Operational Strategies to Selectively Produce Purple Bacteria for Microbial Protein in Raceway Reactors

Abbas Alloul, Marta Cerruti, Damian Adamczyk, David G. Weissbrodt, Siegfried E. Vlaeminck*

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

16 Citations (Scopus)
4 Downloads (Pure)


Purple non-sulfur bacteria (PNSB) show potential for microbial protein production on wastewater as animal feed. They offer good selectivity (i.e., low microbial diversity and high abundance of one species) when grown anaerobically in the light. However, the cost of closed anaerobic photobioreactors is prohibitive for protein production. Although open raceway reactors are cheaper, their feasibility to selectively grow PNSB is thus far unexplored. This study developed operational strategies to boost PNSB abundance in the biomass of a raceway reactor fed with volatile fatty acids. For a flask reactor run at a 2 day sludge retention time (SRT), matching the chemical oxygen demand (COD) loading rate to the removal rate in the light period prevented substrate availability during the dark period and increased the PNSB abundance from 50-67 to 88-94%. A raceway reactor run at a 2 day SRT showed an increased PNSB abundance from 14 to 56% when oxygen supply was reduced (no stirring at night). The best performance was achieved at the highest surface-to-volume ratio (10 m2 m-3 increased light availability) showing productivities up to 0.2 g protein L-1 day-1 and a PNSB abundance of 78%. This study pioneered in PNSB-based microbial protein production in raceway reactors, yielding high selectivity while avoiding the combined availability of oxygen, COD, and darkness.

Original languageEnglish
Pages (from-to)8278-8286
JournalEnvironmental Science and Technology
Issue number12
Publication statusPublished - 2021

Bibliographical note

Accepted Author Manuscript


  • alternative protein source
  • anaerobic fermentation
  • carboxylate platform
  • high-rate algae pond
  • nutrient recovery
  • purple phototrophic bacteria
  • short-chain fatty acid
  • single-cell protein


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