Biofilms are a group of microorganism cells such as bacteria, alga, yeast or protozoa which stick to each other on a surface or interface and are protected in matrix of extracellular polymeric substance (EPS). Cells in biofilms have higher density and support each other in polluted-substance metabolism because they preserve moisture, salt concentration or oxidation-reduction potential between contiguous cells. Thus they create a special structure of biofilm and help them to control flowing circulation between cells. Therefore, the study on biofilm formed by microorganisms isolated from polluted areas enhances remediation of polluted matters. Eight bacterial strains were isolated from wastewater of Duc Giang petrol storage tank in Gia Lam districst, Hanoi via enrichment in liquid mineral medium supplemented with phenol as the only carbon and energy sources. Of the eight strains, three strains (DGP8, DGP2 and DGP4) have the best capacity of biofilm formation; therefore they were used to provide multi-species biofilm for further investigation. The results indicated that, biofilm formed by these strains could transform phenol at different concentration in the mineral medium, optimally at 150 mg/l phenol. HPLC analysis confirmed that phenol peak decreased gradually whereas new peaks with different retention times appeared over time, indicating the transformation of phenol to intermediate products. Quantitative analyses of the peaks showed that as much as 99,3 percent of phenol in the medium was removed after 7 day incubation (with 150 mg/l of initinal concentration). Thus, using multi-species biofilms for getting efficient and sustainable systems of phenol transformantion (and other pollutants as well) has promising application potentials.
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