Enhanced microalgal biomass and lipid production from a consortium of indigenous microalgae and bacteria present in municipal wastewater under gradually mixotrophic culture conditions

Abstract The goal of this study was to investigate the influences of gradually mixotrophic culture conditions on microalgal biomass and lipid production by a consortium of indigenous microalgae and bacteria present in raw municipal wastewater. Lab-scale photobioreactors containing the consortium were operated in repeated batch mode. Initial cultivation (phase I) was performed using only the municipal wastewater, then 10% and 25% of the reactor volumes were replaced with the effluent from a sewage sludge fermentation system producing volatile fatty acids (SSFV) at the beginnings of phase II and phase III, respectively. The highest biomass productivity (117.1 ± 2.7 mg/L/d) was attained during phase II, but the lipid productivity (17.2 ± 0.2 mg/L/d) was attained during phase III. The increase in the effluent from the SSFV influenced microalgal diversity with a preference for Chlorella sp., but bacterial diversity increased significantly during phase III.