ACCELERATING DETOXIFICATION BY MANIPULATING INTRACELLULAR ELECTRON CARRIERS

摘要

This research sets out to show that a two-stage treatment system can accelerate thernremoval of organic contaminants whose first biodegradation step is arnmonooxygenation reaction. Monooxygenations require dissolved oxygen (DO) and arnreduced electron carrier, such as NADH+H~+, as cosubstrates. In the two-stagernprocess, biomass is recycled between a small accelerator tank, which also receivesrnthe influent, and a large aerator tank. The accelerator tank creates a specialrnenvironment that should increase the overall rate of monooxygenation.rnAn experimental comparison of the two-tank accelerated system to a one-tank systemrndocumented that the two-tank system was more efficient than the one-tank system atrnremoving phenol and 2,4-dichlorophenol (DCP), substrates requiring an initialrnmonooxygenation. The rates of the monooxygenation reactions were increased in thernaccelerator tank, and this led to improved overall removals compared to a one-tankrnsystem.rnWithin the accelerator tank, the NADH+H~+ content of the cells increased as the DOrnconcentration decreased. Since NADH+H~+ is a cosubstrate for monooxygenationrnreactions, they were accelerated by the increasing NADH+H~+ levels. However, thernconcentration of NADH+H~+ in the accelerator was, on average, lower than in thernaerator. The specific growth rates in the accelerator were substantially higher than inrnthe aerator. Although the high growth rate was responsible for the lower NADH+H~+rnlevels, it also was proportional to the cell抯 content of the monooxygenase. Even whenrnthe NADH+H~+ level was reduced in the accelerator, the rate of monooxygenation wasrnincreased by the high level of the monooxygenase.