Abstract: The objective of the present invention is to provide a method of producing each high purity imidazole dipeptide in large quantities on an industrial scale, regardless of the type of animal extract employed. The objective is achieved by a method of producing a purified imidazole dipeptide composition, including the step (1) of subjecting an animal extract treatment solution containing at least two types of imidazole dipeptides to adsorption treatment carried out by bringing the solution into contact with a hydrophobic adsorption resin to adsorb the imidazole dipeptides onto the hydrophobic adsorption resin; and the step (2) of subjecting the hydrophobic adsorption resin adsorbing the imidazole dipeptides to elution treatment using an aqueous solution to mutually separate and collect the imidazole dipeptides to purify an imidazole dipeptide.

Abstract: It is an objective of the present invention to provide a method of producing imidazole dipeptides that reduces burden and time for an elution treatment when compared to the prior arts, and furthermore, that can produce high purity imidazole dipeptides with less contamination of creatinine. The above objective is achieved by a method of producing high purity imidazole dipeptides, comprising: (1) subjecting an animal extract containing imidazole dipeptides and creatinine to an ion adsorption treatment in which the animal extract is brought into contact with a strongly acidic cation exchange resin having an alkali metal salt type of ion exchange group at a predetermined pH value to adsorb the imidazole dipeptides onto the resin; and (2) subjecting the strongly acidic cation exchange resin adsorbing the imidazole dipeptides to an elution treatment with the use of an aqueous alkaline solution and at a predetermined pH value to obtain high purity imidazole dipeptides.

Abstract: Succinic acid is produced by bringing a succinic acid-containing liquid containing succinic acid and cation which is obtained by fermentation or an enzymatic method into contact with an H-type strongly acidic cation-exchange resin in an amount equivalent to or more than the amount of cation other than hydrogen ion contained in the succinic acid-containing liquid, and precipitating a crystal of succinic acid from the obtained ion-exchange-treated liquid to obtain purified succinic acid.

Abstract: A method for purifying an amino acid selected from the group consisting of valine, leucine and isoleucine easily in high yield and with high purity using an inexpensive precipitant, comprising allowing p-ethylbenzenesulfonic acid or its water-soluble salt to act on an aqueous solution containing an amino acid to form crystals of the amino acid p-ethylbenzenesulfonate and then separating and decomposing the crystals to purify and obtain the amino acid. The p-ethylbenzenesulfonic acid may be used as the free acid, an alkali metal salt and an ammonium salt.

Abstract: A process is provided for obtaining high-purity valine in high yield by a simple method using an inexpensive precipitant of p-isopropylbenzene sulfonic acid or a water-soluble salt thereof.

Abstract: A method of obtaining optically active anhydrous phenylalanine crystals from an aqueous solution containing optically active phenylalanine, which involves crystallizing and precipitating optically active phenylalanine from an optically active phenylalanine super-saturated solution at a temperature, T, wherein the super-saturated solution is required to have an osmotic pressure .pi. (mOsm/kg.H.sub.2 O) which is related to said temperature T in accordance with the following formula (I):.pi..gtoreq.10,500-450T+4.4T.sup.2 (I),wherein the method provides anhydrous crystals having excellent handleability.

Abstract: A feed additive produced by concentrating an aqueous solution containing tryptophan and impurities both originating in the culture broth of a tryptophan-producing microorganism, with the pH of the aqueous solution being maintained in the range of 4 to 6 and the temperature thereof being maintained in the range of 20.degree. to 80.degree. C. during the process of concentrating.

Abstract: A process for refining phenylalanine, in which a phenylalanine solution containing tyrosine as the main impurity and other impurities is contacted with a non-polar, highly porous synthetic adsorbent, adsorbing phenylalanine on the adsorbent selectively, and eluting and recovering the adsorbed phenylalanine, is disclosed.