title: Effect of cell-surface hydrophobicity on bacterial conversion of water-immiscible chemicals in two-liquid-phase culture systems.
abstract: The effect of bacterial cell-surface hydrophobicity on the bioconversion of water-immiscible chemicals in an aqueous-organic (A/O) two-liquid-phase culture system was investigated. Escherichia coli JM109 and Rhodococcus opacus B-4 were used as hydrophilic and hydrophobic whole-cell catalysts, respectively. Hydroxylation reactions of monoaromatics, including toluene (log P(ow)=2.9), ethylbenzene (3.1), n-propylbenzene (3.4), and sec-butylbenzene (3.7), were employed as model conversions. When the todC1C2BA genes encoding Pseudomonas putida toluene dioxygenase were expressed in E. coli JM109, the yield of hydroxylated monoaromatics decreased with increasing substrate hydrophobicity. By contrast, R. opacus transformants, which expressed the todC1C2BA genes, showed high performance in the hydroxylation of monoaromatics, irrespective of substrate hydrophobicity. When the R. opacus transformants were examined for their ability to hydroxylate monoaromatics in an aqueous single-liquid-phase culture, the reaction velocity was markedly lower than that observed in the A/O two-liquid-phase culture. These results suggested that R. opacus B-4 accessed the hydrophobic substrates in the oil phase, thus making it more effective for the bioconversion reactions.
authors.affiliation: Department of Biotechnology, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan.
authors.forename: Takahiro
authors.initials: T
authors.lastname: Hamada
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Maeda
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Matsuda
authors.forename: Yuka
authors.initials: Y
authors.lastname: Sameshima
authors.forename: Kohsuke
authors.initials: K
authors.lastname: Honda
authors.forename: Takeshi
authors.initials: T
authors.lastname: Omasa
authors.forename: Junichi
authors.initials: J
authors.lastname: Kato
authors.forename: Hisao
authors.initials: H
authors.lastname: Ohtake
mesh_terms: D001673:Biodegradation, Environmental; D049308:Dioxygenases / Q000096:biosynthesis / Q000235:genetics; D004785:Environmental Pollutants / Q000378:metabolism*; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics / Q000254:growth & development*; D006841:Hydrocarbons, Aromatic / Q000378:metabolism*; D057927:Hydrophobic and Hydrophilic Interactions; D006900:Hydroxylation / Q000235:genetics; D044367:Phase Transition; D016958:Pseudomonas putida / Q000201:enzymology / Q000235:genetics; D012240:Rhodococcus / Q000201:enzymology / Q000235:genetics / Q000254:growth & development*
chemical_list: D004785:Environmental Pollutants; D006841:Hydrocarbons, Aromatic; D049308:Dioxygenases