Abstract
Background:Microalgae remove nutrients from wastewater with the possibility of grow in mixotrophic and heterotrophic cultures. However, the effluent quality can modify the profile of fatty acids and biodiesel quality.Methods:Phototrophic and mixotrophic (light / dark; 12/12 h) cultures ofScenedesmus obliquuson domestic wastewater (WW) and Artificial Wastewater (AW) was carried out to evaluate the lipid accumulation and fatty acid methyl esters profile. The microalgae was first cultivated in an enriched medium (90 mg N-NH4 L-1) and subsequently under nitrogen limitation (30, 20 and 10 mg N L-1) using a two-stage process for both culture media.Results:A higher cell density in enriched AW medium was obtained in phototrophic and mixotrophic culture of 19 x 106cell mL-1and 20 x 106cell mL-1, respectively; than for WW (13 x 106cell mL-1and 14 x 106cell mL-1, respectively). The nitrogen limitation (from 90 to 20 mg N L-1) for AW increased the lipid content by 5.0% and 17.28% under phototrophic and mixotrophic conditions, respectively and only 5% for WW in mixotrophic culture.Conclusion:The high Cetane Number (CN) show a positive correlation with high Saturated Fatty Acids (SFA) content and negative correlation with the Degree of Saturation (DU), suggesting a good ignition of fuel. The Cold Filter Plugging Point (CFPP) (-6.02 to -8.45 °C) and Oxidative Stability (OS) (3.53 - 6.6 h) propose toScenedesmus obliquusas a candidate in the production of biodiesel and potential application for an integral urban wastewater treatment system.
Highlights
In recent years, environmental issues in relation to the effects caused by the high consumption of fossil fuels and the progressive depletion of this resource in many countries have motivated new research aimed at the1874-0707/18 2018 Bentham Open230 The Open Biotechnology Journal, 2018, Volume 12Ruiz-Marin et al.exploration of new renewable energy sources such as the use of microalgal biomass to obtain lipids and synthesis of biodiesel [1]
The values of lipid production (% w / w) were low in WW compared to those obtained in Artificial Wastewater (AW), the results suggest that the microalga had the capacity to increase the lipid content under the mixotrophic condition and nitrogen limitation in urban wastewater
The present study shows the potential of the use of a low-cost algal culture medium such as urban wastewater for the production of high-quality biomass and biodiesel compared to a conventional medium
Summary
Environmental issues (climate change) in relation to the effects caused by the high consumption of fossil fuels and the progressive depletion of this resource in many countries have motivated new research aimed at the1874-0707/18 2018 Bentham Open230 The Open Biotechnology Journal, 2018, Volume 12Ruiz-Marin et al.exploration of new renewable energy sources such as the use of microalgal biomass to obtain lipids and synthesis of biodiesel [1]. Microalgae have shown important properties such as high photosynthetic efficiency, high rates of lipid accumulation and high biomass production. Some of the microalgae species reserve high lipid content (above 70%) under conditions of environmental stressors such as limitation of essential nutrients as nitrogen, phosphate and some metals. High lipids contents produced under nutrient limitation conditions are usually associated with low algal biomass productivity. Producing sufficient biomass with enhanced lipids contents can be done using a two-stage culture strategy [4]. In this strategy, an alga is first grown under nutrientsufficient conditions to allow maximum cell density, and deprived of certain nutrients to trigger lipids accumulation [4, 5]. The effluent quality can modify the profile of fatty acids and biodiesel quality
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