Comparative degradation by micro-organisms of terephthalic acid, 2,6-naphthalene dicarboxylic acid, their esters and polyesters C. LefeÁvre a , C. Mathieu a , A. Tidjani a,1 , I. Dupret a , C. Vander Wauven b , W. De Winter c , C. David a, * a Universite  Libre de Bruxelles, Chimie des Polyme Áres et des Syste Ámes organise Âs, Campus Plaine, Boulevard du Triomphe CP 206/1, 1050 Bruxelles, Belgium b Institut de Recherches du CERIA, Laboratoire de microbiologie, Avenue Emile Gryson1, 1070 Bruxelles, Belgium c Agfa-Gevaert N.V., R&D Laboratories, 2640 Mortsel, Belgium Received 3 July 1998; accepted 14 September 1998 Abstract Various derivatives of terephthalic acid (TA) and 2,6-naphthalene dicarboxylic acid (NDA) have been degraded in the presence of various strains of micro-organisms. These compounds include the dimethylesters (TME and NDME), the ethylene glycoldiesters (TGE and NDGE) and the corresponding ethylene glycol polyesters (PET and PEN). The terephthalic acid derivatives were shown not to be degraded by a pure strain of nonsporulating gram-positive bacteria isolated from an industrial compost for household refuse although this micro-organism eciently mineralizes aliphatic polyesters. The naphthalene dicarboxylic acid and derivatives did not allow growth of various Pseudomonas strains which assimilate naphthalene and some of its simple derived compounds. Therefore, isolation of micro-organisms degrading these aromatic acids and ester derivatives was performed using an enrichment technique. Garden soil or compost was used as sources of micro-organisms. Six strains eciently degrading TA, TME and TGE were isolated while only two strains assimilating NDA and NDME slowly, ineciently and with a bad reproductibility were obtained. PET and PEN were degraded by none of these strains. # 1999 Elsevier Science Ltd. All rights reserved. Keywords: Biodegradation; Terephthalic acid; 2,6-naphthalene dicarboxylic acid; Dimethylterephthalate; 2,6-naphthalene dimethylcarboxylate 1. Introduction Polyethylene terephthalate (PET) is a widely used polymer in the ®eld of packaging and may be, by con- sequence, at the origin of a waste problem although recycling techniques have been proposed. These seem to be well adapted to solve industrial waste problems but recovery and recycling of domestic waste still remains a challenge. Biodegradation oers an alternative possibi- lity to transform compostable waste into a fertilizer for agriculture. Therefore, industrial composting sites for household refuse are appearing all over Europe. Biode- gradation of PET has been widely studied [1,2]. Many publications claim that PET is not biodegradable even if some colonies of micro-organisms have been observed to grow on the polymer surface in some cases. Blends of PET with polycaprolactone [3] and copolymers obtained by transesteri®cation of the same polymers [4] have been tested in various biological environments. Variable degrees of biodegradability have been observed. Biodegradable copolyesters based on terephthalic acid have been reported recently [5,6]. A polyester derived from phthalic, isophthalic or terephthalic acid and poly(ethylene glycol) (PEG) is assimilated by symbiotic mixed cultures of a phthalate ester-hydrolyzing bacter- ium and a PEG-utilizing bacterium [5]. Weight loss is 100% after 8 weeks soil burial for the statistical copo- lymer poly(trimethylene-terephthalate-co-trimethylene- hexanedioate) containing 39 mol% of terephthalic acid in the acid fraction; melting temperature of this copoly- mer is 96  C [6]. Other aliphatic±aromatic copolyesters have been studied in the same work. Polyethylene 2,6-naphthalene dicarboxylate (PEN) is another aromatic polymer where 2,6-naphthalene dicarboxylic acid replaces terephthalic acid in PET. It is developing rapidly and holds promises for future devel- opments in the photographic and ®ber industries. Its Polymer Degradation and Stability 64 (1999) 9±16 0141-3910/99/$ - see front matter # 1999 Elsevier Science Ltd. All rights reserved. PII: S0141-3910(98)00164-5 * Corresponding author. Tel.: 0032 2 650 5406; fax: 0032 2 650 5402; e-mail: cdavid@ulb.ac.be 1 On leave from Universite Cheikh Anta Diop de Dakar, Faculte des Sciences, DeÂpartement de Physique, Laboratoire des D.S.T.N., Dakar-Fann, Se ne gal.