N2‐fixation can sustain wastewater treatment performance of photogranules under nitrogen‐limiting conditions. Issue 5 (25th February 2023)

• Record Type: Journal Article
• Authors: Trebuch, Lukas M.; Schoofs, Kobe; Vaessen, Stijn M. F.; Neu, Thomas R.; Janssen, Marcel; Wijffels, René H.; Vet, Louise E. M.; Fernandes, Tânia V.
• Is Part Of: Biotechnology and bioengineering. Volume 120:Issue 5(2023)
• Page Start: 1303
• Page End: 1315
• Publication Date: 2023-02-25
• Subjects: confocal laser scanning microscopy -- FAPROTAX -- functional annotation -- microalgal‐bacterial granules -- nitrogen fixation -- nitrogen limitation; Biotechnology -- Periodicals; Bioengineering -- Periodicals; 660.6
• DOI: 10.1002/bit.28349
• Languages: English
• ISSNs: 0006-3592

Abstract

Abstract: Wastewater characteristics can vary significantly, and in some municipal wastewaters the N:P ratio is as low as 5 resulting in nitrogen‐limiting conditions. In this study, the microbial community, function, and morphology of photogranules under nitrogen‐replete (N+) and limiting (N−) conditions was assessed in sequencing batch reactors. Photogranules under N− condition were nitrogen deprived 2/3 of a batch cycle duration. Surprisingly, this nitrogen limitation had no adverse effect on biomass productivity. Moreover, phosphorus and chemical oxygen demand removal were similar to their removal under N+ conditions. Although performance was similar, the difference in granule morphology was obvious. While N+ photogranules were dense and structurally confined, N− photogranules showed loose structures with occasional voids. Microbial community analysis revealed high abundance of cyanobacteria capable of N2 ‐fixation. These were higher at N− (38%) than N+ (29%) treatments, showing that photogranules could adjust and maintain treatment performance and high biomass productivity by means of N2 ‐fixation. Abstract : In this study, photogranules were cultivated under nitrogen‐replete and nitrogen‐limiting conditions. Despite nitrogen limitation, photogranules maintained wastewater treatment performance by means of N2 ‐fixation. N2 ‐fixation was mainly attributed to filamentous cyanobacteria that are highly abundant in the microbial community and play an important role in photogranule formation.