Cultivation of methanotrophic bacteria in a novel bubble-free membrane bioreactor for microbial protein production

Borja Valverde Pérez*, Wei Xing, August Axel Zachariae, Monika M. Skadborg, Astrid F. Kjeldgaard, Alejandro Palomo, Barth F. Smets

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

Microbial protein is proposed as an alternative protein source with low environmental impact. Methane oxidizing bacteria are already produced at commercial scale from natural gas. However, their productivity is limited because of the creation of explosive atmospheres in the fermenters during production. This work demonstrates the applicability of bioreactors with a membrane-based gas supply via diffusion. Methanotrophic bacteria were successfully cultivated, with growth yields from 0.26 to 0.43 g-VSS g-CH4 −1, slightly below those observed in analogous fermenters relying on bubbling. However, ammonia yields ranged from 5.2 to 6.9 g-VSS g-NH3 −1, indicating higher nitrogen assimilation than in conventional fermenters. Indeed, protein content increased during the operational period reaching up to 51% of dry weight. The amino acid profile included the majority of the essential amino acids, demonstrating suitability as feed ingredient. Never during the operational period was an explosive atmosphere established in the reactor. Thus, bubble-free membrane bioreactors are a promising technology for microbial protein production relying on explosive gas mixtures.

Original languageEnglish
Article number123388
JournalBioresource Technology
Volume310
Number of pages8
ISSN0960-8524
DOIs
Publication statusPublished - 2020

Keywords

  • Hydrophobic membranes
  • Methane oxidizing bacteria
  • Microbial protein
  • Nutrient upcycling

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