Ammonia inhibition in oleaginous microalgae

Waste-streams containing nitrogen (commonly as NH3/NH4+) have been promoted as a means to lower the energy burden and improve the overall sustainability of microalgae-based fuel and chemical production. However, beyond a concentration threshold, ammonia (NH3) is toxic to many microalgae. This study investigated the ammonia tolerances of oleaginous microalgae. Four microalgae that are often considered in biofuel production studies (Neochloris oleoabundans, Dunaliella tertiolecta, Chlorella sorokiniana and Nannochloropsis oculata) were grown in batch reactors maintained at 10 different NH4Cl concentrations at a constant pH = 8. Growth rates and lipid profiles were monitored. Ammonia acted as an inhibiting substrate for N. oleoabundans and D. tertiolecta at 2.3 and 3.3 mg L-1 NH3, respectively. Growth rates for C. sorokiniana and N. oculata were largely unaffected by ammonia concentrations. D. tertiolecta demonstrated significant neutral lipid alterations during ammonia inhibition. (C) 2016 Elsevier B.V. All rights reserved.