METHOD FOR PREPARING CITRIC ACID Russian patent published in 2003 - IPC

FIELD: microbiological industry. SUBSTANCE: invention relates to preparing and acid-resistant enzymes: α--amylase and glucoamylase from starch-containing raw. Method involves starch hydrolysis with enzyme preparation of bacterial α--amylase at enhanced temperature and under excessive pressure, addition of mineral salts to starch hydrolyzate and the following fermentation of medium with an acid-producing fungus Aspegillus niger. To the nutrient fermentation medium mineral salts are added additionally in the form of copper (II), zinc, cobalt (II) sulfate in the amount (0.5-1.0) x 10^-3, (1.5-3.5) x 10^-3 and (1.5-4.5) x 10^-3 g/dm³, respectively, starch hydrolyzate and organic source of nitrogen in the amount providing the content of carbon and nitrogen in the ratio = (65-75) : 1, respectively. Invention provides conversion of sugars to citric acid at the level 79.5-83.2% and preparing acid-resistant enzymes: α-amylase and glucoamylase with activity 0.80-1.25 U A.C/cm³ and 32.6- 78.7 U A.C/cm³, respectively. EFFECT: improved preparing method, high yield of products. 1 tnl, 5 ex