Effect of temperature on performance and microbial community of thermophilic methane fermentation of kitchen waste

The study aimed to investigate the effect of temperature on performance and microbial community of thermophilic methane fermentation of kitchen waste. Kitchen waste was treated using a completely stirred tank reactor(CSTR) at 53°C and 60°C. Microbial community structure during treatment was analyzed using T-RFLP and 16 S rRNA clone library methods. At the temperature of 53°C and a VTS loading rate of 4 g/L/d, the treatment was stable without accumulation of VFA, with gas production approximately 900 mL/g-VTS. When the temperature was raised to 60°C, TOC and VFA accumulated sharply and the gas production decreased, with changes in both bacterial community and archaeal community. At 53 °C, the acidproducing fermenting bacteria were dominant. When the temperature was increased to 60°C, however, the population of fatty acid-oxidizing, especially acetate-oxidizing bacteria increased significantly. The population of aceticlastic methanogen Methanosarcina decreased while hydrogenotrophic methangen Methanothermobacter increased at 60°C. The main pathway of methane production from acetate at 60°C was through the acetate oxidization followed by hydrogenotrophic methanogenesis, which needs syntrophism of acetate-oxidizing bacteria and hydrogenotrophic methangens. The results showed that the operational temperature of 53°C is suitable for thermophilic methane fermentation of kitchen waste. Increase of operational temperature to 60°C would result in decrease of methane production through aceticlastic methanogenesis pathway, leading to accumulation of VFAs and deterioration of treatment.