Single and multiple effects of organic solvents on the expression level of acetyl-CoA synthetase gene and active methanogenic population

Abstract

Bu çalışmada, laboratuvar ölçekli kesikli reaktörlerden alınan anaerobik çamurda metanol (0.1- 1.5 M), toluen (0.5 - 4.0 mM), iso-propanol (0.1- 2.0 M) ve toluen + methanol (0.5 mM + 1.0 M, 1.5 mM + 1.0 M)'in metan üretimine, asetil-KoA sentetaz geninin ekspresyon seviyesine ve mikrobiyal kommüniteye inhibitör etkisi incelenmiştir. Reaktörlerde artan konsantrasyonların biogaz üretimlerinde düşüşe sebep olduğu görülmüştür. En yüksek oranda inhibisyon etkisi sırasıyla iso-propanol ve toluen + metanol ile beslenmiş reaktörlerde görülmüştür. Methanosaeta'nın asetil-KoA sentetaz geni ekspresyon seviyesi metanol ve metanol + toluen eklenmiş çamurlarda aynı kalırken, toluen ve iso-propanol eklenmiş çamurlarda gen ekspresyonu tespit edilememiştir.Artan konsantrasyonlar aktif mikrobiyal populasyon yüzdesinde ise artışlara sebep olmuştur. Reaktörlerde genellikle baskın türün Methanosaeta olduğu tespit edilmiştir. Methanosaeta populasyonunu yüksek konsantrasyonlu solventlere dayanıklı olduğu görülen ve toluen eklenen reaktörde en baskın tür olduğu gözlenen Methanobacteriales izlemiştir.

In this study, effects of solvents such as methanol (0.1-1.0 M), toluene (0.5- 4.0 mM), iso-propanol (0.1-2.0 M) and toluene + methanol (0.5 mM + 1.0 M, 1.5 mM + 1.0 M) on methane production, expression level of acetly-CoA synthetase gene and viable microbial populations were studied in sludges taken from batch reactors. Within the scope of this study, it was found that biogas productions of the reactors decreased with increasing concentrations of the solvents. The most severe effects of solvents were observed for the iso-propanol and toluene + methanol added reactors, respectively. It was also found that the expression of acetyl-CoA synthetase genes of Methanosaeta remained quite unchanged after exposures to methanol and methanol + toluene added reactors whereas no expression was detected for toluene and iso-propanol added reactors.The percentage of active microbial populations generally increased by the increasing concentrations of solvents. Methanosaeta usually dominated in the reactors. The dominance of Methanosaeta was followed by Methanobacteriales which was usually resistant to higher concentrations and observed to be dominating genus in toluene added reactor.