Production of novel oligosaccharides by microbes and evaluation of their function

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1.Preparation of Raw Material for Oligosaccharides Production : Extraction and purification of inulin from chicory was attempted according to the method of sugar purification from beet, and was successfully achieved. Preparation of levan was also carried out by using levan producing bacteria, and levan was recovered and purified from its culture broth. More simple purification process for preparation of raw material has attempted by such method as addition of oligosaccharide-producing enzyme to crude extracts.2.Screening and Improvement of Oligosaccharide Producing Microbe : Oligosaccharide producing microbe was screened from plant in addition to soil as a screening source, and xylobiose-producing fungi was newly isolated. Molecular cloning of ift and lft gene, which encode DFAIII and DFAIV producing enzyme respectively, were executed. Expression systems of ift and lft gene was constructed in E.coli system, and higher activities were gained by using these system rather these original strains.3.Establishment of Oligosaccharide Production Process : Culture conditions for oligosaccharides producing enzymes and reaction conditions were optimized by characterizing microbes and enzymes producing DFAIII,DFAIV,inulotriose and levanbiose. Large scale preparations of purified DFAIII and DFAIV were gained by the process such as fermentation of reaction mixturi by yeast, ion exchange column and crystallization.4.Evaluation of Physiological Function of Oligosaccharide : Properties of DFAIII with respect to both industrial processing and nutritional function by using microbe, rat and human were examined. In the case of rat, calcium absorption was increased by adding DFAIII to feed, and the regions of absorption were determined in large and small intestines. Physiological fuction of DFAIV has also been evaluation.