The microbial community ecology of various systems for the cultivation of algal biodiesel

Abstract

Algal based biofuel has the potential to aid in offsetting future fossil fuel consumption and demand, and lowering CO 2 emissions. Cultivation strategies are a pivotal component of achieving high biomass yield. Open outdoor pond systems are currently the most economically viable method for large-scale algae cultivation due to less energy for maintenance than closed systems. However, open pond cultivation is subject to microbial colonization, sometimes negatively impacting the algal crop. Thus, large-scale production is hindered by gaps in our fundamental understanding of microbial interactions and ecology. The following research aims to explore the interplay between cultivation methods, nutrient availability, community composition, lipid metabolism, and system ecology and identify cost effective concepts for algal lipid production. Using alkalinity to limit microbial colonization of an open system is investigated in Chapter 2 in which a monoculture of Chlorella vulgaris was successfully cultivated. A putative relationship with a Pseudomonas sp. was identified in which the exchange of key metabolites could have enhanced algal growth and limited contamination. Such interactions may minimize the need for pesticides and fertilizer subsequently reducing pollution and operating costs. Findings suggested that potentially beneficial algal-bacterial relationships occurring in alkaline conditions supported a productive and stable monoculture. Alkalinity, in addition to nutrient abundance, is further explored in a natural freshwater terminal lake system, presented in Chapter 3. Lake eutrophication coupled with temperature increases led to a toxic cyanobacterial bloom that reduced overall eukaryotic diversity. Insight gained on the interplay between alkalinity, nutrients, and community dynamics from this natural system was then applied to a series of artificial wastewater lagoons Chapter 4. Elevated lipid (g/L) was observed in this system partially facilitated by increased water residence time in the lagoons and elevated nitrogen availability. Differing alga community composition were observed during periods of elevated lipid in addition to higher biomass (cells/mL) suggesting that higher lipid volumes were the result of high biomass concentration and not necessarily the lipid productivity of specific alga taxa. The research presented utilizes traditional ecologic concepts like diversity and contributes to a more comprehensive understanding of community interactions helping to minimize cost, reduce pollution, and ultimately contribute to the realization of viable biodiesel.