Production of useful oligosaccharides from unused polysaccharides by microbial enzymes

寡糖具有抗龋齿、预防便秘、降低血浆胆固醇、低热量甜味剂等生理功能，是植物和微生物的优良保健物质，近年来受到人们的广泛关注。随着低聚物的重要性被认识到，显然其生产方法的开发变得重要。因此，我们开始研究使用廉价的起始材料如菊粉和莱万通过微生物方法生产低聚果糖。从土壤样品中分离出多种降解菊粉或莱万的微生物，并筛选出低聚糖产生菌.从菊糖生产低聚糖：产生二果糖酐III（DFA III）的节杆菌H65 -7显示出通过细胞内DFA III降解酶将DFA III转化为菊二糖。用全细胞反应从DFA III生产菊粉是可能的。罗氏链霉菌（Streptomycesrochei）E87产生一种胞外酶，以胞外方式将菊粉降解为菊粉三糖。对该酶进行了纯化，并对其酶学性质进行了研究.从莱万生产寡聚果糖：发现剥离链霉菌F3-2和节杆菌nicotinovorans SG 9分别产生果聚糖二糖和DFA IV。对果聚糖二糖产生酶进行了纯化，并对其酶学性质进行了研究.通过降解酶的转移反应生产低聚糖：节杆菌MS 9产生一种产生果聚糖二糖的酶，该酶通过β 2 -6键将菊粉二糖的果糖残基转移到菊粉二糖的还原末端果糖，形成一种新的三糖。

Oligo-saccharides attract much attention for their physiological function such as anticarious activity, prevention of constipation and of accumulation of plasma cholesterol, and low calorie sweetener etc. It has also been shown that oligo-saccharides are excellent health-care compounds for plants and microbes. As the importance of oligo-saccharides is recognized, it is apparent that development of their production methods becomes important. Thus, we initiated to study oligo-saccharides production by microbial processes using inexpensive starting materials such as inulin and levan. We isolated many microbes degrading inulin or levan from soil samples, and screened oligo-saccharides producers.1. Oligo-saccharides production from inulin : Arthrobacter sp.H65-7 producing difructose anhydride III (DFA III) was shown to convert DFA III into inulobiose by an intracellular DFA III-degrading enzyme. Inulobiose production from DFA III is possible with whole cell reaction. Streptomyces rochei E87 was found to produce an extracellular enzyme degrading inulin into inulotriose in an exo-manner. We have purified this enzyme and clarified its enzymatic properties.2. Oligo-saccharides production from levan : Streptomyces exfoliatus F3-2 and Arthrobacter nicotinovorans SG9 were found to produce levanbiose and DFA IV,respectively. Levanbiose-producing enzyme was purified and its enzymatic properties were investigated.3. Oligo-saccharides production by transfer reaction of degrading enzyme : Arthrobacter sp.MS9 produces a levanbiose-producing enzyme that transfer fructose residue of inulobiose to reducing-terminal fructose of inulobiose by beta2-6 linkage forming a novel trisaccharide.