SELECTION OF XENOBIOTIC-DEGRADING MICROORGANISMS IN A BIPHASIC AQUEOUS-ORGANIC SYSTEM

Microbial selection on mixtures of chlorinated and nonchlorinated comp ounds that are poorly soluble in water and/or toxic to growing microbi al cells was examined in both biphasic aqueous-organic and monophasic aqueous systems. A biphasic system in which silicone oil was used as t he organic phase permitted the acceleration of acclimation, leading to rapid selection and to an increase in xenobiotic compound degradation . In contrast, acclimation, selection, and degradation were very slow in the monophasic aqueous system. The variation in microbial growth ra te with the degree of dispersion (i.e., dispersion at different silico ne oil concentrations and agitation rates), and cell adhesion to the s ilicone oil indicate that the performance of the biphasic aqueous-orga nic system is dependent on the interfacial area between the two phases and that microbial activity is important at this interface. Therefore , the biphasic water-silicone oil system could be used for microbial s election in the presence of xenobiotic compounds that are toxic and ha ve low water solubility.