High-efficient nitrate conversion to protein and chlorophylls from synthetic wastewater by mixotrophic Chlorella pyrenoidosa

To achieve high-efficient conversion of nitrate to protein and chlorophylls from synthetic high-nitrate wastewater by mixotrophic Chlorella pyrenoidosa, the synergetic effects of initial NaNO3 concentration and pH-set were investigated in 5 L photo-fermenter. Results showed that the highest NO3− consumption rate (5.15 g L−1 d−1) and biomass concentration (23.40 g L−1) were achieved under 10 g L−1 NaNO3 and pH 6.5 at 60 h, along with high contents of protein (51.47 % DW) and chlorophylls (4.52 % DW). This study demonstrated the synergetic strategy was superior to enhance biomass and protein production with improvement of nitrate removal by mixotrophic fermentation of C. pyrenoidosa as cell factory, showing a great potential application in high-nitrate wastewater bioremediation and resource utilization through high-efficient conversion of NO3− to high-protein and high-chlorophyll biomass. [Display omitted] •Synergetic effects of pH and nitrate concentration improved NO3− removal by mixotrophic C. pyrenoidosa.•Maintaining a stable nitrate level was pivotal in enhancing NO3− consumption.•pH-steady at 6.5 was optimal for cell growth and protein production by photo-fermentation.•The highest NO3− consumption rate (5.15 g L−1 d−1) was achieved in 5-L photo-fermenter.