The present study investigated the effect of ammonia load on microbial communities in mesophilic anaerobic digestion of propionic acid. A laboratory-scale continuous anaerobic digester treating propionic acid as a sole organic substrate was operated under non-inhibitory condition and inhibitory conditions with ammonia (1.5 g and 3.5 g ammonia-N/L, respectively), and bacterial and archaeal communities in the steady states of each ammonia condition were analyzed using high-throughput sequencing. Thirteen bacterial families were detected as abundant bacterial groups in mesophilic anaerobic digestion of propionic acid. Increase in ammonia concentration resulted in significant shifts in microbial community structures. Syntorophobacter, Pelotomaculum, and Thermovigra were determined as the dominant groups of (potential) propionate oxidizing bacteria in the non-inhibitory condition, whereas Cryptanaerobacter and Aminobacterium were the dominant groups of (potential) propionate oxidizing bacteria in the ammonia-inhibitory condition. Methanoculleus and Methanosaeta were the dominant methanogens. Acetate-oxidation coupled with hydrogenotrophic methanogenesis might be enhanced with increases in the relative abundances of Methanoculleus and Tepidanaerobacter acetatoxydans under the ammonia-inhibitory condition. The results of the present study could be a valuable reference for microbial management of anaerobic digestion systems that are exposed to ammonia inhibition and propionic acid accumulation.

Abstract
1. 서 론
2. 재료 및 방법
    2.1. 재료
    2.2. 연구방법
3. 결과 및 고찰
    3.1. 차세대염기서열분석 결과
    3.2. 암모니아 부하에 따른 프로피온산 혐기성 소화 공정 미생물 종 다양성 분석
    3.3. 암모니아 부하에 따른 프로피온산 혐기성 소화 공정 미생물 군집 구조 분석
4. 결 론
REFERENCES

• Le Thi Nhu Trang(부경대학교 지구환경시스템과학부(환경공학전공))
• 이준엽(부경대학교 환경공학과) | Joonyeob Lee (Department of Environmental Engineering, Pukyong National University) Corresponding author