Altered active pyrene degraders in biosurfactant-assisted bioaugmentation as revealed by RNA stable isotope probing

Bioaugmentation is an effective approach for removing pyrene from contaminated sites, and its performance is enhanced by a biosurfactant. To reveal the mechanisms of biosurfactant-assisted bioaugmentation, we introduced RNA stable isotope probing (RNA-SIP) in the pyrene-contaminated soils and explored the impacts of rhamnolipid on the pyrene degradation process. After 12-day degradation, residual pyrene was the lowest in the bioaugmentation treatment (7.76 ± 1.57%), followed by biosurfactant-assisted bioaugmentation (9.86 ± 2.58%) and enhanced natural attenuation (23.97 ± 1.05%). Thirteen well-known and two novel pyrene-degrading bacteria were confirmed to participate in the pyrene degradation. Pyrene degradation was accelerated in the biosurfactant-assisted bioaugmentation, manifested by the high diversity of active pyrene degraders. Our findings expand the knowledge on pyrene degrading bacteria and the mechanisms of pyrene degradation in a bioaugmentation process.