| Summary: | 碩士 === 國立中興大學 === 食品安全研究所 === 107 === Chitosan is one of the most abundant natural resources found on the earth and is generally prepared by the deacetylation of chitin, found in the skeletal materials of crustaceans and insects, and the cell walls of bacteria and fungi. However, the commercial production of chitosan by shrimp and crab shells has seasonal restrictions, and fungi are easy to culture, regardless of seasonal and raw material sources. It also produces high yields of biomass. Therefore, fungal chitosan has become an attractive alternative source of production of chitosan.
In this study, chitosan was prepared by the biomass method. We chose the most suitable mold strain which recognized as safe fungi for preparing foods for the production of chitosan. The influences of fungi growth under different culture conditions on biomass, chitosan content and chitosan concentration were assessed, and determined their antimicrobial activity and chitosan film properties.
The results showed that the chitosan produced by Actinomucor taiwanensis BCRC 31159 had the highest chitosan concentration, and inoculated with 4% spore suspension in the optimal medium (PDB supplemented with 15 g/L peptone), which was cultured at condition of initial pH 5, 30 ° C and 200 rpm rotary shaker for 3 days. After drying and extraction, the amount of mycelium could be weighed to 10.36±0.21 g/L, chitosan content was 12.84±0.80% (w/w) and the chitosan concentration was 1.33±0.08 g/ L.
In addition, antibacterial studies showed that 0.5% chitosan-acetic acid solution could significantly inhibit the growth of Escherichia coli, the inhibition rate was 98%, and the lower concentration of chitosan could also effectively slow down the growth rate. After the fungal chitosan was made into a film, it has the characteristics of high tensile force (7.30±1.91 N/mm2), elongation at break (28.28±6.77%) and high water vapor permeability, which could be used as a material for fruits and vegetables.
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