METHOD OF CITRIC ACID PRODUCING Russian patent published in 2002 - IPC

FIELD: biotechnology, biochemistry. SUBSTANCE: method of producing citric acid involves hydrolysis of starch suspension comprising 26-30 wt.% of dry matter with an enzyme preparation of bacterial α-amylase taken in the amount 1.5-2.0 U of amylolytic activity/1 kg of dry starch matter. Hydrolysis is carried out at increased temperature and under excessive pressure, it involves addition of mineral salts to starch hydrolyzate as zinc, iron (II), copper sulfates taken in the amount (2.0-7.0) x 10^-3 g/dm³ of starch hydrolyzate and the following fermentation of nutrient medium with fungus Aspergillus niger. After fermentation and separation of fungus biomass the cultural fluid containing 84.9-88.5 wt.% of citric acid and acid-resisting enzymes α-amylase and glucoamylase is obtained. Method ensures to obtain a cultural fluid showing the enhanced amylolytic activity of acid-resisting enzymes α--amylase and glucoamylase and activity of these enzymes is estimated to be 0.62-0.69 and 22.5-28.6 U of amylolytic activity/cm³, respectively. EFFECT: improved method of producing. 1 tbl