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Study on Characteristics of the Nonylphenol-Degrading Enzyme

Author: ZhangMeiZhen
Tutor: ZhangXiaoFan
School: Shanghai Jiaotong University
Course: Environmental Engineering
Keywords: NP-degrading enzyme optimum conditions enzyme nature immobilization
CLC: X172
Type: Master's thesis
Year: 2012
Downloads: 79
Quote: 1
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Abstract


With the increasing demand of nonylphenol ethoxylates （NPEOs） used as surfactant, nonylphenol which is the NPEOs’main degrading product is also accumulating in the environment. As an estrogen-similar endocrine disruptor, NP has posed a potential threat to both the human health and the ecological security. So how to eliminate NP is becoming the hot spot both in and abroad in recent years.Many scholars have isolated strains from nature that can degrade NP, and have also made certain discussion on its degrading mechanism. Otherwise, reports on the NP-degrading enzyme is very few. In the paper, conditions of producing NP-degradation enzyme are optimized by using the strains named Serratia sp.LJ. Based on the optimum conditions, the enzyme property and immobilization is researched also.（1） Enzyme-producing conditions of NP-degrading strains named Serratia sp.LJ are optimized by the single factor and orthogonal experiments, then the result shows that, the enzyme production can be the highest after 72 hours under such conditions: taking NP as the only carbon source, the ammonium sulfate as nitrogen source, and the initial pH is 6.8, culture temperature is 30℃, the strain age is 24 hours, inoculums is 3%. That is 1.77 times of the enzyme production before optimization.（2） Under the optimum conditions, culture the strain for 72 hours and then stave cells in sonication. Extract NP-degrading enzyme through acetone、ethyl alcohol and ammonium sulfate, which can precipitate protein. The enzyme activity of the three parts indicate that finally volume fraction of acetone is 70% or ethyl alcohol is 75%, or saturation of ammonium sulfate is 75% could create the highest enzyme activity separately. In comparison, using acetone is better than the other two methods.（3） Enzyme nature has been analyzed after extracting the NP-degradation enzyme with acetone. Its most suitable pH is 6.5, and the most suitable reaction temperature is 35℃; controlling pH between 6.0 to 8.0 and the temperature between 30℃to 50℃can make the enzyme maintain higher stability; Cu2+、Zn2+、Ai3+ and Fe3+ can suppress enzyme catalytic reaction, K+ and Co2+ make no obvious change, Mn2+ and Ca2+ slightly increase enzyme activity, and the activation function of Mg2+ is most obvious.（4） Make the study of immobilized NP-degradation enzyme by sodium alginate. The experiment data shows that to bring the higher activity of the immobilized enzyme, the best dosage of sodium alginate is 3%, and CaCl2 is 2%, then recycling activity is 47%; the most suitable reaction temperature of immobilized enzyme is 35℃, and the most suitable pH is 7.0; its thermal stability, pH stability, operation stability and storing stability enhanced in varied degree.The research has made preliminary exploration of the NP-degrading enzyme’s physics and chemistry nature, thus could lay the foundation for the purification, chemical modification, the gene regulation of the NP-degrading enzyme, as well as creating the genetic engineering strain that can produce massive enzyme. Also, the paper could provide technical support to prepare enzyme on industry. In a word, the study has positive significance both to the environment and the science.

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