| Summary: | 碩士 === 國立宜蘭大學 === 食品科學系碩士班 === 96 === Because bacterial cellulose (BC) provides a strong structural network and biocompatibility, this study compared in situ cultivation and immersion complex techniques for the preparation of BC/gelatin composites (BC/G) that were crosslinked with transglutaminase (ATBC/G/T), genipin (ATBC/G/G), or 1-Ethyl-3-(3-dimethyl aminopropyl) carbodiimide (ATBC/G/E), with an aim of improving the mechanical strength and hydrophilic property of BC. When preparing BC/G via in situ fermentation, increased gelatin concentrations inhibited bacterial cell proliferation and decreased the carbohydrate utilization rate. The pH and soluble solid residual ratio were leveled off when ATBC was complexed with semi-solid gelatin. Furthermore, mechanical properties such as the storage moduli decreased. Alternatively, the BC/G composites prepared by the immersion technique displayed increased gelatin content, moduli and hardness as increased concentrations of gelatin were used in the immersion solution. EDC most effectively improved the mechanical properties of the ATBC/G composites; the G’ value of the ATBC/G/E composites was > 7 kPa, which was a 2－3 fold increase compared to the ATBC/G composites alone. Furthermore, the hardness value was approximately 5 kg. Scanning electron microscopy (SEM) analysis revealed that gelatin enters ATBC network, fills the empty spaces, and connects to the 3D structure of ATBC, covering it fully. The ATBC/G/G and ATBC/G/E composites maintain a network structure under 10% gelatin concentrations using the immersion technique because gelatin tightly attaches to the BC surface. The X-ray diffraction intensity of BC after alkaline treatment (ATBC) increases significantly, while the crystallinity increases from 33.33 to 75.88% after treatment. Though ATBC forms a composite with gelatin that does not change the crystal morphology of the cellulose, increased gelatin concentrations in addition to the crosslinking treatment decreased the degree of crystallization of the composite. The crystallinity of the ATBC/G/E composites was the most greatly reduced (41.19%). Fourier transform infrared spectroscopy (FTIR) of the ATBC/G composites revealed an absorption peak of 3200－3600 cm-1, indicating a trend elongating and demonstrating that the OH groups of the composites tends to increase. Therefore, after gelatin crosslinking, the crystallization formed from the hydrogen bonds between cellulose molecules is disrupted. Crosslinking can also decrease the syneresis of the composites, while enhancing the rehydration ratio. Overall, the immersion complex technique resulted in the elevated production of composites with enhanced mechanical properties as compared to the in situ fermentation technique. Increasing gelatin concentrations in the immersion technique will enhance formation of double network structures based on gelatin, thereby improving the mechanical strength and hydrophilic property of BC. Finally, the EDC-containing composites enhanced these physical properties to the greatest degree.
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