Mass Cultivation of Microalgae on Animal Wastewater: a Sequential Two-Stage Cultivation Process for Energy Crop and Omega-3-Rich Animal Feed Production Wenguang Zhou & Bing Hu & Yecong Li & Min Min & Michael Mohr & Zhenyi Du & Paul Chen & Roger Ruan Received: 23 April 2012 / Accepted: 13 June 2012 / Published online: 14 July 2012 # Springer Science+Business Media, LLC 2012 Abstract In this study, 97 microalgal strains purchased from algae bank and 50 microalgal strains isolated from local waters in Minnesota were screened for their adaptability growing on a 20-fold diluted digested swine manure wastewater (DSMW). A pool of candidate strains well adapted to the DSMW was established through a high-throughput screening process. Two top-performing facultative heterotrophic strains with high growth rate (0.536 day -1 for UMN 271 and 0.433 day -1 for UMN 231) and one strain with high omega-3 unsaturated fatty acid (EPA, 3.75 % of total fatty acids for UMN 231) were selected. Subsequently, a sequential two-stage mixo-photoautotrophic culture strategy was developed for biofuel and animal feed production as well as simultaneous swine wastewater treatment using above two strains. The maximal biomass concentration and lipid content at the first and second stages reached 2.03 g/L and 23.0 %, and 0.83 g/L and 19.0 % for UMN 271 and UMN 231, respectively. The maximal nutrient removals for total phosphorus and ammonia after second-stage cultivation were 100 and 89.46 %, respectively. The experi- ments showed that this sequential two-stage cultivation process has great potential for economically viable and environmentally friendly production of both renewable biofuel and high-value animal feed and at the same time for animal wastewater treatment. Keywords Animal feed . Swine manure wastewater . Energy crop . Facultative heterotrophic microalgae . Mixo-photoautotrophic cultivation . Omega-3 fatty acid Appl Biochem Biotechnol (2012) 168:348–363 DOI 10.1007/s12010-012-9779-4 W. Zhou : B. Hu : Y. Li : M. Min : M. Mohr : Z. Du : P. Chen : R. Ruan Center for Biorefining, Bioproducts and Biosystems Engineering Department, University of Minnesota, 1390 Eckles Ave, Saint Paul, MN 55108, USA R. Ruan (*) Bioproducts and Biosystems Engineering Department, University of Minnesota, 1390 Eckles Ave, Saint Paul, MN 55108, USA e-mail: ruanx001@umn.edu R. Ruan Nanchang University, MOE Center for Biomass Engineering Research, 235 East Nanjing Road, Nanchang, Jiangxi 330047, People’ s Republic of China