METHOD FOR PREPARING CITRIC ACID AND ACID-STABLE AMYLOLYTIC ENZYMES COMPLEX Russian patent published in 2007 - IPC C12P7/48 C12N1/14 C12R1/685 

FIELD: microbiological industry, biochemistry.

SUBSTANCE: invention relates to a method for preparing citric acid and a complex of acid-stable amylolytic enzymes possessing activity of α-amylase and glucoamylase. Method involves separation of mycelium of fungus Aspergillus niger as a producer of acid from a fermented solution with the protein concentration 1.5-7.0 g/dm³ at temperature ≤32°C. Prepared fermented solution is purified by successive filtration processes through membranes with pores diameter values 0.65, 0.45 and 0.15 mcm and separated by ultrafiltration through a membrane retaining substances with molecular mass in limits 1000-50000 Da and providing preparing citric acid solution and acid-stable amylolytic enzymes solution. Citric acid solution with the protein content 0.05-0.15 g/dm³ is cleared preliminary followed by its concentrating, crystallizing and citric acid crystals are separated from mother liquor. Mother liquor with optical density value 0.1-0.4 at λ_max = 400 nm is recovered to the concentrating step and solution with optical density 0.41-0.8 at λ_max = 400 nm is cleared preliminary and recovered to the concentrating step. Solution of above mentioned enzymes is dried by sublimation or spraying up to preparing a dry complex with enzymatic activity of α-amylase and glucoamylase 700-900 and 10000-15000 U/g, respectively, or solution is precipitated followed by drying up to preparing the dry complex with enzymatic activity of α-amylase and glucoamylase 1000-1300 and 20000-26000 U/g, respectively. Method provides simultaneous preparing crystalline citric acid and a dry complex of acid-stable amylolytic enzymes with the high quality and high yield.

EFFECT: improved preparing method.

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