產鹼假單孢菌A25分解鄰苯二甲酸二酯(DEHP)之研究及其胞外酯解酵素分析

Abstract

Phthalates, or phthalate esters, are esters of phthalic acid and are with characteristics of general low volatility and high stability, as a colorless viscous oily liquid, very low solubility in water. Phthalates are mainly used as plasticizers, substances added to plastics to increase their flexibility, transparency, durability and longevity. There is no covalent bond between the phthalates and plastics. So if the plastic by exposure to sunlight, high temperature heating or organic solvents, it has the opportunity to make the plasticizers released into the environment. Moreover, plastic aging will accelerate this process. The studies by EPA Taiwan found that DEHP is most abundant phthalate in Taiwan river sediment and fish body (Appendix. 2). In 2011 Taiwan plasticizer food safety incidents occur, unscrupulous industry use cheap DEHP as a food additive instead of a legal Cloudy agent added to food products. The study shows that the DEHP toxicity is more than melamine 3.5 to 20 times. DEHP is considered a potential carcinogen, environmental hormone and metabolic disruptors and is bound to seriously affect the health of the people. Thus, to solve environmental pollutants, DEHP becomes an important issue. Our study found that Pseudomonas alcaligenes A25 have the ability to degrade DEHP with good degradation efficiency. We analyze the degradation rate of DEHP by High performance liquid chromatography. At low concentrations (100 ppm) of DEHP about 24 hours to degrade 76% of DEHP, and at high concentrations (600 ppm) for about 48 hours to degrade 87% of DEHP. The strain A25 could degrade 98% DEHP within 192 hours. We found that strain A25 produce extracellular enzyme by DEHP induction. The extracellular enzyme after tributyrin agar medium and esterase activity staining tests confirmed having esterase activity. The optimal DEHP degradation conditions were 40℃ and pH 8.0. The addition of different nutrient sources and surfactants will affect degradation of DEHP. P. alcaligenes A25 as a newly discovered specie can efficiently degrade DEHP and produces extracellular esterase for DEHP degradation. It has the potential to degrade DEHP, perhaps can be applied to treatment of environmental pollutants DEHP.