## 2 Materials and Methods
### Preparation of Odor-Degrading Microbial Consortium (Isolation and Screening)  
The ammonia-degrading bacteria were isolated from swine manure waste collected from Yongin, Korea. Ammonia-degrading bacteria were isolated using a modified culture method in Transwell plates containing R\({}_{2}\)A, MRS, and Sabouraud media. Microorganisms were enriched in a Transwell plate containing 1 g of soil or manure and 3 mL of R\({}_{2}\)A, MRS (for bacteria), and Sabouraud (for yeasts) medium. After culturing for 2 weeks at 28 \({}^{\circ}\)C, the culture was serially diluted, and 100 \(\mu\)L of each dilution was spread on R\({}_{2}\)A, MRS, and Sabouraud agar plates. Colonies were selected and streaked separately on media plates until pure colonies were obtained, following which, they were sub-cultured for an odor degradation test and stored at \(-\)70 \({}^{\circ}\)C in media broth supplemented with 20% (\(v/v\)) glycerol.  
The ability of each bacterial strain to oxidize ammonium into nitrite was determined by a colorimetric method using Griess reagent and was subsequently screened. Among several strains (52 strains) identified, 16 strains were selected depending on their nitrification ability. Among them, strains with an enhanced ability to reduce NH\({}_{3}\) gas were re-screened using colorimetric Gastec tubes (Gastec Inc., Tokyo, Japan), where the NH\({}_{3}\) concentration ranged from 10 to 1000 ppm.  
Screening was performed in 250 mL Erlenmeyer flasks containing tissue papers wetted with NH\({}_{3}\) solution. The bacterial isolates were spiked onto NH\({}_{3}\) tissue. Each flask was tightly sealed and left undisturbed for degradation. Degradation experiments were conducted under a closed system at ambient room temperature (22 \({}^{\circ}\)C) and 30 \({}^{\circ}\)C. NH\({}_{3}\) tissue was spiked with 10 mL of bacterial solution. The NH\({}_{3}\) gas concentration was measured at different time intervals (0, 1, 12, 24, 36, and 48 h). Finally, three bacterial strains with enhanced NH\({}_{3}\) reduction abilities were selected for further experiments.  
The strains were chosen on the basis of their maximum effectiveness in the removal of ammonia and the influence of surfactant foam on their growth. The 16S rRNA gene of bacteria was amplified by using PCR (Bio-Rad, Hercules, CA, USA) with forward and reverse primers 27F and 1492R, respectively, and the 18S rRNA gene of yeast was amplified by using PCR (Bio-Rad, Hercules, CA, USA) with forward and reverse primers 1S1 and 18S, respectively. After sequencing, all the 16S rRNA and 18S rRNA gene sequences of phylogenetically closest neighbors were identified and retrieved from the EzBioCloud server ([[https://www.ezbiocloud.net/identify](https://www.ezbiocloud.net/identify)]([https://www.ezbiocloud.net/identify](https://www.ezbiocloud.net/identify)), accessed on 1 December 2021) and NCBI GenBank database ([[https://blast.ncbi.nlm.nih.gov/Blast.cgi](https://blast.ncbi.nlm.nih.gov/Blast.cgi)]([https://blast.ncbi.nlm.nih.gov/Blast.cgi](https://blast.ncbi.nlm.nih.gov/Blast.cgi)), accessed on 1 December 2021), respectively.  
The three efficient NH\({}_{3}\)-degrading strains selected from the closed system were mixed at an equal ratio (1:1:1), and NH\({}_{3}\) reduction was conducted again under the open system. The NH\({}_{3}\) tissue was spiked with a solution of the microbial consortium (10 mL). The NH\({}_{3}\) gas concentration in the open flask was determined at different time intervals (0, 1, 12, 24, 36, and 48 h).