Microbial degradation of polyethers

Abstract. This paper summarizes studies on microbial degradation of polyethers. Polyethers are aerobically metabolized through common mechanisms (oxidation of terminal alcohol groups followed by terminal ether cleavage), well-characterized examples being found with polyethylene glycol (PEG). First the polymer is oxidized to carboxylated PEG by alcohol and aldehyde dehydrogenases and then the terminal ether bond is cleaved to yield the depolymerized PEG by one glycol unit. Most probably PEG is anaerobically metabolized through one step which is catalyzed by PEG acetaldehyde lyase, analogous to diol dehydratase. Whether aerobically or anaerobically, the free OH group is necessary for metabolization of PEG. PEG with a molecular weight of up to 20,000 was metabolized either in the periplasmic space (Pseudomonas stutzeri and sphingomonads) or in the cytoplasm (anaerobic bacteria), which suggests the transport of large PEG through the outer and inner membranes of Gram-negative bacterial cells. Membrane-bound PEG dehydrogenase (PEG-DH) with high activity towards PEG 6,000 and 20,000 was purified from PEG-utilizing sphingomonads. Sequencing of PEG-DH revealed that the enzyme belongs to the group of GMC flavoproteins, FAD being the cofactor for the enzyme. On the other hand, alcohol dehydrogenases purified from other bacteria that cannot grow on PEG oxidized PEG. Cytoplasmic NAD-dependent alcohol dehydrogenases with high specificity towards ether-alcohol compound, either crude or purified, showed appreciable activity towards PEG 400 or 600. Liver alcohol dehydrogenase (equine) also oxidized PEG homologs, which might cause fatal toxic syndrome in vivo by carboxylating PEG together with aldehyde dehydrogenase when PEG was absorbed. An ether bond-cleaving enzyme was detected in PEG-utilizing bacteria and purified as diglycolic acid (DGA) dehydrogenase from a PEG-utilizing consortium. The enzyme oxidized glycolic acid, glyoxylic acid, as well as PEG-carboxylic acid and DGA. Similarly, dehydrogenation on polypropylene glycol (PPG) and polytetramethylene glycol (PTMG) was suggested with cell-free extracts of PPG and PTMG-utilizing bacteria, respectively. PPG commercially available is atactic and includes many structural (primary and secondary alcohol groups) and optical (derived from pendant methyl groups on the carbon backbone) isomers. Whether PPG dehydrogenase (PPG-DH) has wide stereo- and enantioselective substrate specificity towards PPG isomers or not must await further purification. Preliminary research on PPG-DH revealed that the enzyme was inducibly formed by PPG in the periplasmic, membrane and cytoplasm fractions of a PPG-utilizing bacterium Stenotrophomonas maltophilia. This finding indicated the intracellular metabolism of PPG is the same as that of PEG. Besides metabolization of polyethers, a biological Fenton mechanism was proposed for degradation of PEG, which was caused by extracellular oxidants produced by a brown-rot fungus in the presence of a reductant and Fe3+, although the metabolism of fragmented PEG has not yet been well elucidated.

[1]  F. Moriya,et al.  Bacterial assimilation of polytetramethylene glycol , 1991 .

[2]  J. Tiedje,et al.  Metabolism of polyethylene glycol by two anaerobic bacteria, Desulfovibrio desulfuricans and a Bacteroides sp , 1986, Applied and environmental microbiology.

[3]  N. Russell,et al.  Bacterial scission of ether bonds. , 1996, Microbiological reviews.

[4]  S. de Vries,et al.  Characterization of the gene encoding quinohaemoprotein ethanol dehydrogenase of Comamonas testosteroni. , 1996, European journal of biochemistry.

[5]  D. Bruns,et al.  Oxidation of polyethylene glycols by alcohol dehydrogenase. , 1989, Biochemical pharmacology.

[6]  F. Kawai.  Sphingomonads involved in the biodegradation of xenobiotic polymers , 1999, Journal of Industrial Microbiology and Biotechnology.

[7]  B. Schink,et al.  Fermentative degradation of polyethylene glycol by a strictly anaerobic, gram-negative, nonsporeforming bacterium, Pelobacter venetianus sp. nov , 1983, Applied and environmental microbiology.

[8]  N. Obradors,et al.  Efficient biodegradation of high-molecular-weight polyethylene glycols by pure cultures of Pseudomonas stutzeri , 1991, Applied and environmental microbiology.

[9]  M. Mohammadi,et al.  Description of chlorophenol-degrading Pseudomonas sp. strains KF1T, KF3, and NKF1 as a new species of the genus Sphingomonas, Sphingomonas subarctica sp. nov. , 1996, International journal of systematic bacteriology.

[10]  M. Yasuda,et al.  Polyethylene glycol dehydrogenase activity of Rhodopseudomonas acidophila derives from a type I quinohaemoprotein alcohol dehydrogenase , 1996 .

[11]  K. Jensen,et al.  Biodegradative mechanism of the brown rot basidiomycete Gloeophyllum trabeum: evidence for an extracellular hydroquinone‐driven fenton reaction , 1999, FEBS letters.

[12]  N. Yasuoka,et al.  Crystallization and preliminary x-ray study of two crystal forms of Klebsiella oxytoca diol dehydratase-cyanocobalamin complex. , 1999, Acta crystallographica. Section D, Biological crystallography.

[13]  F. Kawai,et al.  Inducible or constitutive polyethylene glycol dehydrogenase involved in the aerobic metabolism of polyethylene glycol , 1989 .

[14]  N. Russell,et al.  Ether-bond scission in the biodegradation of alcohol ethoxylate nonionic surfactants by Pseudomonas sp. strain SC25A. , 1996, Microbiology.

[15]  A. Yokota,et al.  Taxonomic Study of Polyethylene Glycol-Utilizing Bacteria: Emended Description of the Genus Sphingomonas and New Descriptions of Sphingomonas macrogoltabidus sp. nov., Sphingomonas sanguis sp. nov. and Sphingomonas terrae sp. nov. , 1993 .

[16]  B. Schink,et al.  Enzymes Involved in Anaerobic Polyethylene Glycol Degradation by Pelobacter venetianus and Bacteroides Strain PG1 , 1992, Applied and environmental microbiology.

[17]  Y. Tani,et al.  Bacterial Degradation of Water-insoluble Polymer : Polypropylene Glycol : Micronbial Degradation of Synthetic Polymers(II) , 1977 .

[18]  B. Schink,et al.  Fermentation of polyethylene glycol via acetaldehyde in Pelobacter venetianus , 1986, Applied Microbiology and Biotechnology.

[19]  R. Benz,et al.  Identification of two porins in Pelobacter venetianus fermenting high-molecular-mass polyethylene glycols , 1991, Journal of bacteriology.

[20]  M. Sugimoto,et al.  The First Step in Polyethylene Glycol Degradation by Sphingomonads Proceeds via a Flavoprotein Alcohol Dehydrogenase Containing Flavin Adenine Dinucleotide , 2001, Journal of bacteriology.

[21]  K. Matsushita,et al.  Three distinct quinoprotein alcohol dehydrogenases are expressed when Pseudomonas putida is grown on different alcohols , 1995, Journal of bacteriology.

[22]  A. Jongejan,et al.  Homology model of the quinohaemoprotein alcohol dehydrogenase from Comamonas testosteroni. , 1998, Protein engineering.

[23]  W. Bao,et al.  Rapid polyether cleavage via extracellular one-electron oxidation by a brown-rot basidiomycete. , 1998, Proceedings of the National Academy of Sciences of the United States of America.

[24]  O. Adachi,et al.  [76] Alcohol dehydrogenase from acetic acid bacteria, membrane-bound , 1982 .

[25]  Barbara A. Pearce,et al.  Metabolism of Di(ethylene glycol) [2-(2′-Hydroxyethoxy)ethanol] and Other Short Poly(ethylene glycol)s by Gram-negative Bacteria , 1980 .

[26]  F. Kawai,et al.  Purification and characterization of constitutive polyethylene glycol (PEG) dehydrogenase of a PEG 4000-utilizing Flavobacterium sp. no. 203 , 1989 .

[27]  M. Takeuchi,et al.  Taxonomical position of newly isolated polyethylene glycol-utilizing bacteria , 1996 .

[28]  F. Kawai,et al.  Purification and Characterization of an Ether Bond-Cleaving Enzyme Involved in the Metabolism of Polyethylene Glycol , 1997 .

[29]  J. Andreesen,et al.  Degradation of tetrahydrofurfuryl alcohol by Ralstonia eutropha is initiated by an inducible pyrroloquinoline quinone-dependent alcohol dehydrogenase , 1997, Applied and environmental microbiology.

[30]  J. Haines,et al.  Microbial Degradation of Polyethylene Glycols , 1975, Applied microbiology.

[31]  W. Payne,et al.  Anaerobic growth of Alcaligenes faecalis var. denitrificans at the expense of ether glycols and nonionic detergents. , 1983, Biotechnology and bioengineering.

[32]  R. Edlich,et al.  Toxicity of topical polyethylene glycol. , 1982, Toxicology and applied pharmacology.

[33]  J. Pelmont,et al.  Oxidation of polyoxyethylene oligomers by an inducible enzyme from Pseudomonas P 400 , 1980 .

[34]  W. Payne,et al.  Bacterial utilization of ether glycols. , 1962, Applied microbiology.

[35]  J. Jongejan,et al.  Enantioselective Conversions of the Racemic C3-Alcohol Synthons, Glycidol (2, 3-Epoxy-1-propanol), and Solketal (2, 2-Dimethyl-4-(hydroxymethyl)-1, 3-dioxolane) by Quinohaemoprotein Alcohol Dehydrogenases and Bacteria Containing Such Enzymes , 1994 .

[36]  F. Kawai.  Existence of ether bond-cleaving enzyme in a polyethylene glycol-utilizing symbiotic mixed culture , 1985 .

[37]  S. de Vries,et al.  Quinohaemoprotein ethanol dehydrogenase from Comamonas testosteroni. Purification, characterization, and reconstitution of the apoenzyme with pyrroloquinoline quinone analogues. , 1995, European journal of biochemistry.

[38]  J. Tiedje,et al.  Degradation of ethylene glycol and polyethylene glycols by methanogenic consortia , 1983, Applied and environmental microbiology.

[39]  P. Janssen,et al.  Microbial degradation of natural and of new synthetic polymers. , 1992, FEMS microbiology reviews.

[40]  K. Matsushita,et al.  Identification of the Prosthetic Group and Further Characterization of a Novel Enzyme, Polyethylene Glycol Dehydrogenase , 1985 .

[41]  F. Kawai,et al.  Purification and characterization of a glycolic acid (GA) oxidase active toward diglycolic acid (DGA) produced by DGA-utilizing Rhodococcus sp. No. 432 , 1991 .

[42]  B. Schink,et al.  THE BIOCHEMISTRY OF DEGRADATION OF POLYETHERS , 1987 .

[43]  Y. Murooka,et al.  Enzymatic Degradation of Ether-Alcohol Compounds , 1981 .

[44]  D. P. Cox.  The biodegradation of polyethylene glycols. , 1978, Advances in applied microbiology.