Degradability of the three dimethyl phthalate isomer esters (DMPEs) by a Fusarium species isolated from mangrove sediment

Abstract

Dimethyl phthalate esters (DMPEs) are common plasticizersand additives to improve flexibility and softness of plastic products(Cartwright et al., 2000; Wang et al., 2004; Xu et al., 2005). ThreeDMPE-isomers, namely dimethyl phthalate (ortho-DMP; ortho-arrangement of the two carboxyl groups), dimethyl isophthalate(DMI; meta-) and dimethyl terephthalate (DMT; para-), display dif-ferent physical and chemical properties and are used in differentindustrial applications. DMP is used as a plasticizer in cellulose es-ter-based plastics (cellulose acetate and cellulose butyrate; Stapleset al., 1997). In polyester-based products, such as tape for VCR cas-settes, synthetic textile fibers etc., DMI and DMT are used as inter-mediates for their synthesis (Lee et al., 1999; Wang and Gu,2006a,b). Phthalate esters (PAEs) occur ubiquitously in both aqua-tic and terrestrial environments (Gu et al., 2005), and foods (Peter-sen and Breindahl, 2000). Because they do not bond covalentlywith the resin, leaching and migration of PAEs from plastic materi-als into the environment are of major concern for the potentialhealth problems associated with these chemicals. PAEs may actas endocrine disruptors affecting the normal function of the repro-ductive system and development of humans and animals at verylow concentrations (Jobling et al., 1995; Colon et al., 2000; Guet al., 2005; Xu et al., 2005). As a result, six PAEs including DMPare listed as priority pollutants by the United States EnvironmentalProtection Agency (Gu et al., 2005).It is suggested that complete degradation of PAEs in the envi-ronment is via microbial mineralization (Staples et al., 1997; Guet al., 2005). Degradation of PAEs has been well documented inbacteria. Various PAE-degrading bacteria have been isolated fromactivated sludge, mangroves, soils, rivers, and the marine environ-ment (Vegaand Bastide, 2003; Changet al., 2004; Gu et al., 2005; Liet al., 2005a,b; Xu et al., 2005; Wang and Gu 2006a,b; Fang et al.,2007). Both Gram-positive and Gram-negative bacteria are respon-sible for the aerobic degradation of phthalic acid (PA) via differentpathways (Chang and Zylstra, 1998; Stingley et al., 2004). Severalfunctional operons involved in the metabolism of PA have beenidentifiedand characterizedin Arthrobacter keyseri12B, Mycobacte-rium vanbaaleniiPYR-1, Burkholderia cepacia DBO1 and other bacte-rial strains (Chang and Zylstra, 1998; Eaton, 2001; Stingley et al.,2004). However, degradation of PAEs by fungi has rarely beenshown. Fungi have been demonstrated to be potential degradersof a wide range of recalcitrant compounds, including polycyclicaromatic hydrocarbons (PAHs), benzene–toluene–ethylbenzene–xylenes (BTEX), chlorophenols, polychlorinated biphenyl, muni-tions waste, and pesticides (Tortella et al., 2005). Nevertheless,degradation of PAEs by fungi has been studied only to a limited ex-tent with Aspergillus niger and Sclerotium rolfsii (Sivamurthy et al.,1991; Ganji et al., 1995; Pradeepkumar et al., 2000). The role offungi on the environmental fate of PAEs remains largely unknown.Coastal wetlands, such as mangroves, are usually sinks of pollu-tants from the aquatic system (Tam et al., 2001; Ke et al., 2005).Mangrove microorganisms may play an important role in the fateoforganicpollutantsinaquaticenvironments.Anumberofbacterialspecies capable of degrading PAEs have been isolated from man-grove sediments, such as Pseudomonas fluorescens, Rhodococcus ru-ber, Pasturella multocida, and Sphingomonas paucimobilis (Li et al.,2005a,b;Xuetal.,2005;LiandGu,2006).However,therearenore-ports concerned with the degradation of PAEs by mangrove fungi.The Futain Mangrove Nature Reserve of Shenzhen, China, is on thesouthern border of Shenzhen, one of the cities with the most rapideconomic development in China. The Reserve is under increasingpollution pressure derived from intense urbanization of the city,The objective of BASELINE is to publish short communications on different aspects of pollution of the marine environment. Only thosepapers which clearly identify the quality of the data will be considered for publication. Contributors to Baseline should refer to‘Baseline—The New Format and Content’ (Mar. Pollut. Bull. 42, 703–704).