GB721484A - Improvements in or relating to the degradation of dextran - Google Patents

Abstract

An aminoacid-stimulated dextran-acclimated enzyme which degrades dextran in an aqueous medium (see Group V), is obtained by cultivating an Aspergillus mould, e.g. a strain of Aspergillus Wentii in a nutrient solution containing dextran (see Group VI). The enzyme may be separated from the culture medium by filtration and precipitated from the filtrate by adding acetone or dioxane. Alternatively, the enzyme may be salted out by adding ammonium sulphate, sodium sulphate or sodium chloride to the filtrate. The precipitate may be dried to yield a powder.ALSO:In making dextran of low molecular weight from dextran of relatively high molecular weight, an aminoacid-stimulated, dextran-acclimated enzyme from an Aspergillus mould, e.g. a strain of Aspergillus Wentii (see Groups IV(b) and VI) is mixed with dextran of high molecular weight in an aqueous medium, the mixture is kept until the desired degree of degradation is attained and dextran of low molecular weight is removed, e.g. precipitated by adding to the degraded mixture an organic precipitant such as alcohol. The degraded mixture may first be separated into layers by adding acetone and a degraded dextran fraction may then be precipitated from each layer. The precipitate may be dissolved in water and reprecipitated. The precipitates may be dried in vacuo. The action of the enzyme may be stopped by bringing the pH of the mixture into the range of about 2.0 to 3.0 or 9.0 to 10.0, e.g. when the viscosity of the mixture relative to water is 2.0. The enzyme may be added to a medium containing about 7 per cent. of dextran.ALSO:An Aspergillus mould, e.g. a strain of Aspergillus Wentii is cultivated in an aqueous nutrient solution containing dextran, e.g., from 5.0 to 50 g dextran per litre, and a source of aminoacids so that a dextran-acclimated, aminoacid-stimulated enzyme (see Group IV(b)) is produced. This enzyme is used to degrade dextran (see Group V). The nutrient solution may contain the following substances in g. per litre; peptone 5.0, dextran 10.0, magnesium sulphate 0.1, sodium chloride 0.1, ferrous sulphate 0.1, sodium chloride 0.1, ferrous sulphate 0.01, manganous sulphate 0.01, potassium dihydrogen phosphate 0.1, sodium acetate 2.0, potassium acetate 0.5, with or without the following vitamins in m.g. per litre :-nicotinic acid 1.0, riboflavin 0.5, thiamine 0.5, calcium pantothenate 0.5, pyridoxine 0.4, folic acid 0.01, biotin 0.001. The peptone may be replaced by 5.0 g casein hydrolysate per litre. The vitamins may be replaced by 0.4 g. yeast extract per litre.