<p>The world cannot continue to rely on fossil fuels to meet its energy needs because of their dwindling supply and detrimental effects on the environment, among other issues. Globally, low biomass and lipid production (LP), along with the high cost of photobioreactor procurement and maintenance, hinder the production of microalgae-based biodiesel. Therefore, this study was done to maximise the biomass and lipid production for biodiesel production through optimisation of nutrients and culture parameters (50 L), while challenges associated with photobioreactors are tackled through the design and fabrication of a bench-scale cuboidal shaking photobioreactor (BCISP). Additionally, sodium nitrate, sodium chloride and dipotassium hydrogen phosphate are the nutrient concentrations optimised to regulate nutrient balance and metabolic flux, thereby enhancing biomass and lipid productivity. Culture and nutritional parameters were systematically optimised using a one-factor-at-a-time (OFAT) strategy, and optimal conditions were identified based on the highest experimentally observed biomass and lipid production. Using filtration, solvent extraction, and gravimetric techniques, the concentration of biomass, lipid extraction, and quantification were determined. Sulphuric acid was used as a catalyst for lipid transesterification into biodiesel. Gas chromatography-mass spectroscopy, the American Society for Testing for Materials’ methods and predictive models based on fatty acid composition were used for biodiesel characterisation. Culture media (BBM), light/dark cycles (12:12), agitation speed (100&#xa0;rpm), pH (7.0), nitrogen (NaNO₃), NaNO₃ (0.25&#xa0;g/L), carbon source (glucose), sodium chloride (20&#xa0;mg/L), and dipotassium hydrogen orthophosphate (<i>Scenedesmus obliquus</i> OSC, 30&#xa0;mg/L; <i>Chlorella vulgaris</i> UIA, 45&#xa0;mg/L) were the ideal physiological conditions for LP. The biodiesel has 15.7 and 18.3% polyunsaturated fatty acids, 32.5 and 31.5% monounsaturated fatty acids, and 51.80 and 50.2% saturated fatty acids. Enhanced biomass, lipid and biodiesel yields were produced in BCISP. The produced biodiesel met acceptable international requirements for both its physical and chemical characteristics. <i>Scenedesmus obliquus</i> OSC and <i>Chlorella vulgaris</i> UIA are promising for producing biodiesel. However, <i>Scenedesmus obliquus</i> OSC had better biodiesel production efficiency with biomass, lipid content, and biodiesel yield of 9.47 ± 0.03&#xa0;g/L, 71.79 ± 0.03%, and 87.80 ± 0.63%, compared to 8.05 ± 0.09&#xa0;g/L, 65.32 ± 0.46%, and 82.71 ± 0.43% recorded in <i>Chlorella vulgaris</i>.</p> Graphical Abstract <p></p>

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Optimisation of cultivation conditions for enhanced biomass and lipid production in Scenedesmus obliquus OSC and Chlorella vulgaris UIA using a locally designed bench-scale cuboidal shaking photobioreactor

  • Abideen. A. Adekanmi,
  • Abiodun. A. Onilude,
  • Emmanuel. O. Garuba,
  • Nurudeen A. Azeez,
  • Abdulhakeem. D. Olasupo,
  • Musa A. Adegboye,
  • Taoreed A. Muraina

摘要

The world cannot continue to rely on fossil fuels to meet its energy needs because of their dwindling supply and detrimental effects on the environment, among other issues. Globally, low biomass and lipid production (LP), along with the high cost of photobioreactor procurement and maintenance, hinder the production of microalgae-based biodiesel. Therefore, this study was done to maximise the biomass and lipid production for biodiesel production through optimisation of nutrients and culture parameters (50 L), while challenges associated with photobioreactors are tackled through the design and fabrication of a bench-scale cuboidal shaking photobioreactor (BCISP). Additionally, sodium nitrate, sodium chloride and dipotassium hydrogen phosphate are the nutrient concentrations optimised to regulate nutrient balance and metabolic flux, thereby enhancing biomass and lipid productivity. Culture and nutritional parameters were systematically optimised using a one-factor-at-a-time (OFAT) strategy, and optimal conditions were identified based on the highest experimentally observed biomass and lipid production. Using filtration, solvent extraction, and gravimetric techniques, the concentration of biomass, lipid extraction, and quantification were determined. Sulphuric acid was used as a catalyst for lipid transesterification into biodiesel. Gas chromatography-mass spectroscopy, the American Society for Testing for Materials’ methods and predictive models based on fatty acid composition were used for biodiesel characterisation. Culture media (BBM), light/dark cycles (12:12), agitation speed (100 rpm), pH (7.0), nitrogen (NaNO₃), NaNO₃ (0.25 g/L), carbon source (glucose), sodium chloride (20 mg/L), and dipotassium hydrogen orthophosphate (Scenedesmus obliquus OSC, 30 mg/L; Chlorella vulgaris UIA, 45 mg/L) were the ideal physiological conditions for LP. The biodiesel has 15.7 and 18.3% polyunsaturated fatty acids, 32.5 and 31.5% monounsaturated fatty acids, and 51.80 and 50.2% saturated fatty acids. Enhanced biomass, lipid and biodiesel yields were produced in BCISP. The produced biodiesel met acceptable international requirements for both its physical and chemical characteristics. Scenedesmus obliquus OSC and Chlorella vulgaris UIA are promising for producing biodiesel. However, Scenedesmus obliquus OSC had better biodiesel production efficiency with biomass, lipid content, and biodiesel yield of 9.47 ± 0.03 g/L, 71.79 ± 0.03%, and 87.80 ± 0.63%, compared to 8.05 ± 0.09 g/L, 65.32 ± 0.46%, and 82.71 ± 0.43% recorded in Chlorella vulgaris.

Graphical Abstract