GB804970A - Improvements in or relating to the purification of lysine - Google Patents

Abstract

An impure aqueous solution of lysine or a water-soluble salt thereof containing amine impurities including one or both of di- and tri-(5-amino-5-carboxypentyl) amine is purified by passage through a strongly oxidic cationexchange resin, removing at least part of said amine impurities from the resin and subsequently removing lysine of increased purity from the resin. The purification may be effected in two preferred ways. Using low lysine loading of the resin, the solution is passed through a bed of resin in the acid or ammonium form, preferably the former, to absorb lysine and impurities, and the latter selectively eluted with dilute aqueous ammonia, preferably of concentration 0.1-0.7 per cent NH3, through an unloaded portion of the bed in the ammonium form, such unloaded portion preferably being at least one-third the length, more preferably one to two times the length of the loaded portion; the lysine remaining on the resin is subsequently eluted. Using high lysine loading of the resin, the solution is passed through a bed of the resin in the ammonium form until the bed is substantially completely loaded with lysine and preferably overloaded, preferably until 0.1-15 per cent, more preferably 2-10 per cent, of the lysine fed to the column has passed into the effluent. After a water wash, the lysine is eluted from the resin. The elution of lysine is preferably effected with aqueous ammonia of strength 5-29 per cent NH3. Preferably room temperature is used. Suitable resins are those having strongly acidic functional groups such as sulphonic, phosphonic or phosphorous acid groups. Preferred resins are the sulphonic acid type such as sulphonated coals, sulphonated phenol-aldehyde resins and nuclear sulphonated aromatic hydrocarbon resins. Particularly preferred are the nuclear sulphonated aromatic hydrocarbon cross-linked resins such as the sulphonated copolymers of a monovinylbenzene and a polyvinylbenzene, particularly sulphonated styrene-divinylbenzene copolymers having the equivalent of from 4-16 per cent divinylbenzene. The resin is used in particulate form, generally of 20-100 mesh, and preferably of 20-50 mesh (U.S. Standard screen scale). Repeated purification and re-cycling may be employed. Examples describe various procedures of the process of the invention.