Wautersia eutropha 自營脫氮及合成PHB最適培養條件之研究

Abstract

This study is to investigate the relationship between denitrification and behaviors of PHB accumulation by Wautersia eutropha in autotrophic systems. This study concluded that Wautersia eutropha accumulate PHB by a significant amount under both aerobic and anoxic conditions. This research based on batch experiments with membrane-feeding substrate bioreactor (MFSB) and serum bottles shows that Wautersia eutropha proceed two-stage denitrification which with nitrite as an intermediate by using hydrogen as a energy source and bicarbonate as a carbon source. It was also observed that Wautersia eutropha utilize PHB prior as a carbon source during denitrification reactions, which lowers the PHB level in cells. The largest accumulated amount of PHB in this study is 5.7 % of the dry weight of cells, however, much smaller than those with heterotrophic incubations. When the hydrogen supplied was stopped at the end of the denitrification reaction, Wauterrsia eutropha used PHB instead of accumulating it. As soon as the hydrogen returned to system, Wautersia eutropha immediately went back to accumulate PHB. The system achieves highest nitrate removal and PHB accumulation at a C/N ratio of 1.0 and both nitrate and bicarbonate concentration are set to be 300 mg/l. In this given condition, the specific denitrification rate is 0.15 mg-N/day/mg-biomass, and the specific PHB accumulated rate is 0.002 mg-PHB/day/mg-biomass, also, the PHB accumulation shows no connections to nitrate and bicarbonate levels at this study. The results of this study also suggest that ammonia, which raise the specific denitrification and the specific PHB accumulation, is a better nitrogen source than nitrate and nitrite for incubation of Wautersia eutropha.