CELL HYDROPHOBICITY INFLUENCING THE ACTIVITY STABILITY OF XENOBIOTIC-DEGRADING MICROORGANISMS IN A CONTINUOUS BIPHASIC AQUEOUS-ORGANIC SYSTEM

Cell hydrophobicity effects on the activity/stability of microorganism s of a mixed culture, selected on 2,4,6-trichlorophenol (2,4,6-TCP) in both biphasic aqueous-silicone oil and monophasic aqueous continuous systems was determined. The mixed culture composed of Pseudomonas, str ains SP1 and SP2, Arthrobacter sp. AR2 and Alcaligenes sp. AL2 was cul tured at dilution rates from 0.033 to 0.22 h(-1). High dilution rates permitted the selection of Pseudomonas cells in both systems, with a h igher cell concentration in biphasic system. Selected cells proportion with a high cell adhesion capacity increased as a function of the cel l hydrophobicity, which was high at high dilution rates. The degradati on rate which also increased as a function of the dilution rate in bot h systems, was about two times higher in the biphasic system than in m onophasic one. The results indicate that the cell hydrophobicity, whic h increases with the growth rate, is a key factor in the selection and activity of xenobiotic-degrading microorganisms. Therefore, microbial selection and xenobiotics biodegradation at high dilution rates could be favored in reactors containing solid or liquid surfaces.