The production of fungal chitosan by solid substrate fermentation | |
| Author | Ni Tar Nwe |
| Call Number | AIT Diss. no.BP-02-02 |
| Subject(s) | Chitin Chitosan Solid-state fermentation |
| Note | A dissertation submitted in partial fulfillment of the requirement for the degree of Doctor of Technical Science, |
| Publisher | Asian Institute of Technology |
| Series Statement | Dissertation ; no. BP-02-02 |
| Abstract | Fungal mycelia of Gongronella buttleri can be grown in solid substrate and submerged fermentation. Solid substrate fermentation was used in this research since the
design of the fermenter can be very simple and cheap and can be optimized easily for the large scale with low cost of operation.
In the fungal mycelia, chitosan is produced in 3 forms: as free chitosan, as free
precursor chitin and as chitosan/chitin covalently bound to glucan. Free chitosan has extracted, but the yield is very low about 2 g chitosan/100 g mycelia. Chitosan was derived from chitin aะer chemical deacetylation using concentrated alkali. It was found that chitosan (or chitin) bound to glucan can be easily freed by treatment with Termamyl, Type LS. Optimal conditions have been established for this process. Those are pH 4.5, 65°C, 200 rpm during 3 h. The sensitivity of the bond between chitosan and glucan suggest that chitosan may be linked to the glucan chain by on-1,4 glucosidic bonds. This chitosan extraction method can be used for the industrial scale production of fungal chitosan. In the solid substrate fermentation, the fungal mycelia were grown on sweet potato pieces for 7 days. Only 0.69 g chitosan/kg of sweet potato could be extracted from the fungal
mycelia. The chitosan yield was increased to 1.54 g chitosan per kg of sweet potato (w.b)
supplied with mineral solution. Production was further optimized by supplementing various nitrogen sources to the solid substrate fermentation media. It was observed that urea is the best N source for fungal chitosan production. However, high amounts of urea result in a high
pH of the fermentation medium. The chitosan production yield was increased to 3.60 g/kg of sweet potato supplemented with 7.2 g urea and adjusted to pH 4.5.
Lnoculum size was varied from 0.15 to 24 x 108 spores/kg sweet potato (w.b). The
yield of mycelia in various fermentations appeared to be independent of the inoculum size. Variation in the rate of the airflow did not result in variation of the production of mycelia and chitosan content. More mycelium, and more chitosan, 4.6 g/kg of sweet potato (w.b), was obtained after fermentation at 29°C. The yield of mycelia decreased with the decrease of moisture content of solid substrate. The fungus chitosan has a degree of deacetylation 87-90 % and a number average molecular weight of 20 - 70 kDa. These specifications meet the requirements for pharmaceutical application. The physio chemical progenies of chitosan were rather constant irrespective fermentation conditions. It is concluded that growth of Gongronella bulrleri in solid substrate fermentation on sweet potato pieces is an efficient method for the production of non-shrimp chitosan. Specific conditions are an inoculum size of 1.5 x 107 spores/kg sweet potato (wb), 1.2 l min"(l |
| Year | 2002 |
| Corresponding Series Added Entry | Asian Institute of Technology. Dissertation ; no. BP-02-02 |
| 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) | Suwanlee Chandrkrachang;Athtapol Noomhorm;Mousa M. Nazhad;Suwabun Chirachanchai;Durand, Alain; |
| Scholarship Donor(s) | Asian Institute of Technology; |
| Degree | Thesis (Ph.D.) - Asian Institute of Technology, 2002 |