Response of Syntrophic Propionate Degradation to pH Decrease and Microbial Community Shifts in an UASB Reactor

• Published in: Journal of microbiology and biotechnology Vol. 26; no. 8; pp. 1409 - 1419
• Main Authors: Zhang, Liguo, Ban, Qiaoying, Li, Jianzheng, Jha, Ajay Kumar
• Format: Journal Article
• Language: English
• Published: Korea (South) 한국미생물·생명공학회 28.08.2016
• Subjects: Anaerobiosis; Bacteria - classification; Bacteria - isolation & purification; Bacteria - metabolism; Bioreactors; Carbon - metabolism; DNA, Bacterial; Euryarchaeota - isolation & purification; Euryarchaeota - metabolism; Hydrogen-Ion Concentration; Microbial Consortia - physiology; Phylogeny; Propionates - analysis; Propionates - metabolism; RNA, Ribosomal, 16S - metabolism; Sewage - microbiology; Temperature; Waste Disposal, Fluid - methods; 생물학; PCR-DGGE; Upflow anaerobic sludge blanket reactor; pH decrease; microbial community structure; propionate degradation
• ISSN: 1017-7825; 1738-8872
• DOI: 10.4014/jmb.1602.02015

The effect of pH on propionate degradation in an upflow anaerobic sludge blanket (UASB) reactor containing propionate as a sole carbon source was studied. Under influent propionate of 2,000 mg/l and 35ºC, propionate removal at pH 7.5-6.8 was above 93.6%. Propionate conversion was significantly inhibited with stepwise pH decrease from pH 6.8 to 6.5, 6.0, 5.5, 5.0, 4.5, and then to 4.0. After long-term operation, the propionate removal at pH 6.5-4.5 maintained an efficiency of 88.5%-70.1%, whereas propionate was hardly decomposed at pH 4.0. Microbial composition analysis showed that propionate-oxidizing bacteria from the genera Pelotomaculum and Smithella likely existed in this system. They were significantly reduced at pH ≤5.5. The methanogens in this UASB reactor belonged to four genera: Methanobacterium, Methanospirillum, Methanofollis, and Methanosaeta. Most detectable hydrogenotrophic methanogens were able to grow at low pH conditions (pH 6.0-4.0), but the acetotrophic methanogens were reduced as pH decreased. These results indicated that propionate-oxidizing bacteria and acetotrophic methanogens were more sensitive to low pH (5.5-4.0) than hydrogenotrophic methanogens.