosphere from anthropogenic sources[3] Photosynthetic organisms such as microalgae species are potent producers of value-added bioactive compounds such as pigments, vitamins and long-chain polyunsaturated fatty acids, when grown under stress conditions can accumulate significant quantities of total lipids[4,5,6]. S. platensis incorporates into a suitable photo-bioreactor configuration that can enhance photosynthesis by increasing growth conditions and controlling exposure of S. platensis to environmental factors, as well as suitable for greenhouse gases attenuation, converting CO2 into biomass in which carbon is biofixed and incorporated into carbohydrates, lipids and proteins[10,11]. In this paper, were studied the impacts of light intensity, temperature, and inlet CO2 concentration on the specific growth rate of S. platensis and S. platensis adapted to salinity-stress during biofixation of CO2 in photobioreactors at laboratory scale
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