碩士 / 淡江大學 / 化學工程與材料工程學系碩士班 / 100 / Yeast cells are immobilized on the calcium alginate beads in this study. The alginate beads are prepared using different calcium concentrations, and their filtration characteristics, such as the retardation time for compression and softness index, are measured by a dead-end filtration system. The filter medium used in experiments include mixed cellulose acetate (MCE) membranes with mean pore sizes of 0.025 μm and 0.1 μm, and Whatman #2 filter paper. The effects of suspension materials, filtration pressure, and calcium concentration on the filtration rate, filtration resistance, and cake filtration and compression properties are discussed.
In the filtration of pure sodium alginate, the serious fouling on the membrane surface results in highly compressible cake with extremely high resistance as well as a rapid decline in filtration rate. The filtration rate increases with increasing filtration pressure. When a yeast fermentation broth is filtered, the filtration rate declines slowly at the beginning because the main source of filtration resistances is the filter cake formed by yeast cells. The filtration resistance increases quickly after a period of filtration due to the cake compression. The cake formed by yeast behaviors highly compressible. Therefore, the average specific cake filtration resistance increases significantly with increasing filtration pressure. In the filtration of calcium alginate beads, an increase in filtration pressure leads to a lower filtration rate due to severe cake and particle compressions, and leads to lighter cake mass due to the percolation of inter-particle water. The alginate beads prepared under high calcium concentration are more hardness, lower compressibility and lower specific cake filtration resistance. In the filtration of yeast immobilized beads, the filtration curves of dt/dv can be divided into three parts. The first part of filtration curve is a straight line and similar to those of incompressible particle. In the second part, the filtration resistance increases suddenly because of particle deformation and low cake porosity. Most solid compressive pressures are depleted in the cake formed in this period. The newly formed cake layer in the last part has a relatively loose structure. The increase in filtration resistance therefore becomes far smaller compared to the second part. Because the effective specific surface area of particles increases when the cake porosity decreases under high pressure, the cake compression and particle deformation occur simultaneously. The softness index of particles is measured as 1.5 for the yeast immobilized beads. The yeast activity for immobilized beads remains 75 % for a long period, which is much higher than those in free suspensions. Comparing the results of this study with those in previous literatures, the size of calcium alginate beads prepared by this study (ca 1 mm) are smaller and the yeast activity is higher than those in previous literatures.
| Identifer | oai:union.ndltd.org:TW/100TKU05063017 |
| Date | January 2012 |
| Creators | Ping-Yuan Su, 蘇炳元 |
| Contributors | Kuo-Jen Hwang, 黃國楨 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 100 |
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