USE OF C-13 NUCLEAR-MAGNETIC-RESONANCE TO ASSESS FOSSIL-FUEL BIODEGRADATION - FATE OF [1-C-13]ACENAPHTHENE IN CREOSOTE POLYCYCLIC AROMATIC COMPOUND MIXTURES DEGRADED BY BACTERIA

[1-C-13]acenaphthene, a tracer compound with a nuclear magnetic resona nce (NMR)-active nucleus at the C-1 position, has been employed in con junction with a standard broad-band-decoupled C-13-NMR spectroscopy te chnique to study the biodegradation of acenaphthene by various bacteri al cultures degrading aromatic hydrocarbons of creosote, Site-specific labeling at the benzylic position of acenaphthene allows C-13-NMR det ection of chemical changes due to initial oxidations catalyzed by bact erial enzymes of aromatic hydrocarbon catabolism. Biodegradation of [1 -C-13]acenaphthene in the presence of naphthalene or creosote polycycl ic aromatic compounds (PACs) was examined with an undefined mixed bact erial culture (established by enrichment on creosote PACs) and with is olates of individual naphthalene-and phenanthrene-degrading strains fr om this culture, From C-13-NMR spectra of extractable materials obtain ed in time course biodegradation experiments under optimized condition s, a number of signals were assigned to accumulated products such as 1 -acenaphthenol, 1-acenaphthenone, acenaphthene-1,2-diol and naphthalen e 1,8-dicarboxylic acid, formed by benzylic oxidation of acenaphthene and subsequent reactions, Limited degradation of acenaphthene could be attributed to its oxidation by naphthalene 1,2-dioxygenase or related dioxygenases, indicative of certain limitations of the undefined mixe d culture with respect to acenaphthene catabolism. Coinoculation of th e mixed culture with cells of acenaphthene-grown strain Pseudomonas sp , strain A2279 mitigated the accumulation of partial transformation pr oducts and resulted in more complete degradation of acenaphthene, This study demonstrates the value of the stable isotope labeling approach and its ability to reveal incomplete mineralization even when as littl e as 2 to 3% of the substrate is incompletely oxidized, yielding produ cts of partial transformation, The approach outlined may prove useful in assessing bioremediation performance.