Minkyung Song

Methanogenic population dynamics assessed by real-time quantitative PCR in sludge granule in upflow anaerobic sludge blanket treating swine wastewater

A pilot-scale upflow anaerobic sludge blanket (UASB) treating swine wastewater was operated for 382 days to evaluate the process performance and methanogenic population dynamics. A real-time quantitative PCR (QPCR) was used to detect and quantify the 16S rRNA gene concentrations of the domain Archaea, the four methanogenic orders, and the two aceticlastic families. Extended intervals of consistently stable and efficient wastewater treatment with a final hydraulic retention time (HRT) of 3.5 days were sustained. A high abundance of hydrogenotrophic methanogens was observed, with Methanobacteriales as the major group, suggesting that hydrogenotrophic methanogenesis, with the syntrophic oxidation of volatile fatty acids (VFAs), was a major route of methane formation. This phenomenon was mainly attributed to the high ammonium concentration in swine wastewater, which has a severe inhibitory effect mainly on aceticlastic methanogens. Although there was no significant growth of Methanosaetaceae, its abundance contributed to the formation and maintenance of granule.

Effects of prolonged starvation on methanogenic population dynamics in anaerobic digestion of swine wastewater

This study investigated the relationship between the processes and microbial populations induced by long-term starvation. To demonstrate the effects of starvation, a laboratory-scale anaerobic reactor was operated in three phases (first reaction, starvation, second reaction) for 316 days. During the first reaction, the chemical oxygen demand (COD) concentration decreased by about 70% of the input swine wastewater and 64L of methane gas was produced; during the second reaction, there was a 63% COD reduction and 36L of methane was produced. The methanogenic diversity, qualitatively monitored with denaturing gradient gel electrophoresis using archaeal 16S rRNA gene primers, was not different between two reactions. However, DNA copy numbers of Methanosarcinales, quantitatively monitored with quantitative real-time polymerase chain reaction using order-level 16S rRNA gene primers, showed the changed results. Cell numbers of Methanosarcinales and methanogenic activity were important factors determining the different efficiencies of the process.

Response surface analysis of solid state growth of Pleurotus ostreatus mycelia utilizing whey permeate

A novel approach to utilizing whey permeate, the cultivation of mycelia of the edible mushroom Pleurotus ostreatus, is introduced. Response surface analysis (RSA) was successfully applied to determine the combination of substrate concentration, temperature and pH that would result in a maximal mycelial extension rate under solid state cultivation. The conditions to maximize the mycelial extension rate were predicted to be 44 g lactose l−1, pH 6.0 and 24.2 °C. Subsequent verification of these levels agreed with model predictions.