Abstract: 【Objective】Ammonia is one of the most harmful gases in animal production. In order to inhibit the production of ammonia, we planned to screen microbes with the ability of ammonia removal and investigate its functional features.【Method】Ammonium sulfate was used as the sole nitrogen source to isolate the ammonia nitrogen-degrading microbe from chicken manure. Enrichment cultivation was conducted ten times. The final enrichment culture was streaked on the isolation agar after a ten-time step dilution. The colonies with different morphological characters were isolated and purified. The strain with the highest efficiency on ammonia nitrogen-degrading is our choice. The morphology, molecular biology and physiological and biochemical identification method was used to identified the target strain. Single factor experiments were conducted to identify its optimum degradation conditions, such as temperature (20, 25, 30, 35, 40℃), pH (3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0), carbon source (starch, mannitol, Na-Citrate, glucose, sodium acetate, sodium bicarbonate), C/N (5, 10, 20, 40) and initial ammonium concentrations (100, 300, 600,  1 200 mg·L^-1). The bacterial suspension was inoculated into chicken manure with the inoculation of 10%. The ammonia emissions and nitrogen forms from chicken manure were studied.【Results】Fifteen strains with the ability of ammonium-degrading were isolated from the chicken manure. One strain named LSA, showed high efficient degradation ability. The strain was identified as Candida krusei and 99% sequence similarity with 18S rDNA of Candida krusei isolate EM12（JF274497.1）was revealed compared with homologous genes in GenBank. The GenBank accession number of the strain LSA was KT025851. Further degradation studies showed that the optimal conditions for the ammonium degrading of the strain LSA were pH 3.0–7.0, 20–40°C, C/N 20 with glucose as carbon source. The removal ef?ciency increased with increasing initial NH₄⁺-N concentrations. When the initial NH₄⁺-N concentration was 327.20 mg·L^-1, the NH₄⁺-N removal rate was 71.88% and the OD₆₀₀ was 2.45 within 60h. When the initial NH₄⁺-N concentration was 1 105.26 mg·L^-1, the NH₄⁺-N removal rate was 57.44% and the OD₆₀₀ was 2.96 within 96h. The ammonium concentration and ammonia emissions from chicken manure with LSA were lower than that in the control group. The reduction rates in the treatment groups were 22.30% and 15.92%. The total nitrogen in chicken manure inoculated with strain LSA is higher than that in the control group, while the ammonia nitrogen/ total nitrogen is lower. 【Conclusion】Strain LSA has good performance in ammonium degrading and displays good potential for future applications of ammonia emission control from chicken manure.

Key words: isolation and identification, Candida krusei, ammonium, chicken manure