Microbial Community Composition and Response to Temperature Shock of a Mesophilic Propionate-degrading Methanogenic Consortium

In this study, a mesophilic propionate-degrading methanogenic community was obtained by subculture of anaerobic sludge from an anaerobic baffled reactor, using propionate as sole carbon source. The microbial community composition of the enriched culture was examined by polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) based on 16S rRNA gene partial sequences. The result revealed that two major bands (B1 and B2) had a high similarity with the identified POB in genus Syntrophobacter. While Methanobacterium and Methanothrix were dominant methanogens in the enriched culture. They formed a great syntrophic relationship with specific COD_pro removal rate of sludge and specific methane production rate of sludge were 0.6 kg/(kg MLVSS d) and 280 L/(kg MLVSS d), respectively. In view of microbial metabolism would be significantly affected by temperature, response of the propionate enriched culture on temperature shocks was investigated. At the optimum temperature (35°C~40°C), propionate was degraded completely after 5-day cultivation. Temperature shocks, from 35°C to 30°C, 25°C, 20°C, resulted in propionate removal rate was decreased instantaneously. However, propionate removal rate was recovered to the value at 35°Cafter 2~3 days adaptation, indicating this propionate-degrading methanogenic community had a strong resistance to temperature fluctuation.