(592b) Lipid Accumulation in Municipal Sewage Activated Sludge Microflora Via Fermentation of Lignocellulose Hydrolyzate

A biorefinery concept utilizing an existing municipal wastewater treatment plant infrastructure, wastewater influent, and waste activated sludge will be presented. Sugars derived from the hydrolysis of lignocellulose biomass can be utilized by activated sludge microflora as substrates in a fermentation process to produce lipids for biofuel applications. Batch fermentation experiments were conducted using a 20 % (v/v) inoculum of waste activated sludge in a synthetic wastewater medium. An artificial lignocellulose hydrolyzate containing glucose, xylose, furfural, and/or acetic acid was used as the substrate. Experiments were conducted using glucose or xylose as the sole carbon source at a constant initial C:N mass ratio of 78.6. Three initial furfural (0.5, 1.5, 2.5 g/L), and three initial acetic acid levels (2, 6, 10 g/L) were tested to determine the inhibitory effects of these lignocellulose hydrolysis by-products on the growth, lipid accumulation, and substrate utilization of activated sludge microflora. The cell biomass were harvested and tested for lipid yields using the Bligh and Dyer extraction method while culture broth samples were analyzed for residual sugar and N-NH4+. The lipid extracts were analyzed for fatty acid composition by gas chromatography. Mathematical models of cell growth, lipid accumulation and sugar utilization, which can be applied to design a wastewater treatment facility capable of generating lipid feedstocks for the production of biofuels, were developed. The calculated kinetic parameters and biomass and lipid yields were compared between glucose and xylose as the sole carbon source; and at different levels of furfural and acetic acid in the media. Economic analysis of the proposed biorefinery concept was conducted to determine the feasibility of conducting the process in a commercial scale.