ENHANCEMENT OF POLYETHER BIODEGRADATION IN ACTIVATED-SLUDGE FOLLOWING EXPOSURE TO CONDITIONING AGENTS

Activated sludge exposed to C18 unsaturated fatty acid diesters of polyethylene glycol (PEG) acquires the ability to degrade PEG of average molecular weight (Mn) 1,000, 1,450, 3,350 but not 8,000. Likewise, a polypropylene glycol (PPG) diester of oleic acid enhances the degradation of PPG Mn 1,025. An analogous enhancement in PEG degradative activity is effected by pre-exposure to polyoxyethylene oleyl monoether. Enhancement of degradation is restricted to polyethers which are the same kind as used in the pretreatment; for example, samples pre-exposed to PEG unsaturated diester are unable to degrade PPG. Thin layer chromatographic analysis of PEG incubations indicates disappearance of PEGs from the supernatant without a noticeable change in the molecular weight of remaining PEGs. Removal of these compounds from the supernatants occurs well before catabolic CO2 evolution is completed. Since there were negligible increases in the biomass and acetylesterase activity resulting from the catabolism of PEG or its diester and minimal levels of C-14-assimilation from C-14-PEG, the responsible microbial populations are apparently not deriving growth or energetic benefits from the degradative process. A working model consistant with these findings assumes the polyethers are degraded by enzymes specific for other substrates, i.e., examples of cometabolism or fortuitous metabolism. It is proposed that degradation of recalcitrant pollutants could be enhanced by the addition of metabolizable derivatives of the pollutants (conditioning agents) to ecosystems.