| Summary: | 碩士 === 國立中興大學 === 食品暨應用生物科技學系所 === 104 === In recent years, many studies have reported using submerged fermentation to cultivate fungi and extract the polysaccharides. However, the extracted polysaccharide is limited in industrial application due to high molecular weight, low solubility, and difficulty in transport across cell membrane. Germany successfully synthesized carboxymethyl cellulose by carboxymethylation, which transformed insoluble cellulose into the water-soluble form. This technique of carboxymethylation can be applied to the chemical modification of polysaccharide. This chemical modification not only improves the physicochemical properties, but also obtains new functions to polysaccharide.
This study extracted exopolysaccharide from Tremella resupinata BCRC 36818, which has the highest exopolysaccharide production in four selected Taiwan native Tremella spp. After carboxymethylation of T. resupinata BCRC 36818 exopolysaccharide (T. resupinata BCRC 36818 exopolysaccharide, TRP), two different degrees of substitutions have been prepared in this study, including the low degree of substitution of carboxymethyl T. resupinata BCRC 36818 exopolysaccharide (CMTRP1, low degree = 0.491) and the high degree of substitution of carboxymethyl T. resupinata BCRC 36818 exopolysaccharide (CMTRP2, high degree = 1.077). The results indicated that the carboxymethylated exopolysaccharides not only improved solubility and water retention capacity but also decreased intrinsic viscosity. In addition, the carboxymethylated exopolysaccharide increased the moisture absorption and retention activity. From the results of antioxidation, CMTRP2 showed the significant chelating effect on ferrous ion. The results of cytotoxicity test indicated that all samples (TRP, CMTRP1 and CMTRP2) have more than 77% of cell viability when co-incubated with Raw 264.7 for 24 hours, which showed that samples were non-cytotoxic. When the samples were co-incubated for 48 hours, lower cell viability (less than 60%) and higher NO production can be found at the high concentration of CMTRP2 (higher than 1,000 μg/mL).
When T. resupinata BCRC 36818 was cultivated in the bench-top bioreactor with Zhao scholar’s Tremella spp. medium (ZTM), which not only obtained higher exopolysaccharide production (5.34 g/L), but also lower the cost compared to PDB medium. The higher exopolysaccharide production and lower cost showed the potential for industrial application. The results of this study demonstrated that carboxymethylated exopolysaccharides are worth for further investigation.
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