Two-step strategy for obtaining dunaliella sp. biomass and β-carotene from anaerobically digested poultry litter wastewater

Abstract

Using anaerobically digested wastewater to culture microalgae can realize wastewater treatment and biomass acquisition simultaneously. However, previous works concentrated mostly on wastewater treatment or bioenergy production, whereas few studies carried out high value-added product production. Therefore, this study focused on using anaerobically digested poultry litter wastewater (PLW) for obtaining biomass and β-carotene. The feasibility and optimal conditions for pollutant removal, biomass production, and β-carotene accumulation were investigated. The results showed that Dunaliella FACHB-558 could utilize ammonium as the sole nitrogen source. With the optimal conditions of 36 psμ salinity and 200 μmol/m2/s light intensity, the total nitrogen, total phosphorus, and total organic carbon removal, and biomass and β-carotene yields reached 63.8%, 87.2%, 64.1%, 678 mg/L, and 4.02 mg/L, respectively, after 15 days of treatment. To further improve β-carotene accumulation, a two-step strategy was adopted. By changing the culture medium from the anaerobically digested PLW to modified BG-11 medium and applying optimal culture conditions of 180 psμ salinity, 14 mg/L nitrogen, and 250 μmol/m2/s light intensity in the second step, the β-carotene yield reached 7.26 mg/L, 42.4% more than in the first step. Moreover, the salinity was found to be the most crucial factor influencing β-carotene accumulation in the second step.