The enzymatic properties of glucoamylase fixed on polyacrylonitrile carrier resin by amidination reaction were studied. Following results were obtained; The optimum pH for the fixed glucoamylase (pH 5.5) was found to be 0.7 pH units higher than that for the native glucoamylase (pH 4.8). And the slight shift of the optimum pH to acidic side were observed when the fixed glucoamylase were stored in distilled water at 4°C before the test runs. The optimum temperature for the fixed glucoamylase (ca. 55°C) was lower than that for the native glucoamylase (ca. 60°C). To understand said changes in the enzymatic activity of the fixed glucoamylase, the apparent thermodynamic quantities in terms of the LINEWEAVER-BURK plots at various pH and temperature were compared between native and fixed glucoamylase. The value of the apparent MICHAELIS constants (K_m) for the fixed glucoamylase was found to be higher than that for the native glucoamylase, indicating the external diffusion effect of the substrate (soluble starch). The apparent activation energy of the fixed glucoamylase (12.9 kcal/mol) was observed to be a little higher than that of the native glucoamylase (10.4 kcal/mol) at pH 5.0. And the mentioned differences were suggested to recover to a certain extent provided that some treatments such as storage in distilled water at 4°C and etc. were conducted before the test runs.

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Adsorption behavior of organic compounds on dry amylose powder in organic solvents was investigated. (1) It was found that the adsorption of monobasic fatty acids in n-hexane followed LANGMUIR's adsorption isotherm. Maximum adsorbed quantities and adsorption coefficients of 14 kinds of fatty acids were estimated at 25°C. The former values (mM/g amylose) decreased with the increase of the number of carbon atoms in fatty acid molecule up to 8-9 and were almost constant thereafter. (2) Four kinds of adsorbents, native potato and corn starches, gelatinized potato starch and potato amylose, were tested for the adsorption of ethanol in n-hexane, carbon tetrachloride and benzene. The weight of ethanol adsorbed by the amylose was much greater than that by the other adsorbents. (3) Adsorption of methanol and ethanol in 5 kinds of solvents and adsorption of 14 kinds of organic compounds in n-hexane were tested. It seems likely that the adsorbed quantity increased with increasing dielectric constant ratio [ε(adsorbate)ε/E (solvent)].

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In order to clarify the changes of physicochemical properties of irradiated starch, amylomaize starch treated with gamma rays up to 10 Mrad, was examined for its decomposition products and former products compared with those of normal corn starch. 1. After irradiation with gamma rays, amylomaize and normal corn starches showed a rapid decrease in amylogram viscosity, and a decrease in iodine absorption and pH with increasing of radiation dose. But they did not show any changes in X-ray diffraction patterns. 2. In the elution patterns of irradiated starches on Sephadex G-75 column, starch fraction was found to decrease with increasing of radiation dose. Amylomaize and normal corn starches irradiated with a dose of 10 Mrad decreased in starch fraction approximately by 30% and 50% respectively as compared with that of non-irradiated starches. 3. Cold water soluble fraction and reducing sugars of irradiated starches increased with increasing of radiation dose. Cold water solubilities of irradiated amylomaize and normal corn starches with a dose of 10 Mrad were 0.67% and 1.46% respectively. Reducing sugars occupied about 10% of cold water soluble fraction. This ratio was constant independent of radiation dose. 4. The molecular weight distribution of cold water soluble components produced with gamma irradiation was different between amylomaize and normal corn starches. Most of cold water soluble fraction of amylomaize starch was composed of the low molecular weight components, however, that of normal corn starch consisted of from low molecular weight to high molecular weight ones. Oligosaccharides up to DP 9 were separated by Bio-gel P-2 column from cold water soluble fractions of both irradiated starches. 5. Judging from the results above, both amylomaize and normal corn starches were degraded by gamma irradiation. However, amylomaize starch was less sensitive to this treatment than normal corn starch.

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By using a highly purified glucoamylase [EC 3.2.1.3] from Trichoderma viride, some properties of the enzyme were further investigated. The molecular weight of the enzyme was estimated to be about 75, 000 on the basis of SDS polyacrylamide gel electrophoresis. The Km and Vmax values at 30°C and pH5 .0 were calculated for the enzyme acting on glycogen, amylopectin, amylose, soluble starch, short chain amylose and maltose.

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By using the authentic anomers of D-glucopyranose under conditions limiting mutarotation, it was found that the condensation reactions catalyzed by glucoamylase require a donor substrate of specific configuration. A highly purified glucoamylase from Trichoderma viride, which hydrolyzes amylaceous substrates to β-D-glucopyranose, was found to catalyze the rapid synthesis of maltose and isomaltose specifically from p-n-glucopyranose. The configurational inversion accompanying the condensations indicates that the D-glucopyranosyl portion of a-D-glucopyranose is interchanged with hydrogen at the C₄ or C₆ carbinol site of a second n-glucose molecule (glucosyl transfer).

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In our previous paper, we observed that physico-chemical properties of starches treated by oxidized oil were enormously changed, especially in the temperature of gelatinization, swelling power, solubility, hardness and adhesiveness of paste. In this paper, we described the results of our model experiments using fatty acids and higher alcohols of carbon 6 and 8. By the addition of fatty acids and alcohols mentioned above the physico-chemical properties changed differently between corn and potato starches. The change of physico-chemical properties were discussed with the connection of introduction of carbon chain into starch molecules. These results coincided well that of the oxidized oil treatment of starches.

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