Biodegradation of Dimethyl Phthalate by Freshwater Unicellular Cyanobacteria.

Xiaohui Zhang,Lincong Liu,Siping Zhang,Jing Li,Shiguo Xu,Yan Pan,Hongwei Pan,Feng Luo

doi:10.1155/2016/5178697

Xiaohui Zhang, Lincong Liu + Show 6 more

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https://doi.org/10.1155/2016/5178697

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Abstract

The biodegradation characteristics of dimethyl phthalate (DMP) by three freshwater unicellular organisms were investigated in this study. The findings revealed that all the organisms were capable of metabolizing DMP; among them, Cyanothece sp. PCC7822 achieved the highest degradation efficiency. Lower concentration of DMP supported the growth of the Cyanobacteria; however, with the increase of DMP concentration growth of Cyanobacteria was inhibited remarkably. Phthalic acid (PA) was detected to be an intermediate degradation product of DMP and accumulated in the culture solution. The optimal initial pH value for the degradation was detected to be 9.0, which mitigated the decrease of pH resulting from the production of PA. The optimum temperature for DMP degradation of the three species of organisms is 30°C. After 72 hours' incubation, no more than 11.8% of the residual of DMP aggregated in Cyanobacteria cells while majority of DMP remained in the medium. Moreover, esterase was induced by DMP and the activity kept increasing during the degradation process. This suggested that esterase could assist in the degradation of DMP.

Highlights

Phthalic acid esters (PAEs) are a class of refractory organic plasticizer compounds that are widely utilized as additives and plasticizers in a variety of polymeric products, including paints, cosmetics, and flexible plastics, such as plastic toys and containers [1,2,3]
Dimethyl phthalate (DMP) was introduced to BG11 medium at concentrations of 0, 20, 50, 200, and 500 mg L−1, and its effects on the growth of three Cyanobacteria were evaluated over 120 hours
Low concentration 20 mg L−1 DMP stimulated the growth of the three freshwater unicellular Cyanobacteria, but higher concentration could inhibited the growth

Summary

Introduction

Phthalic acid esters (PAEs) are a class of refractory organic plasticizer compounds that are widely utilized as additives and plasticizers in a variety of polymeric products, including paints, cosmetics, and flexible plastics, such as plastic toys and containers [1,2,3]. It has been well known that microorganism degradation is a vital process affecting the environmental fate of PAEs [20, 24] In addition to producing oxygen to meet the needs of heterotrophic bacteria and subsequently stimulate the activities of the bacteria degrading organic pollutants, Cyanobacteria and microalgae are capable of degrading organic pollutants directly, such as phenolics, polycyclic aromatic hydrocarbons, pesticides, petroleum, and PAEs [25] Most of those studies have focused on determining either optimizing conditions of PAEs or the degradation efficiency in some groups of organisms. Genome sequences and genetic manipulation techniques are insufficient for the Cyanobacteria used in the previous studies

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