| Budget Amount *help |
¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 1999: ¥1,000,000 (Direct Cost: ¥1,000,000)
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| Research Abstract |
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.
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