Improved production of shrimp chitin and chitosan using physico-chemical and biocatalytical treatments | |
| Author | Kyaw Nyein Aye |
| Call Number | AIT Diss. no.BP-03-03 |
| Subject(s) | Enzymes Chitin Chitosan Enzymes in animal nutrition |
| Note | A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy |
| Publisher | Asian Institute of Technology |
| Abstract | Chitin and chitosan from shellfish is a natural cationic and physiotopically active biopolymer, that is recovering more and more by the large range of applications in aquaculture, industry and environmental management. The standard procedure of chitin and chitosan production has been optimized and applied on pilot scale using 100-kg batches of biowaste of black tiger shrimp (Penaeus monodon). The extraction of chitin, carried out at room temperature (30 °C) has two advantages: less damage to the product and less corrosion of the equipment. The yield of chitin in dried form is 6 to 7 % of wet raw material. Deacetylation was carried out using 50 % sodium hydroxide to obtain chitosan. A single deacetylation gave 60 to 70 % degree of deacetylation whereas double deacetylation resulted in 90 % degree of deacetylation. Chitosan yield was about 5 % (dry weight of chitosan / wet weight of original waste). The production of superfine chitin, by dissolution of dry chitin in methanol, saturated with CaCl22H2O followed by controlled precipitation by additional methanol, has been improved and scaled up. By various pretreatments of the biowaste, partial deproteination could be achieved. Physical pretreatment of dry waste comprising of drying, grinding and sieving is attractive for the recovery of a dry powder rich in shrimp protein. Pretreatment of wet waste by shearing in acidified water results in the removal of 50 % of the protein without a decrease in the chitin yield. This pretreatment also reduces the calcium content of the shells, and as a result, the amount of chemicals required in the further decalcification and deproteination processes can be reduced by 60 %. Both dry and wet waste pretreatment procedures lead to cleaner technology for chitin production, to considerably lower costs, to useful by-products and to less contaminated industrial effluent. Chitin and chitosan production can be facilitated by biocatalytic treatment in various ways. Protease enzyme was used to promote the release of protein from wet biowaste. The enzyme chitin deacetylase can be used to deacetylate chitin in a very controlled and specific way to enhance the adsorptive power of chitosan. To make the enzymatic deacetylation more practical, the CDA enzyme from the fungi Absidia coerulea, Colletotrichum lindemuthianum and Rhizopus oryzae were checked for their specific enzyme activity on various chitin substrates, i.e , partially deacetylated chitin and superfine chitin. The CDA from A. coerulea has a high activity with partially deacetylated chitin (PDC) as substrate but the enzyme cannot act on natural chitin and superfine chitin. The CDA from C. lindemuthianum is active on natural chitin and PDC. But, both enzymes could only deacetylate a minor fraction of the total amount of acetyl groups present in the sample during l - 2 hours incubation. The specific CDA activity was increased when soybean residue was added as growth medium for the fungi. It was observed in that case that the specific enzyme activity of CDA from R. oryzae tested with superfine chitin as substrate is twice that of CDA from A. coerulea with PDC as substrate. It is concluded that the Rhizopus enzyme has the highest potency for the enzymatic deacetylation. As a working hypothesis, it is proposed that the enhanced absorptive power of chitin powder by treatment with CDA is due to the formation of chitin particles in which the interior remains unchanged and insoluble in acid, whereas the acetyl groups at the exterior of the chitin particle are removed. The surface of chitin acquires the property of that of a chitosan particle. In this way, insoluble but very absorptive chitin particles can be obtained. The CDA treated chitin that is superb in protein chromatography has also shown very effective in the binding of dye and pigment as well as in the clarification of wastewater from a textile dye factory. |
| Year | 2003 |
| Type | Dissertation |
| 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 | Bioprocess Technology (BP) |
| Chairperson(s) | Stevens, Willem F.; |
| Examination Committee(s) | Suwalee Chandrkrachang;Nazhad, Mousa M.;Yakupitiyage, Amararatne;Udomchai Chinadit;Hudson, Samuel M.; |
| Scholarship Donor(s) | Asian Institute of Technology Fellowship; |
| Degree | Thesis (Ph.D.) - Asian Institute of Technology, 2003 |