GB775948A - Production of endo-dextranase by an aspergillus mold - Google Patents

Abstract

A filtrate containing dextranase having the capacity to attack glucosidic linkages of large dextran molecules to thereby split the large molecules into relatively low molecular weight segments is obtained by inoculating an Aspergillus mould in an aqueous nutrient medium comprising dissolved metallic salts and, per litre of water, 2.0 to 5.0 grms. of amino acids or protein sources of amino acids, 5.0 to 50 grms. of dextran as the sole carbohydrate, incubating at a pH of 7 to 7.5 and separating the dextranose from the mat mould by filtration. The metallic salts are preferably present in quantities of 2.0 to 5.0 grms. per litre. The amino acids may be in the form of peptone or protein hydrolysates such as casein hydrolysate. The nutrient medium preferably also contains vitamins of the B complex, e.g. in the form of yeast extract, and in concentrations of 2.5 to 5.0 mg. per litre. The temperature is room temperature and the duration of incubation may be 80 hours. Specified Aspergilli are A. usutus, A. candidus, A. niger, A. tamaric, A. flarus-oryzal and A. Wentii, which is preferred. A preferred nutrient medium consists of an aqueous solution of peptone, dextran, magnesium sulphate, sodium chloride, ferrous sulphate, manganese sulphate, potassium hydrogen phosphate, sodium acetate, potassium acetate, nicotinic acid, riboflavin, thiamine, calcium pantothenate, pyridoxine, folic acid and biotin. The dextranase may be recovered from the filtrate as a white powder by precipitation with organic solvents such as acetone, alcohols and dioxane or by salting out with an inorganic salt such as ammonium sulphate, sodium sulphate or sodium chloride followed by dialysis to remove extraneous salts. A combination of these steps is preferred.ALSO:An aspergillus mould is cultivated in an aqueous nutrient medium at a pH of 7 to 7.5 in order to produce dextranase, the said medium comprising dissolved metallic salts, and, per litre of water, 2.0 to 5.0 grms. of amino or protein sources of amino acids, and 5.0 to 50 grms of dextran as the sole carbohydrate. The metallic salts are preferably employed in quantities of 2.0 to 5.0 grms per litre. The amino acids may be in the form of peptone or protein hydrolysates sluch as casein hydrolypate. The nutrient medium preferably also contains vitamins of the B complex e.g. yeast extract, and in concentrations of 2.5 to 5.0 mg per litre. The incubation temperature is that of the room and the duration is 80 hours. Specified aspergilli are A usutus, A candidus, A niger, A tamaric, A flarasorizal and A wentii. A prepared medium consists of an aqueous solution of peptone, dextran, magnesium sulphate, sodium chloride, ferrous sulphate, managanese sulphate, potassium hydrogen phosphate, sodium acetate, potassium acetate, nicotinic acid, riboflavin, thiamine, calcium pantothenate, pyridoxine, folic acid and biotin.