Oxygenation reactions of various tricyclic fused aromatic compounds using Escherichia coli and Streptomyces lividans transformants carrying several arene dioxygenase genes

Bioconversion (biotransformation) experiments on arenes (aromatic compounds ), including various tricyclic fused aromatic compounds such as fluorene, d ibenzofuran, dibenzothiophene, carbazole, acridene, and phenanthridine, wer e done using the cells of Escherichia coli transformants expressing several arene dioxygenase genes. E. coli carrying the phenanthrene dioxygenase (ph dABCD) genes derived from the marine bacterium Nocardioides sp. strain KP7 converted all of these tricyclic aromatic compounds, while E. coli carrying the Pseudomonas putida F1 toluene dioxygenase (todC1C2BA) genes or the P. pseudoalcaligenes KF707 biphenyl dioxygenase (bphA1A2A3A4) genes was not ab le to convert these substrates. Surprisingly, E. coli carrying hybrid dioxy genase (todC1::bphA2A3A4) genes with a subunit substitution between the tol uene and biphenyl dioxygenases was able to convert fluorene, dibenzofuran, and dibenzothiophene. The cells of a Streptomyces lividans transformant car rying the phenanthrene dioxygenase genes were also evaluated for bioconvers ion of various tricyclic fused aromatic compounds. The ability of this acti nomycete in their conversion was similar to that of E. coli carrying the co rresponding genes. Products converted from the aromatic compounds with thes e recombinant bacterial cells were purified by column chromatography on sil ica gel, and identified by their MS and H-1 and C-13 NMR analyses. Several products, e.g., 4-hdroxyfluorene converted from fluorene, and cis-1,2-dihyd roxy-1,2-dihydrophenanthridine, cis-9,10-dihydroxy-9,10-dihydrophenanthridi ne, and 10-hydroxyphenanthridine, which were converted from phenanthridine, were novel compounds.