Journal of Microbiology

Formation of humus-bound residues in the course of BTX biodegradation in soil: Song , Hong Gyu; J. Microbiol. 1997;35(1):47-52.

Abstract: To examine whether the xylene component of BTX (benzene, toluene, xylene) mixture is cometabolized and residues are produced in soil, ¹⁴C-labeled-0-xylene was added to sandy loam in combination with unlabeled benzene and toluene. After 4 weeks of incubation in a sealed system connected to an oxygen reservoir, 55.1% of the radiocarbon was converted to ¹⁴CO₂, 3.0% was to 95.8% radiocarbon recovery. Biomass incorporation of o-xylene radiocarbon which was detected by fumigation/extraction was usually low (5.6%), but 32.1% radiocarbon became associated with soil humus. Most of the numus-bound radiocarbon was found in humin fraction. In addition to o-xylene, p-xylene and toluene also showed similar results. The evidence shows that some of their reactive methylcatechol biodegradation intermediates attach to the humic metrix in soil in preference to mineralization and biomass incorporation.

Biodegradation of aromatic hydrocarbons by several white-rot fungi: Song , Hong Gyu; J. Microbiol. 1997;35(1):66-71.

Abstract: To investigate the biodegrading capability of several white-rot fungi isolated in Korea, biodegradation of BTX (benzene, toluene, xylene), phenanthrene and pyrene were tested in fungal cultures. Phanerochaete chrysosporium removed 20-30% of BTX mixture during 21 days of incubation in serum bottle. Coriolus versicolor KR-11W and Irpex lacteus mineralized 10.02 and 8.26% of totla phenanthrene, respectively, which were higher than in other studies with P. chrysosporium. These two strains also showed high mineralization rates (9.2-10.1%) for 4-ring pyrene. I. lacteus metabolized most of the added pyrene and 23.29% was incorporate dinto fungal biomass. Almost 50% of the pyrene was converted to polar metabolites and recovered from aqueous phase of culture. These results indicated that some white- rot fungi have higher biodegradability than P. chrysosporium and could be used in bioremediation of aromatic hydrocarbon contaminants in soil.

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.

Degradation of Gaseous BTX by Biofiltration with Phanerochaete chrysosporium: Oh, Young Sook , Choi, Sung Chan , Kim, Yeong Kwan; J. Microbiol. 1998;36(1):34-38.

Abstract: Biodegradation of benzene, toluene, and o-, m-, p-xylenes(BTX) by the white rot fungus, Phanerochaete chrysosporium was studied in a biofilter. P. chrysosporium was cultured under shaking conditions on YMG growth medium and homogenized pre-grown cells were transferred to biofilter. A preliminary batch culture experiment showed that all BTX components were degraded simultaneously without any observable substrate interactions, while the rate constant was the highest for p-xylene and lowest for benzene. For the biofiltration of the BTX, the BTX compounds were individually vaporized from 3 glass bottles containing benzene, toluene, and xylenes, respectively, by applying air flow. The vaporized fluxes of the compounds were immediately taken by the air current to the biofilter through the horizontal tube at the rim of the source other than the pollutants themselves. The effect of air flow rate (0.026~0.450 l/h) on the degradation of the compounds was evaluated in the biofilter packed with glass beads. A substantially higher degradation of all the BTX compounds was observed at higher flow rates, suggesting that mass transfer is a limiting factor in the degradation process. At a flow rate of 0.026l/h, there was no substantial difference in the extent of degradation between the two support media.

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