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To clarify the effect of propionate concentration on propionate degradation, propionate degradation feature at different propionate concentration conditions was investigated. A mesophilic syntrophic propionate-oxidizing bacterial community (containing propionate-oxidizing bacteria and methanogens) was firstly obtained by 15 times subculture using propionate as sole carbon source. Polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) revealed that the main propionate-oxidizing bacteria belonged to genus Syntrophobacter while hydrogenotrophic methanogens and aceticlastic methanogens were related to Methanobacterium and Methanosaeta, respectively. Then the batch test was performed for evaluating the effect of propionate concentration on syntrophic propionate degradation. The results showed that the propionate was rapidly degraded at propionate concentration of 1 000-2 000 mg/L tinder the inoculated sludge of 0. 81 g/L condition. However, the propionate degradation was inhabited when the propionate concentration was 2 500-3 000 mg/L. The inhibition was gradually relieved with extension of time. It implied that high concentration propionate (≥ 2 500 mg/L) would inhibit the metabolic activity of propionate-oxidizing bacteria and this inhibition was reversible. [ABSTRACT FROM AUTHOR]