Thermophilic Heterotrophic Ammonia-Oxidizing Bacteria And Their Effect On Composting Process

Nitrogen (N) is a necessary nutrient for all organisms. Ammonia oxidation is performed by ammonia-oxidizing bacteria, which is the central part in the global nitrogen cycle. Thermophilic bacteria were bacteria or archaea being able to survive at high temperature, and widely distributed in natural or artificial hot zones. Composting process is a common method of treating organic waste which is a simple operation. However, ammonia volatilization during composting could cause air pollution. Thermophilic heterotrophic ammonia-oxidizing bacteria could quickly and effectively reduce the ammonia emissions in the high temperature composting core.Four heterotrophic ammonia oxidizing bacterial strains named TG4, NC8, NJ26and gxl were isolated from Dali Eryuan hot spring zone by using dilute spread plate and Griess reagent colorimetric method, and medium with NH4+was used to identify the optimum pH value and growth temperature, rates of ammonia-oxidizing, nitrite-and nitrate-producing of the ammonia-oxidizing bacteria. And the ammonia-oxidizing bacteria were identified by16S rRNA gene sequencing, Blast-comparison and phylogenetic analysis. Results showed that the optimum growth temperature and growth pH were55℃and8.0, respectively. Under optimum growth condition, the average NH4+unit volume reduction rates of these strains, TG4, NC8. NJ26and gx1, were100.3mg/(L·d),103.3mg/(L·d),118.4mg/(L·d), and167.5mg/(Ld), respectively; the average NO2-unit volume production rates of these strains were22.86mg/(L·d),2.38mg/(L·d),3.38mg/(L/d) and4.52mg/(L·d), respectively. Moreover, the average NO3-unit volume production rates of these strains were32.82mg/(L·d),27.23mg/(L·d),36.67mg/(L·d) and48.48mg/(L·d), respectively.The16S rRNA gene sequences analysis showed that strain TG4and NC8had the highest similarity with Brevibacillus thermoruber and Bacillus thermolactis, NJ26and gxl should belong to different species of genus Bacillus, and needed further identification. Amplification of amoA and hao gene has been tried. However, it was unsuccessful due to the strong species-specific of amoA and hao gene. During the14-day-composting experiments, the average NH3emission reduction rate of the mixed4cultured bacteria was16.25ppm/d, the average NH4+reduction rate was31.47mg/(g·d), moreover, the average NO2-and NO3-production rates were0.022mg/(g·d) and0.45mg/(g·d), respectively. All results demonstrated that strains TG4, NC8, NJ26and gxl are heterotrophic ammonia-oxidizing bacteria which can oxidize NH4+into NO2-and NO3-, with NO3-as the main product. Moerover, the bacterial strains could reduce NH3emissions in the compsting experiments and produce NO2-and NO3-contents. These bacteria are expected to be applied in reducing ammonia emissions and increasing nitrogen content in compost.