Abstract
Ammonia-oxidizing archaea (AOA) are major players in the nitrogen cycle but their cultivation represents a major challenge due to their slow growth rate and limited tendency to form biofilms. In this study, AOA was embedded in small (~2.5 mm) and large (~4.7 mm) poly(vinyl alcohol) (PVA)—sodium alginate (SA) hydrogel beads cross-linked with four agents (calcium, barium, light, or sulfate) to compare the differences in activity, the diffusivity of nitrogen species (NH4+, NO2−, and NO3−), and polymer leakage in batch systems over time. Sulfate-bound PVA-SA beads were the most stable, releasing the lowest amount of polymer without shrinking. Diffusion coefficients were found to be 2 to 3 times higher in hydrogels than in granules, with ammonium diffusivity being ca. 35% greater than nitrite and nitrate. Despite a longer lag phase in small beads, embedded AOA sustained a high per volume rate of ammonia oxidation compatible with applications in research and wastewater treatment.
Highlights
Ammonium-oxidizing archaea are one of the most dominant clades of mesophilic and thermophilic Thaumarchaeota
Macroscopic observations of small (SB) and large (LB) hydrogel beads cross-linked with barium (Ba2+), calcium (Ca2+), blue light (Sbq), and either sulfate 6% (SO42− 6%) or 10% (SO42− 10%)
The impact of polymerization on the size and shape of hydrogel carriers and cell viability can greatly influence the accessibility of microorganisms to nutrients and microbial growth within the polymer matrix[38]
Summary
Ammonium-oxidizing archaea are one of the most dominant clades of mesophilic and thermophilic Thaumarchaeota. Macroscopic observations of small (SB) and large (LB) hydrogel beads cross-linked with barium (Ba2+), calcium (Ca2+), blue light (Sbq), and either sulfate 6% (SO42− 6%) or 10% (SO42− 10%).
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