ENHANCED DEGRADATION OF POLYCHLORINATED-BIPHENYLS BY DIRECTED EVOLUTION OF BIPHENYL DIOXYGENASE

Biphenyl dioxygenases (BP Dox) from different organisms, which are inv olved in the initial oxygenation and subsequent degradation of polychl orinated biphenyls (PCB), are similar in structure but have different functions. The large subunit of Up Dox, encoded by the bphA1 gene, is crucial for substrate selectivity. Using the process of DNA shuffling, we randomly recombined the bphA1 genes of Pseudomonas pseudoalcaligen es KF707 and Burkholderia cepacia LB400 and selected for genes that ex pressed proteins with altered function. Upon expression in Escherichia coli, some of these evolved genes exhibited enhanced degradation capa city, not only for PCB and related biphenyl compounds, but for single aromatic hydrocarbons such as benzene and toluene, which are poor subs trates for the original BP Dox.