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UTILIZATION OF ACID-STABLE A-AMYLASE FROM THE CITRIC ACID KOJI (Aspergillus usamii var.) AND PREPARATION OF EDIBLE MICROCAPSULE

柠檬酸曲(Aspergillus usamii var.)酸稳定性α-淀粉酶的利用及可食性微胶囊的制备

基本信息

批准号：
10660131
负责人：
SUGANUMA Toshihiko
金额：
$ 0.64万
依托单位：
KAGOSHIMA UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 1999
项目状态：
已结题

项目摘要

In Kagoshima, citric acid was produced on a commercial basis by a koji of a variety of Aspergillus usamii, using waste pulp of sweet potato from starch production factories. For the utilization of by-product purified enzyme of acid-stable a-amylase (UAA) was obtained from the acidic extract of the koji by column chromatograph. The enzyme exhibited its optimum activity a pH of around 3-5.5 (at 37℃), and a temperature of 60-70℃ (at pH4.0), which is about 15℃ higher than the ordinary neutral a-amylase (NA). The sequence of the first 20 amino acids from the N-terminus as well as a molecular weight of about 100,000 differed from the ordinary NA. Using a series of maltooligosaccharides labeled with 14C-glucose at the reducing end, the rate parameter k0/Km and the cleavage frequency were determined. It was elucidated that the active center is composed of five subsites, with the catalytic site located between the 3-rd and the 4-th subsites from the nonreducing end. Chemical modification was performed to elucidate the role of the amino acids in the active site of a-amylase. A new substrate Gal-G3-CNP was synthesized by galactosylation of commercial G3-CNP, and allowed us to discriminate between UAA and NA even in the presence of glucoamylase. UAA was found to enhance the rate of digestion of raw starch by glucoamylase. Thus, the digested starch was prepared as a new starchy material of edible microcapsule from corn starch by digestion with the crude extract of the koji. No change in chemical structure was found such as distribution of chain length of the digested starch, while the significant change in the physical properties was found such as α-amylase digestibility and the maximum viscosity in amylogram. Incorporation experiment with the digested starch and the dye compounds revealed that the cavity of starch granule produced by the digestion absorbed cationic compounds easier than anionic compounds.

在鹿儿岛，柠檬酸是在商业基础上生产的各种曲霉宇佐美曲，使用废纸浆的甘薯淀粉生产厂。为了利用副产物，采用柱层析法从酒曲的酸性提取液中分离纯化了耐酸性α-淀粉酶（UAA）。该酶的最适反应温度为60-70℃（pH4.0），最适pH为3-5.5，比普通中性α-淀粉酶（NA）高15℃左右。从N-末端开始的前20个氨基酸的序列以及约100，000的分子量与普通NA不同。利用还原末端标记有14 C-葡萄糖的一系列麦芽低聚糖，测定了速率参数k 0/Km和切割频率。结果表明，活性中心由5个亚中心组成，催化中心位于从非还原端起的第3和第4个亚中心之间。对α-淀粉酶活性中心的氨基酸进行化学修饰，以阐明其作用。通过半乳糖基化商业G3-CNP合成了一种新的底物Gal-G3-CNP，即使在葡糖淀粉酶的存在下，也允许我们区分UAA和NA。UAA能提高糖化酶对生淀粉的消化率。因此，以玉米淀粉为原料，用曲粗提物进行酶解，制备了一种新型的可食性微胶囊淀粉原料。酶解淀粉的化学结构如链长分布没有变化，而物理性质如α-淀粉酶消化率和淀粉谱中的最大粘度有显著变化。淀粉与染料化合物的掺入实验表明，淀粉颗粒在消化过程中产生的空腔更容易吸收阳离子化合物而非阴离子化合物。