| Summary: | 碩士 === 國立成功大學 === 化學工程學系碩博士班 === 90 === In this study, chitosan is used as an immobilization matrix. Pseudomonas putida is entrapped by physical iontropic gelation with chitosan and the resulting beads are used as a biocatalyst for the biodegradation of phenol. Two important issues were investigated about these beads:
1. The surface and cross-section morphology of the beads: the structure of the beads formed by different iontropic gelation procedures were observed by scanning electron microscopy (SEM). To avoid bacteria leakage and attain an effective immobilization, the high surface porosity and small pore diameter that is less than 0.2μm are sought. In addition, the core of the beads shouldn’t be too dense, so as to provide enough growing space for bacteria.
2. The viable bacteria concentration inside the bead: the quantification of bacteria is difficult since the lysis for the chitosan bead was hard. Thus, the following experiments were performed. One is the concentration of the bacterial loss during entrapment. The other is the viable ratio of the bacteria after contact with the solution used for immobilization. Henceforth, the viable bacteria concentration entrapped inside the bead can be calculated.
Chitosan beads formed by using 2% chitosan solution gelation in 1% sodium tripolyphosphate solution is strong enough to bear the aeration and shaking tests. This indicates the stability of the chitosan beads were satisfactory. The surface pore diameter of the beads formed is ranging from 1 to 6 μm. This might result in the leakage of bacteria entrapped. High molecular weight and high degree of deacetylation of the chitosan can lead to a better bead formation in the gelation solution. In addition, the core of the beads will become denser with the increase of the chitosan concentration, and this will limit bacteria growth. Most of all, it was found that the bacteria is denatured after its contact with chitosan solution. This may be attributed to the antibacterial property associated with chitosan as well as the acidic environment of the chitosan solution.
|
|---|
