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Fatty Acid and Lipid Accumulation In Municipal Wastewater Microorganisms Growing on a Nitrogen-Limited Synthethic Wastewater Medium

Andro Mondala, Rafael Hernandez, Todd French, Earl Alley, and Maria Paraschivescu. Chemical Engineering, Mississippi State University, Box 9595, Mississippi State, MS 39762

The potential for accumulating lipids and fatty acids in the indigenous microbial population in municipal wastewater was investigated. These lipids and fatty acids could then be used as feedstocks for the production of biofuels such as biodiesel and green diesel. A 5 % (v/v) inoculum of activated sludge from a wastewater treatment plant in Tuscaloosa, AL was grown under excess carbon and nitrogen-limited conditions in a batch culture using a synthetic wastewater medium. Glucose concentrations of 4, 8, 12, and 20 g/L in the medium were tested and samples were analyzed for cell mass (dry basis), glucose uptake, and ammonium-nitrogen concentration. The microbial cells were then harvested and the accumulated lipids and fatty acids in these cells were extracted using the method of Bligh and Dyer (1959). The extracts were then weighed to determine the gravimetric yield in terms of cell dry mass and then analyzed as their methyl esters by gas chromatography. The kinetics of oil accumulation and glucose uptake were determined and applied to design a wastewater treatment facility capable of generating oil for biofuels production.