Dimethyl phthalate ester degradation by two planktonic and immobilized bacterial consortia

Degradation of the plasticizer ortho-dimethyl phthalate ester (DMPE) was investigated using two reconstituted consortia under aerobic conditions. The consortia consisting of two and three bacterial cultures showed capability in the complete degradation of DMPE in less than 5 days at an initial concentration of 400 mg l−1. Consortium I, comprised of Pseudomonas fluorescens, P. aureofaciens and Sphingomonas paucimobilis, appeared to be more effective in degradation than Consortium II consisting of Xanthomonas maltophilia and S. paucimobilis. The Gompertz function and the Richards function were modified and used to fit the DMPE degradation data and the results indicated that the modified Richards model was always better than the modified Gompertz model in fitting the experimental data. In addition, microorganisms capable of degrading DMPE were subsequently immobilized on the microporous hollow fibres using calcium alginate entrapment techniques. The efficiency of DMPE degradation by the immobilized bacteria of Consortium I was compared with the batch culture system. The results showed that immobilization of microorganisms could further improve the rates of degradation. Our data suggest that microbial degradation of DMPE can be described by the modified Richards model and the plasticizer DMPE can be mineralized by consortia of bacteria either in planktonic culture or immobilized on surfaces.