Strain TIK-1 may be useful in the bioremediation of environments polluted by 4- tert-butylphenol and various other 4-alkylphenols. Along with the degradation of these alkylphenols, we detected methyl alkyl ketones that retained the structure of the original alkyl side chains. Degradation experiments with various alkylphenols showed that strain TIK-1 cells grown on 4- tert-butylphenol could degrade 4-alkylphenols with variously sized and branched side chains (ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, n-pentyl, tert-pentyl, n-hexyl, n-heptyl, n-octyl, tert-octyl, n-nonyl, and branched nonyl) via a meta-cleavage pathway but not 2- or 3-alkylphenols.
The rate of growth on 4- tert-butylphenol was much higher than that of growth on the other alkylphenols. Growth experiments with 20 other alkylphenols showed that 4-isopropylphenol, 4-sec-butylphenol, and 4- tert-pentylphenol, which have alkyl side chains of three to five carbon atoms with α-quaternary or α-tertiary carbons, supported cell growth but that 4-n-alkylphenols, 4- tert-octylphenol, technical nonylphenol, 2-alkylphenols, and 3-alkylphenols did not. We concluded that metabolism of 4- tert-butylphenol by strain TIK-1 is initiated by hydroxylation to 4- tert-butylcatechol, followed by a meta-cleavage pathway. When 3-fluorocatechol was used as an inactivator of meta-cleavage enzymes, strain TIK-1 could not degrade 4- tert-butylcatechol and 3,3-dimethyl-2-butanone was not detected. We identified 4- tert-butylcatechol and 3,3-dimethyl-2-butanone as internal metabolites by gas chromatography-mass spectrometry. The strain designated TIK-1 completely degraded 1.0 mM 4- tert-butylphenol in basal salts medium within 12 h, with concomitant cell growth. These strains are the first 4- tert-butylphenol-utilizing bacteria.
We isolated three Sphingobium fuliginis strains from Phragmites australis rhizosphere sediment that were capable of utilizing 4- tert-butylphenol as a sole carbon and energy source. Toyama, Tadashi Momotani, Naonori Ogata, Yuka Miyamori, Yuji Inoue, Daisuke Sei, Kazunari Mori, Kazuhiro Kikuchi, Shintaro Ike, Michihiko Isolation and Characterization of 4- tert-Butylphenol-Utilizing Sphingobium fuliginis Strains from Phragmites australis Rhizosphere Sedimentâ–¿ â€