Journal of Microbiology

Characterization of BTX-degrading bacteria and identification of substrate interactions during their degradation: Oh, Young Sook , Choi, Sung Chan; J. Microbiol. 1997;35(3):193-199.

Abstract: From several industrial wastewaters, 14 bacterial strains which degrade benzene, toluene, o-xylene, m-xylene, or p-xylene (BTX) were obtained. These strains were characterized as to their species composition and the substrate range, kinetic parameters and the substrate interactions were investigated. Although BTX components have a similar chemical structure, isolated strains showed different substrate ranges and kinetic parameters. None of the strains could degrade all of BTX components and most of them showed an inhibition (Haldane) kinetics on BTX, BTX mixtures were removed under inhibitory substrate interactions with variation in the intensity of inhibition. For a complete degradation of BTX, a defined mixed culture containing three different types of pathways was constructed and all of the BTX components were simultaneously degraded with the total removal rate of 225.69 mg/g biomass/h Judging from the results, the obtained mixed culture seems to be useful for the treatment of BTX-contaminated wastewater or groundwater as well as for the removal of BTX from the contaminated air stream.

Roles of the meta- and the ortho-Cleavage Pathways for the Efficient Utilization of Aromatic Hydrocarbons by Sphingomonas yanoikuyae B1: Jeongmin Song , Junghee Sung , Young Min Kim , Gerben J. Zylstra , Eungbin Kim; J. Microbiol. 2000;38(4):245-249.

Abstract: Catabolic pathways for the degradation of various aromatics by Sphingomonas yanoikuyae B1 are intertwined, joining at the level of substituted benzoates, which are further degraded via ring cleavage reactions. The mutant strain EK497, which was constructed by deleting a large DNA region containing most of the genes for biphenyl, naphthalene, m-xylene, and m-toluate degradation, was unable to grow on all of the aromatics tested except for benzoate as the sole source of carbon and energy. S. yanoikuyae EK497 was found to possess only catechol ortho-ring cleavage activity due to deletion of the genes for the meta-cleavage pathway. Wild-type S. yanoikuyae B1 grown on benzoate has both catechol ortho-and meta-cleavage activity. However, m-xylene and m-toluate, which are metabolized through methylbenzoate, and biphenyl, which is metabolized through benzoate, induce only the meta-cleavage pathway, suggesting the presence of a substrate-dependent induction mechanism.

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