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.

氨氧化古菌 (AOA) 是氮循环的主要参与者，但由于它们的生长速度缓慢且形成生物膜的趋势有限，因此它们的培养是一项重大挑战。在这项研究中，AOA 嵌入小（~2.5 毫米）和大（~4.7 毫米）聚乙烯醇（PVA）-海藻酸钠（SA）水凝胶珠中，该珠与四种试剂（钙、钡、光、或硫酸盐）以比较活性差异、氮物质（NH ₄ ⁺、NO ₂ ^-和 NO ₃ ^{- ）}的扩散率)，以及批量系统中聚合物随时间的泄漏。硫酸盐结合的 PVA-SA 珠粒是最稳定的，在不收缩的情况下释放的聚合物量最少。扩散系数被认为是高2至3倍于水凝胶比在颗粒剂，与铵扩散率是CA。比亚硝酸盐和硝酸盐多 35%。尽管小珠子的滞后期较长，但嵌入的 AOA 维持了较高的单位体积氨氧化速率，与研究和废水处理中的应用兼容。