title: Response of Syntrophic Propionate Degradation to pH Decrease and Microbial Community Shifts in an UASB Reactor.
abstract: 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.
authors.affiliation: State Key Laboratory of Urban Water Resource and Environment, School of Municipal and Environmental Engineering, Harbin Institute of Technology, Harbin 150090, P.R. China.|College of Environmental and Resource Sciences, Shanxi University, Taiyuan 030006, P.R. China.
authors.forename: Liguo
authors.initials: L
authors.lastname: Zhang
authors.affiliation: College of Environmental and Resource Sciences, Shanxi University, Taiyuan 030006, P.R. China.
authors.forename: Qiaoying
authors.initials: Q
authors.lastname: Ban
authors.affiliation: State Key Laboratory of Urban Water Resource and Environment, School of Municipal and Environmental Engineering, Harbin Institute of Technology, Harbin 150090, P.R. China.
authors.forename: Jianzheng
authors.initials: J
authors.lastname: Li
authors.affiliation: Central Campus Pulchowk, Institute of Engineering, Tribhuvan University, Lalitpur 44700, Nepal.
authors.forename: Ajay Kumar
authors.initials: AK
authors.lastname: Jha
mesh_terms: D000693:Anaerobiosis; D001419:Bacteria / Q000145:classification / Q000302:isolation & purification / Q000378:metabolism; D019149:Bioreactors; D002244:Carbon / Q000378:metabolism; D004269:DNA, Bacterial; D019605:Euryarchaeota / Q000302:isolation & purification / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D059013:Microbial Consortia / Q000502:physiology; D010802:Phylogeny; D011422:Propionates / Q000032:analysis / Q000378:metabolism*; D012336:RNA, Ribosomal, 16S / Q000378:metabolism; D012722:Sewage / Q000382:microbiology; D013696:Temperature; D014865:Waste Disposal, Fluid / Q000379:methods
chemical_list: D004269:DNA, Bacterial; D011422:Propionates; D012336:RNA, Ribosomal, 16S; D012722:Sewage; D002244:Carbon
keywords: PCR-DGGE; Upflow anaerobic sludge blanket reactor; microbial community structure; pH decrease; propionate degradation