Autochthonous bioaugmentation with non-direct degraders: A new strategy to enhance wastewater bioremediation performance

Autochthonous bioaugmentation (ABA) strategies are primarily carried out using a single, highly efficient type of bacteria that is capable of directly degrading the target compound. However, no studies have examined the use of non-direct degraders (NDDs), which are involved in the metabolic pathway of target compounds instead of direct degradation. Here, to evaluate the bioremediation efficiency and mechanism of ABA by NDDs, we demonstrated the use of an NDD on the biodegradation of biphenyl, a model compound used to study polychlorinated biphenyl (PCB) degradation. The NDD examined in this study, Marmoricola LJ-33, was isolated from activated sludge. Although Marmoricola LJ-33 alone did not directly degrade biphenyl under laboratory conditions, it did contribute to in situ biphenyl biodegradation in the activated sludge, as evidenced by DNA-stable-isotope-probing (DNA-SIP). Implementation of ABA with strain LJ-33 was shown to significantly accelerate biphenyl degradation efficiency, demonstrating the potential of NDD strains for degradation in ABA. More importantly, LJ-33 amendment altered the diversity of the microbial communities involved in biphenyl metabolism. Our findings suggest that a combination of pre-screening followed by DNA-SIP analysis is a practical strategy to precisely separate NDDs. Additionally, our work indicates a new mechanism of ABA strategy with NDDs as a promising in situ bioremediation strategy, broadening our concept in constructing functional consortia to enhance the biodegradation performance of activated sludge in wastewater treatment plants.