In the early process of retrogradation of cooked rice, the amount of the water-soluble fraction and the degree of gelatinization firstly increased, and thereafter continuously decreased. The presence of a few helical complexes of starch and fatty substances was indicated by the V type of X-ray diffraction pattern. A crystalline structure was recovered after disappearance of the helical complexes. In this study, the effects of fatty substances and the degree of gelatinization after heating on the above mentioned phenomenon were examined. The results were as follows.
1) The phenomenon was seen in the cases of retrogradation of rice, rice regenerated with fatty acid and rice starch, but not for defatted rice and defatted rice starch. The B type of X-ray diffraction pattern reappeared earlier for defatted samples than for non-defatted ones.
2) Even for non-defatted samples, when the degree of gelatinization was sufficiently high, the phenomenon was not observed, and when the degree was low, it was observed at a different stage, depending on the degree of gelatinization. The B type of X-ray diffraction pattern reappeared earlier for the samples showing low degrees of gelatinization than for ones showing high degrees.
3) During the retrogradation, the amount of the water-soluble fraction increased and then decreased with time, molecules with molecular weights of less than 10⁶ being remarkably water-insoluble.

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A high-performance gel chromatographic method for starches involving distilled water as a solvent and two columns (φ7-8mm×60-100cm) packed with Toyopearl HW gels (HW-75S and HW-75F, respectively) was developed. A solution of starch dissolved in 1N NaOH was passed through a column of Amberlite IR 120 (H⁺) to remove cations, and then stocked in an aqueous solution saturated with 1-butanol. Some starch components were separated excellently on the gel, and 1-butanol appeared after elution of these components.
Normal (n), waxy (wx), amylo (ae) and amylowaxy (ae wx) maize-starches were analyzed by this method and the results obtained were as follows:
(1) Chromatography of the starches was completed within 60min at a flow rate of 1ml/mm.
(2) Each starch showed a characteristic elution pattern; a shoulder peak on the amylopectin fraction and an increase in the amylose fraction were observed for the amylo starch, and a small amount of a low-molecular-weight material like amylopectin was observed for the amylowaxy starch.
(3) The recovery of starch was about 60-80%, and the fine (F) gel size gave a better recovery than superfine (S). A decrease in the recovery was caused by adsorption of amylopectin on the gel. Amylose applied was eluted almost completely from the column.
(4) High-performance gel chromatography on a column (φ8mm×100cm) of Toyopearl HW-75F was very useful for determination of the amylose content of a starch in a short time. The amylose contents of the normal and amylo starches were found to be 26% and 48% with this method, respectively.

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Aqueous soluble starch solutions (20%) were aged at 0-30°C for 24hr and the gelatinization behavior of retrograded starches was investigated by photopastegraphy and X-ray diffraction. Elevation of aging temperature resulted in the elevation of gelatinization temperature from 32°C to 50°C. The X-ray diffraction patterns of retrograded starches suggested that the gelatinization behavior is controlled by non-crystalline domains rather than by crystalline ones. Similar thermal properties were observed on the amylodextrins crystallized at various constant temperatures. The gelatinization temperature was increased a little by prolonged incubation but it was affected mainly on the aging temperature. These results suggest that the stronger hydrogen bonds were formed rapidly at the higher aging-temperature.

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An alkalophilic bacterium, which produces a significant amount of intracellular isomaltose-hydrolyzing α-glucosidase, has been isolated from soil using a high alkaline pH medium containing 1% NaHCO₃. The bacterium can grow within the pH and temperature ranges of 5.0-10.0 and 20-55°C, and very good growth was detected at nearly pH 9.0 and 45°C. The enzyme production was strongly enhanced through the induction mechanism by maltose and soluble starch. Maximal enzyme accumulation was attained during logarithmic bacterial growth in medium consisting of 1% soluble starch or maltose, 5% defatted soybean powder, 0.1% K₂HPO₄, 0.02% MgSO₄·7H₂O and 1% NaHCO₃, as a result of de novo protein synthesis. The enzyme was most active at pH 6.0-6.5 and 45°C.

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The gene coding for an oligo-1, 6-glucosidase of alkalophilic Bacillus sp. F5 was cloned into the EcoRV site of pBR322 and expressed in Escherichia coli HB101.
Plasmid pMC1, containing a 9.1Kb EcoRV fragment, was isolated from the α-glucosidase-positive transformant. Genomic hybridization showed that the 9.1Kb EcoRV fragment was derived from the chromosomal DNA of alkalophilic Bacillus F5. Restriction analysis showed that the oligo-1, 6-glucosidase gene was located in the 3.1Kb EcoRV-PvuII fragment. The enzyme productivity of the E. coli HB101 transformant carrying pMC21, which contains a 3.1Kb fragment, was about 13 times higher than that of the DNA donor strain.

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A spectrophotometric assay procedure for amylo-1, 6-glucosidase (EC. 3. 2. 1. 33) using 6-O-α-D-glucosyl cyclomaltoheptaose (glucosyl β-cyclodextrin) as a substrate was described in detail. The enzyme showed optimum activity around pH 6.3 and a Km of 8.3mM for glucosyl β-cyclodextrin, and produced β-D-glucose. The results of this assay well agreed with those of the assay involving the reverse reaction using [¹⁴C] glucose as a substrate.

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Some outlines of analyses of oligo- and poly-saccharides of low molecular weight (DP-40) by HPLC on NH₂- and C₁₈-bonded silica, and by TLC on silica gel 60 plates with a concentration zone, silica gel 70 TLC, Si 50000 HPTLC and NH₂ HPTLC plates were given.

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