Purple bacteria screening for photoautohydrogenotrophic food production: Are new H2-fed isolates faster and nutritionally better than photoheterotrophically obtained reference species?

Janne Spanoghe; Katharina J Ost; Wannes Van Beeck; Pieter Vermeir; Sarah Lebeer; Siegfried E Vlaeminck

doi:10.1016/j.nbt.2022.08.005

Purple bacteria screening for photoautohydrogenotrophic food production: Are new H₂-fed isolates faster and nutritionally better than photoheterotrophically obtained reference species?

N Biotechnol. 2022 Dec 25:72:38-47. doi: 10.1016/j.nbt.2022.08.005. Epub 2022 Aug 29.

Authors

Janne Spanoghe¹, Katharina J Ost¹, Wannes Van Beeck², Pieter Vermeir³, Sarah Lebeer², Siegfried E Vlaeminck⁴

Affiliations

¹ Research Group of Sustainable Energy, Air and Water Technology (DuEL), Department of Bioscience Engineering, University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp, Belgium.
² Research group of Environmental Ecology and Applied Microbiology (ENdEMIC), Department of Bioscience Engineering, University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp, Belgium.
³ Laboratory for Chemical Analysis, Department of Green Chemistry and Technology, Ghent University, Valentin Vaerwyckweg 1, 9000 Gent, Belgium.
⁴ Research Group of Sustainable Energy, Air and Water Technology (DuEL), Department of Bioscience Engineering, University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp, Belgium. Electronic address: siegfried.vlaeminck@uantwerpen.be.

PMID: 36049649
DOI: 10.1016/j.nbt.2022.08.005

Abstract

Photoautohydrogenotrophic enrichments of wastewater treatment microbiomes were performed to obtain hypothetically high-potential specialist species for biotechnological applications. From these enrichment cultures, ten photoautohydrogenotrophic species were isolated: six Rhodopseudomonas species, three Rubrivivax members and Rhodobacter blasticus. The performance of these isolates was compared to three commonly studied, and originally photoheterotrophically enriched species (Rhodopseudomonas palustris, Rhodobacter capsulatus and Rhodobacter sphaeroides), designated as reference species. Repeated subcultivations were applied to improve the initial poor performance of the isolates (acclimation effect), which resulted in increases in both maximum growth rate and protein productivity. However, the maximum growth rate of the reference species remained 3-7 times higher compared to the isolates (0.42-0.84 d^-1 at 28 °C), while protein productivities remained 1.5-1.7 times higher. This indicated that H₂-based enrichment did not result in photoautohydrogenotrophic specialists, suggesting that the reference species are more suitable for intensified biomass and protein production. On the other hand, the isolates were able to provide equally high protein quality profiles as the references species, providing full dietary essential amino acid matches for human food. Lastly, the effect of metabolic carbon/electron switching (back and forth between auto- to heterotrophic conditions) initially boosted µ_max when returning to photoautohydrogenotrophic conditions. However, the switch negatively impacted lag phase, protein productivities and pigment contents. In the case of protein productivity, the acquired acclimation was partially lost with decreases of up to 44 % and 40 % respectively for isolates and reference species. Finally, the three reference species, and specifically Rh. capsulatus, remained the most suitable candidate(s) for further biotechnological development.

Keywords: CO(2) economy; Essential amino acids; Hydrogen economy; Phototrophic purple bacteria; Purple non-sulphur bacteria; Single-cell protein.

MeSH terms

Biomass
Carbon / metabolism
Humans
Proteobacteria*
Rhodobacter sphaeroides* / metabolism

Substances

Carbon