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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., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

To achieve a high consumption rate of ammonium with biomass coproduction, the mixotroph Chlorella pyrenoidosa was cultivated in high ammonium-high salinity wastewater medium in this study. The initial cell density, glucose and ammonium concentrations, and light intensity were optimized in shake flasks. A 5-L fermenter with surrounding LED (Light Emitting Diode) and a 50-L fermenter with inlet LED were employed for batch and semicontinuous cultivation. The results demonstrated that the highest contents of protein (56.7% DW) and total pigments (4.48% DW) with productivities of 5.62 g L -1 d -1 and 0.55 mg L -1 d -1 , respectively, were obtained in 5-L photofermenter, while the maximum NH 4 + consumption rate (1,800 mg L -1 d -1 ) and biomass yield (23.6 g L -1 ) were achieved in 50-L photofermenter. This study developed a novel strategy to convert high ammonium in wastewater to high-protein algal biomass, facilitating wastewater bioremediation and nitrogen recycling utilization by the mixotroph C. pyrenoidosa in photofermentation., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)