Microbial characterization and quantification of an anaerobic sludge degrading dimethyl phthalate

Characterization and quantification of microbial community in dimethyl phthalate (DMP)-degrading anaerobic sludge using molecular techniques.

An enriched anaerobic sludge effectively degrading over 99% of dimethyl phthalate in an upflow anaerobic sludge blanket (UASB) reactor for 530 days was characterized and quantified by 16S rRNA-based molecular methods. A total of 78 Bacteria clones were classified into 22 operational taxonomic units (OTUs) in nine divisions, including Firmicutes, Proteobacteria, Chloroflexi, Thermotogae, Bacteroidetes/Chlorobi, Spirochaetes, Acidobacteria and two candidate divisions. The two most abundant OTUs were likely responsible, respectively, for the de-esterification of DMP and the subsequent phthalate degradation. The outer layer of the granule was dominated by Bacteria; whereas the interior was by Archaea, of which 89 +/- 5% were acetoclastic Methanosaetaceae and 11 +/- 5% hydrogenotrophic Methanomicrobiales.

Twenty-two Bacteria OTUs in DMP-degrading anaerobic sludge distributed in nine divisions. The two most abundant OTUs were likely responsible respectively for the de-esterification of DMP and the subsequent phthalate degradation. Layered granular microstructure of DMP-degrading anaerobic sludge suggested that the rate of DMP de-esterification is faster than its inward diffusion rate.

This work is the first study to characterize and quantify the microbial community in the anaerobic phthalic ester degrading sludge from the anaerobic reactor.