INTERFACIAL AREA EFFECTS OF A BIPHASIC AQUEOUS-ORGANIC SYSTEM ON GROWTH KINETIC OF XENOBIOTIC-DEGRADING MICROORGANISMS

The activity of xenobiotic-degrading microorganisms is generally high in a biphasic aqueous/organic system, Therefore, the influence of inte rfacial area variation on kinetic parameters of Candida sp. growing on ethyl butyrate was evaluated. Interfacial areas of both aseptic and c ultured biphasic systems were utilized. Substrate transport measuremen ts in aseptic system (where the interface varied with the organic-phas e fraction and agitator speed) showed that the substrate concentration in the aqueous phase was constant at different agitation speeds and d ecreased as the organic phase increased. Kinetic measurements of the c ultured system showed that kinetic parameters vary as functions of the ir respective aseptic interfacial areas. Higher mu(max) and K-i and lo wer K-s values were obtained with larger interfacial areas. Measuremen ts of the cultured system showed that the interfacial area increased a s the biomass increased, and that about 50% of the biomass was attache d to the interface as an interfacial biofilm at the end of the culture . Results suggest that the growth and selection of xenobiotic-degradin g microorganisms in a biphasic aqueous/organic system should be evalua ted mainly on the basis of the activity of adhering biomass (forming a biofilm) at the interfacial area rather than on substrate transport t o the aqueous phase