Method for measuring substrate preferences by individual members of microbial consortia proposed for bioaugmentation

In this study we used the assimilation of isotope labeled CO2 to measure the substrate preferences by two different bioaugmentation mixtures proposed for bioremediation of diesel oil contamination. All active microorganisms assimilate CO2 in various carboxylation processes involved in growth. The CO2 assimilation by the two mixtures was measured upon addition of glucose, diesel oil or specific compounds present in diesel oil (naphthalene, toluene, hexadecane, and octane). It was shown that within short term incubations with diesel oil (< 5 h), one bioaugmentation mixture was superior to the other regarding the assimilation of CO2. This observation was confirmed in a labor-intensive long term microcosm study (60 days). The applied method open various possibilities for fast pre-testing of substrate-preferences by microbial-bioaugmentation mixtures without microcosm experiments, onsite tests, and complicated chemical analysis. This study also demonstrates the possibility to obtain further information on the substrate preferences at a single cell level of phylogenetically defined microbial subgroups in bioaugmentation mixtures, based on combined analyses of microautoradiography and fluorescence in situ hybridization.