Aerobic cometabolism of 1,1,2,2-TeCA by a propane-growing microbial consortium (C2): Diversity of alkane monooxygenase genes and design of an on-site bioremediation process

- The microbial consortium C2 has the unique feature to co-metabolize TeCA under aerobic conditions.
- Genes encoding alkane MOs belonging to AlkB, SDIMO and cytochrome P450 were characterized in C2.
- Different bioreactor configurations were tested for the treatment of TeCA contaminated groundwater with C2.
- A continuous stirred-tank reactor (CSTR) followed by a plug-flow reactor (PFR) gave the best performance.

Microbial degradation of 1,1,2,2-tetrachloroethane has been rarely analysed under aerobic conditions. In this work, the catabolic potential of a TeCA-degrading aerobic propanotroph consortium (C2) and the optimal bioreactor configuration for an on-site TeCA-bioremediation strategy with C2 were defined. More specifically, the diversity of alkane-oxidizing bacteria in C2 was assessed by means of clone libraries of genes coding for alkane monooxygenases (MOs) of different families (AlkB-like alkane hydroxylase, soluble di-iron MO and cytochromes P450). A large number of alkane MO sequences retrieved in this study showed the highest similarity with reference sequences belonging to Rhodococcus genus, suggesting a key role of this genus in TeCA/propane co-metabolism, while the remaining alkane MO sequences were mainly attributed to other Actinobacteria, to Bradhyrizobiaceae, and Cupriavidus genus. Further, the feasibility of an on-site TeCA bioremediation strategy with C2 was evaluated by simulating a continuous-flow aerobic co-metabolic process with different bioreactor configurations. Our results show that the configuration with a suspended-cell continuous stirred-tank reactor (CSTR) followed by a suspended-cell plug-flow reactor (PFR) was the one giving the best performance with consortium C2.