Autotrophic, Heterotrophic, and Mixotrophic Nitrogen Assimilation for Single-Cell Protein Production by Two Hydrogen-Oxidizing Bacterial Strains

Abstract

To recover a nitrogen resource from high-ammonia-nitrogen wastewater, two amphitrophic hydrogen-oxidizing bacteria (HOB), Paracoccus denitrificans Y5 and P. versutus D6, capable of nitrogen assimilation for single-cell protein (SCP) production were isolated. These two HOB strains could grow autotrophically with H as an electron donor, O as an electron acceptor, CO as a carbon source, and ammonia nitrogen (NH-N) as a nitrogen source. The cell molecular formulas of strains Y5 and D6 determined by autotrophic cultivation were CHON and CHON, respectively. The isolated strains could synchronously remove NH-N and organic carbon and produce SCP via heterotrophic cultivation. The rates of removal of NH-N and soluble chemical oxygen demand reached 35.47 and 49.04%, respectively, for Y5 under mixotrophic cultivation conditions with biogas slurry as a substrate. SCP content of strains Y5 and D6 was 67.34-73.73% based on cell dry weight. Compared with soybean meal, the SCP of Y5 contained a variety of amino acids.

From Biogas and Hydrogen to Microbial Protein Through Co-Cultivation of Methane and Hydrogen Oxidizing Bacteria

“…could trigger methane biocatalysis with extracellular metabolites formed, such as formate, acetate, succinate, lactate, 3hydroxybutyrate and even H 2 (Kalyuzhnaya et al, 2013), that can be easily consumed by the HOB. The heterotrophic volumetric productivity of HOB is higher than that of autotrophic production (Dou et al, 2019), which can be attributed to gas-liquid mass transfer limitations. Therefore, the addition of HOB to MOB cultures has a benefit that, apart from eliminating the soluble metabolites of methanotrophic bacteria (which can further cause inhibition), it increases biomass concentration and productivity.…”

“…The general advantages of using HOB for MP production were summarized from Dou et al (2019): 1) compared to other MP types, HOB have higher protein content (i.e., 40-60% for microalgae, 30-45% for fungi and 45-55% for yeasts) (Nasseri et al, 2011); 2) they are metabolically versatile, and can switch from autotrophic to heterotrophic mode; 3) even though they are autotrophic, they do not get limited by light availability; 4) they contain intracellular products with prebiotic functions (i.e., polyhydroxybutyrate (PHB)); and 5) they fix CO 2 to protein. Similar advantages can be reported for MOB.…”

“…To our knowledge, only a few HOB strains, belonging mainly to the genera Cupriavidus (previously known as Hydrogenomonas or Alcaligenes), Azohydromonas, Herbaspirillum, Pseudomonas, Paracoccus, Sulfuricurvum, Azonexus, and Xanthobacter have been evaluated for MP production (Foster et al, 1969;Kunasundari et al, 2013;Matassa et al, 2016;Dou et al, 2019;Hu et al, 2020;Alvarado et al, 2021). At the same time, knowledge about autotrophic HOB that can be used to produce MP remains limited, while information on the use of MOB for MP production is restricted to Methylococcus capsulatus (Bath).…”

Hydrogen oxidising bacteria for production of single‐cell protein and other food and feed ingredients

“…Once a lab is established to feed mixtures of H 2 and O 2 to bacteria, HOB are fairly easy to isolate. They have been detected in many different environments, such as Antarctic subglacial lakes, temperate soils, and hot hydrothermal vents [13][14][15][16][17][18].…”

The production of single cell protein from biogas slurry with high ammonia-nitrogen content by screened Nectaromyces rattus

“…Before, the team used hydrogen oxidation bacteria to produce SCP ( Dou et al., 2019 ). The results showed that Paracoccus denitrificans Y5 could grow autotrophically with H 2 as an electron donor, CO 2 as a carbon source, and ammonia-nitrogen (NH 4 + -N) as a nitrogen source to produce SCP.…”