نوع مقاله : مقاله پژوهشی
نویسندگان
1 گروه بیوتکنولوژی صنعت و محیط، پژوهشکده علوم پایه کاربردی جهاد دانشگاهی، دانشگاه شهید بهشتی، تهران، ایران
2 گروه زمین شناسی محیطی، پژوهشکده علوم پایه کاربردی جهاد دانشگاهی دانشگاه شهید بهشتی، تهران، ایران
چکیده
کلیدواژهها
عنوان مقاله [English]
نویسندگان [English]
Introduction: Oil, as the most important economic resource in the country, not only generates income but also inevitably causes environmental pollution during the stages of extraction, refining, distribution, and storage. Microorganisms utilize degrading enzymes of petroleum compounds to break down hydrocarbons as a carbon source in environmental stress. Enzymes usage, due to their lack of pollution and controllability, is the best method for cleaning up environmental pollutants. One of the best enzymes for degrading oil compounds is ligninolytic enzymes produced by fungi. The aim of this study is to optimize the production of enzymes that degrade petroleum compounds for oil pollution cleanup.
Material and Methods: In this study, the fungal strain 2E, which was preserved in the microorganism bank of Academic Center for Education, Culture and Research (ACECR) of Shahid Beheshti University, was utilized, and its ability to produce ligninolytic enzymes was investigated. The experimental design was carried out with the Minitab 22.2.1 software for optimizing enzyme production, and the environment that had the highest protein level was identified using spectrophotometry and Bradford method. Enzymatic assays were performed at wavelengths of 420 and 595 nanometers for laccase and peroxidases, respectively, using suitable substrates. The concentration of protein in each of the specified environments was determined, and the degradation of crude oil was measured using lignin-degrading enzymes.
Results and discussion: Fungus was identified as a producer of ligninolytic enzymes. Decomposition of guaiacol and the color change of the culture medium to brown indicated the activity of the laccase enzyme and the reaction on substrate was confirmed by formation of red color in the presence of manganese peroxidase and decolorization of azure in the presence of lignin peroxidase. Using Minitab 22.2.1 software and cultivation results in 12 culture media from the experimental design with the aforementioned software, the stirring and inducing factors showed the greatest effect. The highest protein concentration was obtained under conditions of 5 grams per liter of glucose, 0.02 grams per liter of ammonium sulfate, 0.1 millimolar of copper sulfate, 4% crude oil, pH 7, temperature at 30 degrees Celsius, 15 milliliters of inoculum, and a stirring speed of 150 rpm. Three media with high protein concentration were tested for enzyme activity, and a direct relationship between protein concentration and the activity of ligninolytic enzymes was observed, leading to the selection of the optimal environment. The supernatant obtained from the fungal culture in the optimal condition was concentrated using ammonium sulfate precipitation and chromatography, with enzyme activity measured at 128.32 U/ml for laccase and 59.4 U/ml for peroxidases. The enzymatic biodegradation ability in the presence of crude oil was investigated, and based on the results of gas chromatography, the degradation rate of crude oil was calculated to be 88.3± 2.17 percent, which indicates a high degradation capability compared to other scientific reports regarding petroleum compounds. Ligninolytic enzymes, due to their wide substrate range and high structural flexibility, can react with petroleum compounds as pseudo-substrates and can lead to biodegradation and environmental cleanup.
Conclusion: Based on the results of this research, ligninolytic enzymes can be considered a powerful option for petroleum compounds biodegradation as a pseudo-substrate. From an economic perspective, optimizing ligninolytic enzymes production in an appropriate environment for practical use is important. It is hoped that the use of hydrocarbon-degrading enzymes as an environmentally friendly method will pave a new path for addressing oil pollution.
کلیدواژهها [English]
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