The metabolism of polyethylene glycol (PEG) was investigated with a synergistic, mixed culture of Flavobacterium and Pseudomonas species, which are individually unable to utilize PEGs. The PEG dehydrogenase linked with 2,6dichlorophenolindophenol was found in the particulate fraction of sonic extracts and catalyzed the formation of a 2,4-dinitrophenylhydrazine-positive compound, possibly an aldehyde. The enzyme has a wide substrate specificity towards PEGs: from diethylene glycol to PEG 20,000. Km values for tetraethylene glycol (TEG), PEG 400, and PEG 6,000 were 11, 1.7, and 15 mM, respectively. The metabolic products formed from TEG by intact cells were isolated and identified by combined gas chromatography-mass spectrometry as triethylene glycol and TEGmonocarboxylic acid plus small amounts of TEG-dicarboxylic acid, diethylene glycol, and ethylene glycol. From these enzymatic and analytical data, the following metabolic pathway was proposed for PEG: HO(CH2CH20)nCH2CH20H-+ HO(CH2CH20)nCH2CHO-* HO(CH2CH20)nCH2COOH-HO(CH2CH2-O),-0CH2CH20H.

Two different mixed cultures, which degrade terephthalate at 50 degrees C and pH 8, were isolated from a wastewater treatment plant. These were useful for the treatment of wastewater containing a high concentration of terephthalic acid (TPA). Each mixed culture included a TPA-degrading bacterium, strain K1 or Pseudomonas sp. C4S, and another bacterium unable to degrade TPA, the as-yet unclassified strain K3 or Bacillus sp. C4B. In axenic culture, K1 and C4S showed poor growth even in a medium supplemented with yeast extract and tryptone. On the other hand, when co-cultured with the co-isolate from the mixed culture which is unable to degrade TPA, the growth was enhanced. Moreover, several bacterial strains in our stock culture collection showed the ability to improve the growth of both TPA-degrading bacteria. A mixed culture of strains K1 and K3 exhibited rapid growth and TPA degradation in a chemically defined medium, suggesting that the mixed culture system would be applicable to the treatment of wastewater containing TPA.

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