Abstract: A nitrifying bacteria formulation that can cause a sufficient nitrification reaction even in a high ionic concentration (salt concentration), and efficiently collect high-concentration nitrate-form nitrogen from ammonia produced in animal husbandry facilities, composting facilities, sewage treatment plants, etc.; and a method for culturing bacteria to be contained in the nitrifying bacteria formulation. A nitrifying bacteria formulation includes: ammonia-oxidizing bacteria and nitrite-oxidizing bacteria, wherein the ammonia-oxidizing bacteria include bacteria belonging to the Nitrosococcus, the proportion of the number of the bacteria belonging to the Nitrosococcus with respect to the total number of bacteria in the nitrifying bacteria formulation is at least 0.1%, and the proportion of the number of the nitrite-oxidizing bacteria with respect to the total number of bacteria in the nitrifying bacteria formulation is at least 0.1%.

Abstract: This nitrogen recovery method is for causing nitrifying bacteria to decompose an ammonia component in an ammonia-containing gas, and recovering a nitrogen component contained in ammonia as an ammonia gas decomposition product, involving: supplying circulating water to a microorganism decomposition tank retaining a nitrifying bacterium carrier carrying nitrifying bacteria to maintain the carrier wet; passing ammonia-containing gas through the carrier in the wet state in an oxygen-containing atmosphere; dissolving an ammonia component in the ammonia-containing gas in the circulating water, together with an ammonia gas decomposition product produced by the nitrifying bacteria, to continue decomposing the ammonia-containing gas while the decomposition product is accumulated in the circulating water; and collecting all or a portion of the circulating water to recover the ammonia gas decomposition product, when the concentration of nitrate ion as an ammonia decomposition product in the circulating water reaches a p