Expression and longevity of toluene dioxygenase in Pseudomonas putida F1 induced at different dissolved oxygen concentrations

Toluene dioxygenase (TDO) in Pseudomonas putida F1 (PpF1) was used as a model to determine if enzymes that initiate aerobic BTEX degradation can be expressed at very low dissolved oxygen (DO) concentrations. Emphasis was placed on characterizing how the DO concentration during induction affects the level of enzyme expression. TDO was expressed at similar levels in PpF1 cells induced on toluene at different DO concentrations (ca. 1, 4, and 8 mg L−1). TDO activity decayed exponentially with cell age at 0.25–0.48 day−1. Nevertheless, the DO concentration during induction did not significantly affect TDO expression or longevity. PpF1 also grew on toluene at 0.1 mg L−1 DO, showing that TDO can be expressed at very low DO levels. This suggests that aerobic biotransformations are likely to contribute to BTX bioremediation even when an aerotolerant anaerobic respiration mode (e.g., denitrification) is prevalent.