| Summary: | 碩士 === 靜宜大學 === 食品營養研究所 === 95 === Abstract
Recently there have been great interests in prebiotic properties of fructooligosaccharides (FOS). Traditionally, FOS are produced by degradation of chicory inulins, but the composition, yield and molecular weight of the product were not easily controlled, in contrast to enzymatic synthesis. Therefore, this study was to investigate the production condition of new FOS using β–fructosyl transferase from Aureobasidium pullulans. The experiments were conducted for finding the optimal cultivate condition of A. pullulans and the effects of ethanol-water mixture as reaction media and removing glucose by glucose oxidase, and finally using the mixture of activated charcoal and Celite as adsorbants to purify the FOS products for microbial activity analysis. The results showed that the extracellular broth of A. pullulans after 96 h incubation exhibited 10.2 U β–fructosyl transferase activity (hydrolase activity 7 U, transferase activity 3.2 U). The 20% sucrose added with the broth for reaction at pH 5.5, 55oC and 150 rpm for 5 hr could yield the mixtures containing tri- to pentasaccharides. Adding xylose and ababinose as donors in 5-10% ethanol reaction systems resulted in various heterogeneous FOS, despite that elevating ethanol concentration did not significantly enhance the FOS yield. The incorporation of glucose oxidase could effectively remove glucose and increase FOS yield for the pure sucrose system. But, this was not for the case of the sucrose mixtures with xylose or arabinose. After adsorbing by activated charcoal-Celite mixture (1:2 w/w) and followed by eluting with 30% ethanol, the adsorbing rate of the FOS preparation was found up to 80%. Using the purified FOS as a carbon source, the total counts of Bifidobacterium longum and Propionibacterium freudenreichii were not significantly improved in either single culture or co-culture. However, the resultant fermentation broths of B. longum and P. freudenreichii possessed some antimicrobial activities for a certain species of pathogens such as Escherichia coli, Propionbacterium acnes, and Clostridium perfringens, but not for Salmonella typhimurium.
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