Abstract
Chlorella ellipsoidea and Chlorococcum infusionum, promising microalgae for biodiesel feedstock production, were treated with ethylenediaminetetraacetate (EDTA) and phosphorous to induce stress which was then followed by flow cytometry to study the enhanced intracellular neutral lipid content. Treatment resulted in up to a threefold increase in total lipid content of Chlorella (41.8±1.9% at 16 days of incubation period) and more than twofold increases in Chlorococcum (31.3±1.0% at 18 days of incubation period) under phosphorous starvation in the culture. It was observed that maximum biomass yields in Chlorella and Chlorococcum were 1.56±0.06 and 2.17±0.12 g/L at 1.5 g/L of phosphorous after 20 and 18 days of incubation periods, respectively. The qualitative analyses of neutral lipid bodies under stress conditions were performed by confocal microscopy and revealed bright golden-yellow lipid droplets in stress exposed cells. Significant increase of monounsaturated fatty acids under the nutrient limited conditions was suitable to produce biodiesel. The maximum biomass (g/L) and lipid content (% dry cell weight) at different stresses showed significant results (p<0.05) by single-factor Analysis of Variance (ANOVA) followed by Duncan’s Multiple Range Test (DMRT).
Highlights
Continued exploitation of the world’s fossil fuel reserves is unsustainable due to their depleted status and simultaneous steady accumulation of greenhouse gases in the atmosphere
Culture of Chlorococcum showed biomass yield of 1.45 ± 0.06 g/L after 18 days of incubation when exposed to 0.08 g/L EDTA (Figure 1(c))
It can be stated that the flow cytometry is the most modern and useful technique to screen potential microalgae suitable for biodiesel production
Summary
Continued exploitation of the world’s fossil fuel reserves is unsustainable due to their depleted status and simultaneous steady accumulation of greenhouse gases in the atmosphere. Development of sustainable energy sources is necessary to overcome this problem. The production of biodiesel from photosynthetic microorganisms is considered as an effective strategy to produce renewable energy. One of the most promising candidates for production of alternative energy is microalgae because of their higher growth rate and oil content than those of the conventional energy crops such as jatropha, soybean, palm, canola, and corn [1,2,3]. Some conditions of cultivation should be strategically changed to enhance microalgal lipid. Most recent studies have found that the lipid accumulation in microalgae could be increased through altering parameters such as temperature, light, CO2, salinity, and nutrient concentration [4,5,6,7,8,9,10]
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