Degradation of phenol in activated sludge

BASILE LA, FIGUEROLA E, ERIJMAN L.

Pinamar

Congreso; XLI Reunión anual – Sociedad argentina de investigaciones en bioquímica y biología molecular (SAIB); 2005

SAIB

We have analyzed the enrichment of microorganisms involved in the biodegradation of phenol in activated sludge. Four sequential batch laboratory scale reactors were supplied with saline medium, yeast extract and peptone. Two of the reactors received additionally 80 mg of phenol per day. Time-dependent changes in the structure of microbial communities were analyzed by RT-PCR coupled to denaturing gradient gel electrophoresis (DGGE). Whereas the rate of phenol degradation evaluated in batch assays was 10 folds greater in treated reactors sludges compared to control reactors, banding patterns of treated and control reactors (of both rDNA and rRNA) were not significantly different. A quantitative real time PCR detection system was developed for the different subclasses of the major subunit of phenol hydroxylase enzyme (LmPH) genes, previously described as high, medium and low media saturation constant (Ks). The number of total copies of LmPH gene (per mg of MLSS) was (1.3+0.1) x109 and (3.2+0.4) x109 for the treated reactors, and (7.3+1.6) x107 and (1.6+0.1) x108 for the control reactors. Assuming a single copy of LmPH gene/cell, these values represent 8.1% of total bacteria in the treated reactors and only 1.0% in the controls (p<<0.001). The real time PCR assay revealed the enrichment in phenol degraders through the increase in the number of genes of low Ks and high Ks in phenol-amended reactors, allowing the detection of functional differences between communities, which were not evidenced by DGGE.