Mixotrophic Chlorella pyrenoidosa as cell factory for ultrahigh-efficient removal of ammonium from catalyzer wastewater with valuable algal biomass coproduction through short-time acclimation

To achieve ultrahigh-efficient ammonium removal and valuable biomass coproduction, Chlorella -mediated short-time acclimation was implemented in photo-fermentation. The results demonstrated short-time acclimation of mixotrophic Chlorella pyrenoidosa could significantly improve NH 4 + removal and biomass production in shake flasks. After acclimation through two batch cultures in 5-L photo-fermenter, the maximum NH 4 + removal rate (1,400 mg L -1 d -1 ) were achieved under high NH 4 + level (4,750 mg L -1 ) in batch 3. In 50-L photo-fermenter, through one batch acclimated culture, the maximum NH 4 + removal rate (2,212 mg L -1 d -1 ) and biomass concentration (58.4 g L -1 ) were achieved in batch 2, with the highest productivities of protein (5.56 g L -1 d -1 ) and total lipids (5.66 g L -1 d -1 ). The hypothetical pathway of nutrients assimilation in mixotrophic cells as cell factory was proposed with detailed discussion. This study provided a novel strategy for high-ammonium wastewater treatment without dilution, facilitating the algae-based “waste-to-treasure” bioconversion process for green manufacturing.