Bioaugmentation of activated sludge by an indigenous 3-chloroaniline-degrading Comamonas testosteroni strain, I2gfp

A strain identified as Comamonas testosteroni 12 was isolated from activate d sludge and found to be able to mineralize 3-chloroaniline (3-CA), During the mineralization, a yellow intermediate accumulated temporarily, due to t he distal mete-cleavage of chlorocatechol. This strain was tested for its a bility to clean wastewater containing 3-CA upon inoculation into activated sludge. To monitor. its survival, the strain was chromosomally marked with the gfp gene and designated I2gfp, After inoculation into a lab-scale semic ontinuous activated-sludge (SCAS) system, the inoculated strain maintained itself in the sludge for at least 45 days and was present in the sludge flo cs, After an initial adaptation period of 6 days, complete degradation of 3 -CA was obtained during 2 weeks, while no degradation at all occurred in th e noninoculated control reactor, Upon further operation of the SCAS system, only 50% 3-CA removal was observed, Denaturing gradient gel electrophoresi s (DGGE) of 16S rRNA genes revealed a dynamic change in the microbial commu nity structure of the activated sludge, The DGGE patterns of the noninocula ted and the inoculated reactors evolved after 7 days to different clusters, which suggests an effect of strain inoculation on the microbial community structure. The results indicate that bioaugmentation, even with a strain or iginating from that ecosystem and able to effectively grow on a selective s ubstrate, is not permanent and will probably require regular resupplementat ion.