Analysis on the novel phenomenon in the enzymatic degradation of insoluble polysaccharide, especially of starch granule, was done to obtain the fundamental results as follows.
(1) Starch granules from various botanical sources were classified into three types of groups by the susceptibility to digestion of glucoamylase.In the initial stage of reaction, 10-40% of total glucose produced was found in the granule, which was termed "product fixation." As for alpha-amylasc, about 10% of product was in the granule. The most product fixation was observed in the isoamylase-catalyzed digestion, giving 30-60% product inside.
(2) The starches most resistant against glucoamylase digestion, potato, shoti, amylomaize-7, were heated at their gelatinization temperatures to prepare the gelatinized starches.The gelatinized starches showed the 2-to 15-fold higher susceptibility to amylases hydrolysis than native ones with no change in the ratio of product which bound to granules.
(3) The product fixation of isoamylase-catalyzed hydrolysis on the gelatinized starches was investigated. To the reaction mixture, ethanol was added to change the hydrophobicity. The amount of product in granule increased with the increase in the concentration of ethanol. Ethanol concentration of 80% gave the complete fixation of product. The effects of reaction temperature on the product fixation were examined, elucidating that at low temperature more product was in the gelatinized starches.
The findings shows 1) that the product of long chain gave the high degree of product fixation, 2) that the mild structural change of starch granule given by heating in gelatinization temperature increased the susceptibility to amylases digestion and retained the fixation of product, and 3) that hydrogen bond was considered to contribute the product fixation mainly since the amount of product increased at low temperature and in the highly hydrophobic condition.