Fungal metabolism of toluene: Monitoring of fluorinated analogs by F-19 nuclear magnetic resonance spectroscopy

We used isomeric fluorotoluenes as model substrates to study the catabolism of toluene by five deuteromycete fungi and one ascomycete fungus capable o f growth on toluene as the sole carbon and energy source, as well as by two fungi (Cunninghamella echinulata and Aspergillus niger) that cometabolize toluene, Whole cells were incubated with 2-, 3-, and 4-fluorotoluene, and m etabolites were characterized by F-19 nuclear magnetic resonance. Oxidation of fluorotoluene by C. echinulata was initiated either at the aromatic rin g, resulting in fluorinated omicron -cresol, or at the methyl group to form fluorobenzoate. The initial conversion of the fluorotolueues by toluene-gr own fungi occurred only at the side chain and resulted in fluorinated benzo ates. The latter compounds were the substrate for the ring hydroxylation an d, depending on the fluorine position, were further metabolized up to catec holic intermediates. From the F-19 nuclear magnetic resonance metabolic pro files, we propose that diverse fungi that grow on toluene assimilate toluen e by an initial oxidation of the methyl group.