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Aspergillus niger KCTC 1230이 생산하는 생전분 분해효소
금인경,정만재 충북대학교 농업과학기술연구소 1998 農業科學硏究 Vol.15 No.-
In order to search for powerful raw starch digesting enzyme, Aspergillus niger KCTC 1230 was selected as a strain. Experiments were conducted to investigate the conditions of the glucoamylase production, the purification procedures of the enzyme, some characteristics of the purified enzyme and hydrolysis rates on various raw starches, such as com, rice, potato, glutinous rice, sweet potato, wheat and barley. 1.The optimum temperature and time for the enzyme production on wheat bran medium were 30℃ and 96 hrs, respectively. The additions of diammonium hydrogen phosphate, casein, lactose, maltose, fructose and soluble starch on wheat bran medium increased slightly the production of the enzyme. 2.The enzyme was purified by ammonium sulfate fractionation and DEAE-cellulose column chromatography. The specific activity of the purified enzyme was 34.1 U/㎎ protein and the yield of enzyme activity was 13.3%. 3.The purified enzyme showed a single band on polyacrylamide disc gel electrophoresis and its molecular weight was estimated to be 58,900 by SDS-polyacrylamide disc gel eletrophoresis. The isoelectric point of the prufied enzyme was pH 3.9. 4.The optimum temperature and pH were 65℃ and pH 4.5, respectively, and the purified enzyme was stable in the pH range of 4.0-10.5. The purified enzyme was stable at up to 40℃ and its thermostability was slightly increased by the addition of Ca2+. 5.activity of the purified enzyme was increased by Mn2+, Fe2+, Ca2+, but it was decreased by Hg2+, Pb2+, Co2+, Ba2+, I2, Naf. 6.The purified enzyme showed a high rate of hydrolysis on various raw starches, such as corn, rice and glutinous rice. The enzyme showed 53% hydrolysis rate even on raw potato starch, one of the most difficult starches to be hydrolyzed. 7.The raw starch digesting enzyme from Aspergillus niger KCTC 1230 was identified as the gluocoamylase.