METABOLISM OF HALOGENATED COMPOUNDS IN THE WHITE-ROT FUNGUS BJERKANDERA-ADUSTA STUDIED BY MEMBRANE INLET MASS-SPECTROMETRY AND TANDEM MASS-SPECTROMETRY

Membrane inlet mass spectrometry has been used for the characterizatio n of halogenated organic compounds produced by the fungus Bjerkandera adusta. Using this technique we obtained electron impact-, chemical io nization-, electron capture negative chemical ionization-mass spectra and tandem mass spectra directly from the growth medium. Through this direct analysis of the samples we identified novel bioconversion produ cts and confirmed recently published data on the production of both ch lorinated and brominated methoxybenzaldehyde metabolites. Growth profi les of the culture grown on a defined medium showed that the productio n of secondary metabolites starts after approximately 6 days and reach es maximal concentrations of 25-250 mu M after 15-20 days. Although de layed, the production of secondary metabolites paralleled a depletion of glucose from the medium acid stopped shortly after all glucose had been consumed. Experiments in which fluoro- and bromo-labeled 4-methox ybenzaldehydes were added to the medium at day 8 showed biotransformat ion of these compounds into chloro-3-fluoro-4-methoxybenzaldehyde and chloro-3-bromo-4-methoxybenzaldehyde, respectively. No dichlorinated p roducts were observed, suggesting that halogenation takes place only a t the meta position on the 4-methoxybenzaldehydes. These experiments a re the first to bring direct evidence of a halogenation mechanism, wh ere the enzymatic attack takes place directly on the 4-methoxybenzalde hyde intermediates. (C) John Wiley & Sons, Inc.