Enzyme immobilization on modified chitosan matrix | |
| Author | Rahman, Tawhidur |
| Call Number | AIT Thesis no.BT-03-19 |
| Subject(s) | Chitosan Enzymes Immobilized enzymes |
| Note | A thesis submitted in partial fulfillment of the requirement for the degree of Master of Science, School of Environment, Resources and Development |
| Publisher | Asian Institute of Technology |
| Series Statement | Thesis ; no. BT-03-19 |
| Abstract | Chitosan has shown to be a good matrix for enzyme immobilization because of its cationicity and biocompatibility. But the solubility of chitosan in acidic pH limits its use in many industrial applications. Therefore, chitosan (CTS) is commonly cross-linked with glutaraldehyde to get stable matrix for immobilization. The toxicity of glutaraldehyde hinders the use of prepared matrix in food, cosmetic and pharmaceutical applications. Recently, modified chitosans prepared in Bioprocess Technology Laboratory have shown to be stable in acidic pH with good adsorptibility and the modification procedure did not include any toxic compounds. In this study, these modified chitosan matrices were studied for the potential use of enzyme immobilization. Alternatively, interpenetrating polymer network (IPN) prepared from the ionic interaction between cationic and anionic polyelectrolytes are also shown to be stable in acidic pH. Therefore the stability of IPN beads prepared with chitosan and other anionic polyelectrolytes such as xanthan (XAN), alginate (ALG) and carrageenan (CAR). The increasing order of the stability of IPN beads in acidic pH at 50°C was found to be CAR>CTS-ALG>CTS-XAN. The use of 8-10% KCl to form carrageenan beads further causes the precipitation of chitosan from chitosan solution. As a consequence, the interaction between chitosan and carrageenan was inhibited. Throughout the study, the industrial starch enzyme Termamyl, Type LS (Novo) containing a-amylase was used for immobilization since the enzyme can work at high temperature but does not have any chitinolytic activity. Among the various beads tested, citrate crosslinked chitosan bead has shown highest immobilization efficiency without losing much of its initial enzyme activity even after 5 runs. Besides, the immobilized enzyme has also shown to possess same activity as free enzyme. The decrystallized chitosan powder has shown the same immobilization efficiency but the recovery of fine chitosan powder mixed with starch solution after the enzyme activity test was difficult in reuse. The entrapment of Termamyl in IPN was not successful. The CTS-XAN beads were soft and could not withstand at 50°C. Although CTS-ALG beads are stronger, the gradual swelling of the beads during incubation make difficult to immobilize the enzyme. The highest physical stability was found in carrageenan beads, but after the entrapment of enzyme, the beads became unstable. The incubation of Termamyl with carrageenan showed that the enzyme could degrade the carrageenan. Apparently, the other enzymes present in commercially prepared Termamyl were responsible for the action. |
| Year | 2003 |
| Corresponding Series Added Entry | Asian Institute of Technology. Thesis ; no. BT-03-19 |
| Type | Thesis |
| School | School of Environment, Resources, and Development (SERD) |
| Department | Department of Food, Agriculture and Natural Resources (Former title: Department of Food Agriculture, and BioResources (DFAB)) |
| Academic Program/FoS | Food Engineering and Bioprocess Technology (FB) |
| Chairperson(s) | Stevens, Willem F.; |
| Examination Committee(s) | Suwalee Chandrkrachang;Thammarat Koottatep; |
| Scholarship Donor(s) | The Royal Netherlands Government; |
| Degree | Thesis (M.Sc.) - Asian Institute of Technology, 2003 |