Algae, photo by Chris Weichert
In response to a growing fear surrounding increasing levels of CO2 in the atmosphere and rapidly dwindling supplies of traditional oil as a source of energy, A. Fulke et al. investigated the CO2 sequestration rate (as a source of CO2 mitigation), the biomass creation (as a source of biofuel), and lipid composition of algae used in the wastewater stabilization ponds of industrial wastewater treatment plants. The green algae species of the algae they found naturally occurring in the wastewater stabilization ponds have a lipid structure equivalent to vegetable oil currently used to produce biodiesel. In the two most dominant algal classes Chlorophyceae and Cyanophyceae, they found four distinct species (Scenedesmus dimorphus, Scenedesmus incrassatulus, Chroococcus sp. and Chlorella sp.) currently being globally explored as sources of biodiesel. They isolated and cultured samples of these four species and examined the biomass concentration, lipid content, and CO2 fixation rates, finding that the samples where all four of these species were present (as opposed to each species cultured alone) had a biomass concentration (g L-1) and lipid content (g g-1) nearly twice as high as any alone, and a CO2 fixation rate (g L-1d-1) at least double individual species cultivations. They concluded that industrial wastewater could support a diverse culture of algal species capable of being used as a source of biodiesel. —Allison Kerley
Fulke, A., Chambhare, K., Sangolkar, L., Giripunje, M., Krishnamurthi, K., Juwarkar, A., Chakrabarti, T., 2013. Potential of wastewater grown algae for biodiesel production and CO2 sequestration. African Journal of Biotechnology 12, 2939–2948.
Fulke et al. collected samples of water from ten different locations in the wastewater stabilization pond at a currently active vehicle manufacturing plant in the western Maharashtra region in India. They found 27 species of Chlorophyceae, 16 species of Cyanophycea, 14 species of Bacillariophyceae, 4 species of Euglenophyceae and 4 species of Chrysophyceae in the wastewater, with a Shannon-Wiener Diversity Index range from 2.91 to 3.66. They used the Nile Red staining method to determine the lipid content and to identify the intracellular lipid content (used in the creation of biodiesel). Four of the algae species found (Scenedesmus dimorphus, Scenedesmus incrassatulus, Chroococcus sp. and Chlorella sp). are currently being globally explored as potential sources of biodiesel, so Fulke et al. chose to further investigate the lipid content and biomass creation during stress and no-stress scenarios. They cultivated each of the species individually in the lab over 14 days, each in a culture with abundant nutrients and in a culture with limited nutrients. They found that upon nutrient depletion, the algae produce more lipids which get trapped within the cell. Cells with a higher lipid concentration are more favorable for biodiesel creation.