GB774961A - Improvements in or relating to production of tyrosine - Google Patents

Abstract

L-Tyrosine is obtained in an improved crystalline form by admixing with an aqueous solution containing tyrosine (preferably between 5 and 15 grams per litre), sufficient non-oxidizing mineral acid, preferably HCl, to adjust the pH of said solution to between 1.3 and 2.2, heating the resulting solution to between 50 DEG and 100 DEG C., preferably between 70 DEG and 90 DEG C., until substantially all of the tyrosine has dissolved and allowing the hot solution to cool at an average rate of less than 0.25 DEG C. per minute to a temperature between atmospheric temperature and 60 DEG C., when the tyrosine crystallizes out. After separation of the tyrosine crystals, the mother-liquors are recycled by the addition of more tyrosine. The crystals (glossy white needles) have a size up to about 2.5 mm. by about 0.015 mm. (average size 0.2 mm. X 0.015 mm.) and the ratio of length/width is from 20:1 to 5:1. In examples: (1) tyrosine is mixed with water and acidified with HCl to pH 1.8, decolorising carbon is added, and the mixture heated and stirred at 85 DEG C. for 10 minutes, filtered hot and allowed to cool without agitation, yielding tyrosine as needles, which are washed and dried at 105 DEG C.; (2) tyrosine is dissolved in mother-liquors from (1) and the solution treated as before.