Effects of microbial deodorizer on pig feces fermentation and the underlying deodorizing mechanism

Microbial deodorization is a novel strategy for reducing odor in livestock and poultry feces. Herein, 12 strains of ammonia (NH₃) and 15 hydrogen sulfide (H₂S) removing bacteria were obtained with a removal efficiency of 65.20-79.80% and 34.90-79.70%, respectively. A novel bacteria deodorant named MIX (Bacillus zhangzhouensis, Bacillus altitudinis, and Acinetobacter pittii at a ratio of 1:1:2) were obtained. MIX can shorten the temperature rising stage by 2 days and prolong the thermophilic stage by 4 days. The ability of MIX to remove NH₃, H₂S, and volatile fatty acids (VFAs) and the underlying removal mechanism were analyzed during pig feces fermentation. MIX can significantly reduce the concentrations of NH₃ and H₂S by 41.82% and 66.35% and increase the concentrations of NO₃^--N and SO₄^2- by 7.80% and 8.83% (P < 0.05), respectively, on the 25th day. Moreover, the concentrations of acetic, propionate, iso-valerate, and valerate were significantly reduced. The dominant bacteria communities at the phylum level were Firmicutes, Proteobacteria, Bacteroidetes, and Spirochaetes. B. zhangzhouensis and B. altitudinis could convert NH₄⁺-N to NO₃^--N, and A. pittii could transfer H₂S to SO₄^2-. This study revealed that bacteria deodorant can reduce the concentrations of NH₃, H₂S, and VFAs in pig feces and increase those of NH₄⁺, NO₃^-, and SO₄^2- and has excellent potential in deodorizing livestock and poultry feces composting.