Delftia tsuruhatensis sp. nov., a terephthalateassimilating bacterium isolated from activated sludge Terephthalate is an aromatic compound used in the production of polyethylene terephthalate (PET) and is one of the top 50 most abundantly manufactured chemicals in the world (Savostianoff, 1990). A large amount of terephthalate is discharged during production of PET bottles and purification of terephthalic acid. Biological degradation of this compound has therefore been of interest in recent years.Several micro-organisms have been shown to degrade terephthalate under aerobic conditions, including the Gram-positive bacteria Nocardia sp. strain DSM 43251 (Engelhardt et al., 1979), a Bacillus species (Karegoudar & Pujar, 1985) and Dietzia sp. strain GS-1 (Sugimori et al., 2000). Among the Proteobacteria, Bordetella sp. strain K1, Pseudomonas sp. strain C4S (Kimura & Ito, 2001) and two Comamonas testosteroni strains, T-2 (Schläfli et al., 1994) and YZW-D (Wang et al., 1995), have demonstrated the ability to degrade terephthalate.Most of these micro-organisms have been reported to produce protocatechuate as an intermediate metabolite.The enzymic system responsible for the degradation of terephthalate has been thoroughly studied for C. testosteroni strain T-2. In that strain, terephthalate is degraded to protocatechuate by the terephthalate 1,2-dioxygenase system (TERDOS) (Schläfli et al., 1994) and protocatechuate is then metabolized via the meta cleavage pathway. Another C. testosteroni strain, YZW-D, reportedly uses a similar enzyme system for degradation of terephthalate (Wang et al., 1995).Recently, a novel terephthalate-assimilating bacterium, designated strain T7 T , was isolated from the activated sludge of a domestic wastewater treatment plant. The isolate could utilize terephthalate as sole carbon and energy source. Based on 16S rRNA gene sequences and phylogenetic analyses, strain T7T was placed in the genus Delftia;Abbreviations: MLSS, mixed liquor suspended solids; PET, polyethylene terephthalate; TERDOS, terephthalate 1,2-dioxygenase system; TOC, total organic carbon.
The terephthalate 1,2-dioxygenase system (TERDOS) was found in cell extracts of Delftia tsuruhatensis strain T7 ( = IFO16741) grown in terephthalate-salt medium. The cell extract was separated by anion exchange chromatography to yield two fractions (R and Z) that were necessary for oxygenation of terephthalate with NADH and Fe 2þ . The oxygenase component of TERDOS (TerZ) was purified from fraction Z by gel filtration chromatography to near homogeneity. An K 3 L 3 subunit structure was deduced from the molecular masses of 235, 46 and 17 kDa of the native complex and the K-and L-subunits, respectively. The N-terminal amino acid sequences of the two subunits of TerZ allowed polymerase chain reaction primers to be deduced and the DNA sequence of the K-subunit was determined. The amino acid sequence of the K-subunit (TerZK) showed significant similarities to the large subunits of multicomponent ring-hydroxylating oxygenases. Two motifs in the deduced amino acid sequence, a Rieske [2Fe^2S] center and a mononuclear Fe(II) binding site, were observed. Phylogenetic analyses indicated that TerZK and the large oxygenase component subunits ortho-halobenzoate 1,2-dioxygenase and salicylate-5-hydroxylase form a cluster that is distant from the rest of the large oxygenase subunits of multicomponent ringhydroxylating oxygenases. ß
Water-soluble pigment mixture was extracted from discolored nori seaweed without separating phycoerythrin (PE) and phycocyanin (PC). The stability of this mixture against light irradiation was studied for application as a violet food coloring additive. The PC component showed greater photo-stability than the PE component of the pigment solution (pH 7.0, 20℃) under irradiation at 5,300 and 7,800 Lx. The ratio of the second-order rate constant k PE /k PC which reflects photo-destruction was 9.3 (5,300 Lx) and 7.0 (7,800 Lx). The results were similar to those of a respective pigment separated by gel-chromatography. As for tonal changes, the a* value was decreased and both the b* and L* values were increased with progressing photo-destruction, namely, the violet color changed to pale dark-violet due to de-coloration of the red PE component. A reduction in photo-fading of 6.6% (PE) and 6.9% (PC) was achieved by 7,800 Lx irradiation for 5 h, compared with the control, by adding γ-cyclodextrin to the mixture.
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