14 / 2021-06-22 15:04:09

Isolation and identification of thermophilic heterotrophic ammonia-oxidizing bacteria from chicken manure composting

Composting; Thermophilic; Heterotrophic ammonia-oxidizing bacteria; Aneurinibacillus thermoaerophilus; Bacillus coagulans

Composting is a general treatment for recycling animal wastes as plant fertilizer. During the treatment, however, large amounts of malodorous gases are emitted, ammonia (NH₃) is largely emitted when organic matter is actively decomposed and the material temperature rises to above 60 ℃, which is considered to be the element most responsible for malodor from composting. This causes a decline in the value of the compost as a fertilizer, as well as complaints about malodor. Additionally, NH₃ emission from animal wastes is one of the main causes of wider environmental pollution so reducing the emission has come to be a significant problem.

This research aimed to screen the thermophilic heterotrophic ammonia-oxidizing bacteria which will be used in compost to identify their ammonia-oxidizing characteristics. Dilute spread plate method and Griess reagent coloration method were used to screen thermophilic heterotrophic ammonia-oxidizing bacteria, and medium with NH⁴⁺ used to identify the optimum growth temperature and pH value, rates of ammonia-oxidizing, nitrite- and nitrate-producing of the ammonia oxidizing bacteria. 16S rDNA sequencing, blast-comparison and phylogenetic analysis were used to compare the ammoniaoxidizing bacteria. Two heterotrophic thermophilic ammonia-oxidizing bacterial strains, D3A and D26, were isolated from chicken composting. Their nearly full-length16S rDNA sequence analysis showed that they are mostly similar to  Aneurinibacillus thermoaerophilus strain DSM 10154 and  Bacillus coagulans NBRC 12583. Genus Aneurinibacillus are closely related in classification  with genus Ammoniphilus, and  Aneurinibacillus group belonging to family Paenibacillaceae contains three genera: Ammoniphilus, Aneurinibacillus, and Oxalophagus. The strain D26 belonging to Bacillus coagulans grows weakly in LB medium and grows well in Lactobacillus MRS medium. The results demonstrated that strains D3A and D26 are heterotrophic ammonia-oxidizing bacteria which can oxidize NH⁴⁺ into NO^2- and NO^3-, with NO^3- as the main product. These bacteria are expected to be applied in reducing ammonia emissions and increasing nitrogen content in compost.