Immobilization of Lipase in Polyacrylonitrile Nanofibers Prepared by Electrospinning for Production of Biodiesel
| Autor: | Shu Hong Xie, 謝樹泓 |
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| Rok vydání: | 2011 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 99 In this study, lipase was immobilized by absorption on electrospun polyacrylonitrile (PAN) nanofibers for production of biodiesel from soybean oil and methanol by transesterification. Experimental design was used to analyze the influence of five electrospinning variables on fiber diameters. Response surface methodology was used to obtain an equation predicting fiber diameters by multiple regressions. The optimum conditions for producing electrospun nanofibers were as follows: PAN solution concentration = 7.34 %, flow rate = 1.2 ml/hr, voltage = 19 kV, tip-to-collector distance = 8 cm, and temperature = 30 ℃. Nanofibrous membranes with 80 nm fiber diameter and 19.56 m2/g specific surface area could be obtained. Under the optimum immobilization condition using 30 mg/ml lipase solution, 52.49 U lipase activity could be immobilized on one gram of PAN membrane with lipase specific activity reaching 1.11 U/mg compared with free lipase at 0.0274 U/mg. The storage stability of immobilized lipase was improved compared with that of free lipase and the immobilized lipase still possessed 85.7% relative activity after 20 days in pH 7 phosphate buffer at room temperature. Two reaction systems were employed for the transesterification reaction, the excess methanol system and the equal molar methanol system. The effect of the amount of methanol, the amount of water, reaction temperature, and the amount of lipase used were studied for the excess methanol system. Under the optimum conditions, 3.908 g methanol, 3.108 g water, and 2.937 mg lipase could reacted with 13.3 g soybean oil to get 91.66 % conversion was obtained in 72 hr at 30℃. In equal molar methanol system, using 500 mg water and 2.088 mg lipase to react with 13.3 g soybean oil, 89.25 % conversion was obtained in 120 hr at 30℃. After six repeated batch reactions, the relative conversions of the two systems were 39.96 % and 51.73 %, respectively. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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