Biodegradation of xylene and butyl acetate using an aqueous-silicon oil two-phase system

A stable microbial population, consisting of seven bacterial strains and th ree yeast strains, was selected in batch cultures on a mixture of ortho and meta-xylene and butyl acetate as the sole source of carbon and energy. Thi s population can completely degrade up to 10 g/L of a mixture of these xeno biotics (70% xylene and 30% butyl acetate wt/wt) in a two-phase aqueous-sil icone oil system (70%/30% vol/vol) within 96 h, while for the usual one-pha se system very low growth degradation rates were observed. Further organic solvents were tested and finally, silicon oil was selected as the best orga nic phase for such a two-phase system. With periodical pH adjustments to 6. 0 in fed-batch mode, the culture showed a global degradation rate of 63 mg L-1 h(-1).