(330e) Biodegradation of High Phenol Concentration in Wastewater by Pseudomonas Sp. Isolated From An Industrial Area

This study reports the successful isolation and characterization of a new phenol-degrading bacterium (Pseudomonas sp.) isolated from an industrial area in Cubatão-Brazil, using a culture enrichment technique. 16S rRNA gene sequence analysis revealed that strain belonged to the gamma group of Proteobacteria, with a 98.0% identity to 16S rRNA gene sequences of Pseudomonas aeruginosa (BLAST, GenBank, NCBI). It was Gram-negative, aerobic, mobile, urease and oxidase-positive. The above properties of strain are consistent with its classification within the genus Pseudomonas. Pseudomonas sp. could aerobically grow on a number of aromatic compounds, such as phenol, catechol and hydroquinone. The phenol degrading potential of the isolate was measured by inoculation of pure culture in the mineral medium containing various phenol concentrations ranging from 100 to 1800 mg/L in a batch reactor and monitoring phenol disappearance rate at regular intervals of time. Growth of the isolate in mineral medium with various phenol concentrations was monitored by measuring the turbidity (OD 600 nm) and the substrate consumption by HPLC. A prolonged lag phase, varying from 0 to 29 h, was observed, followed by an exponential biodegradation phase, in which the growth biomass and simultaneous transformation of phenol occurred. Finally, the curves showed a decline as the substrate was depleted. Bacterial growth was completely inhibited and no biodegradation was observed for a higher phenol concentration (above 2000 mg/L). This characteristic behavior can be explained by the increase in biomass and by self-inhibition. Once the lag phase was completed, significant increases in cell mass occurred. Because the substrate-utilization rate is proportional to the biomass concentration, the rate of substrate utilization accelerated during the test in response to increasing biomass. Biomass concentrations at the end of batch runs increased even after phenol was completely utilized. This phenomenon may be explained by the fact that phenol was first transformed into intermediate metabolites, not measured in this experiment, and these served as substrates until fully degraded. A typical example of a time-independent plot of biomass concentration versus phenol concentration was obtained. The biomass and phenol concentrations were linearly related for most of the active growth phase. Coefficients of correlation for all experiments were above 0.97, with the best phenol degradation rate value of 6.25 mg phenol/L/h utilized during the active growth period. A high growth until 600 mg/L of phenol is observed, but above this value, the phenol acts initially as inhibitor of growth. The best known phenol-tolerant bacterium described is Pseudomonas putida MTCC1194 which could tolerate phenol up to 1000 mg/L. In summary, we describe a novel high concentration phenol-degrading bacterium using a culture enrichment technique. These results demonstrate that this strain has a high level of tolerance to phenol toxicity, and it consequently has potential applications in the biotreatment of industrial wastewaters or in the in situ bioremediation of phenol-contaminated soils. Acknowledgements: FAPESP, INCT and CNPq.