Patent GB-698113-A (GB)
Title: Method for the isolation and purification of streptomycin
Filed: 1948-11-06
Abstract: A process of recovering streptomycin from an aqueous solution thereof comprises passing such aqueous solution in a condition adjusted to the alkaline side of neutrality through a column containing activated carbon, said carbon thereby adsorbing said streptomycin, passing an acidic aqueous solution through the column thereby eluting the streptomycin, passing absolute methanol through the column followed by water, thereby regenerating the carbon, and repeating the foregoing cycle.  The process may be applied to the recovery of streptomycin from filtered fermentation broths of which the pH is preferably adjusted to about 7.0 to 9.5. The column is washed with water and then with aqueous methanol. The streptomycin may be eluted with aqueous or aqueous alcoholic solutions of hydrohalic acids, sulphuric acid or formic acid of 1 to 2.5 normality, followed 0.1 normal acid (in 30 per cent aqueous methanol).  Streptomycin is collected while the pH of the effluent is between 6 and 3.  When the pH reaches 3 residual streptomycin is recovered by passing 30 per cent aqueous methanol (without acid), and the column is then regenerated.  The effluent containing streptomycin hydrochloride is adjusted to pH about 6.0 to 6.5, evaporated to 20 to 25 per cent solids and dehydrated by distillation with methanol, and the streptomycin hydrochloride precipitated by adding acetone. Alternatively the methanol solution can be chromatographed on alumina or converted to a crystalline calcium chloride complex.  In an example a streptomycin broth of pH7 is passed through a column of activated carbon which has been wetted and from which air has been removed. The column is washed with water, preferably with the same contact time as for both, then with aqueous methanol and the streptomycin is then eluted, firstly with normal hydrochloric acid in 30 per cent methanol solution and then with 0.1 normal hydrochloric acid. The effluent is collected while its pH falls from 6 to 3, this containing 85 to 95 per cent of the absorbed streptomycin, and residual streptomycin is recovered by washing with 30 per cent aqueous methanol.  The column is then made ready for reuse by washing with methanol until the effluent is colourless (which may elute up to 5 per cent of the adsorbed streptomycin), and then with water containing a trace of sodium hydroxide to bring the pH of the effluent to neutrality.  Specification 619,566 is referred to.  The Specification as open to inspection under Sect. 91 comprises generally a process for the adsorption of streptomycin on a column of activated carbon followed by its elution therefrom.  It is stated that a concentration of 50,000 units of absorbed streptomycin per gram of carbon is obtained.  The pH of the broth p  may be between about 5.0 and 9.5.  In an example a streptomycin broth is adjusted to pH about 7.9 with sodium hydroxide and passed through a column of activated carbon, the spent broth showing no streptomycin content. The absorbed streptomycin is eluted with 2.5 normal aqueous hydrochloric acid followed by 30 per cent methanol.  A table shows the streptomycin content of three fractions of eluant.  This subject-matter does not appear in the Specification as accepted.