Description
White, odorless crystals or crystalline powder having a slightly
bitter taste. It is soluble in water, very slightly soluble in alcohol,
and insoluble in ether. It melts with decomposition between about
277° and 288°C.
Occurrence
Reported found in water bread, macaroni, egg noodles, corn flakes, corn grits, oatmeal, wheat bran, wheat
flakes, shredded wheat, barley, brown rice, rye flour, whole grain wheat flour, buttermilk, blue cheese, cheddar cheese, cottage
cheese, cream cheese, Parmesan cheese, bacon, cured ham, frankfurters, pork sausage, canned red kidney beans, canned sweet corn,
canned peas, canned lima beans, canned potatoes, almonds, cashews, peanuts, dates, beef, lamb, veal, chicken, turkey and other
natural sources
Biotechnological Production
L-Histidine is grouped with the aromatic amino acids, but the metabolic route
diverges at an early stage from the other members of the group. It is produced in
C. glutamicum in a 10-step sequence starting from phosphoribosyl pyrophosphate. Originally production titers of up to 10.5 g/L were reported, but this has
since been increased by workers at Kyowa Hakko to 22.5 g/L. In a parallel
development, the fermentation of L-histidine using E. coli has been reported by
Ajinomoto, with titers up to 19.1 g/L. Both the titer and the carbon yield for
L-histidine are lower than those reported for L-phenylalanine and L-tryptophan, and
L-histidine remains one of the more challenging amino acids to produce on an
industrial scale.
Purification Methods
A likely impurity is arginine. S-Histidine is adsorbed from aqueous solution onto a Dowex 50-H+ ion-exchange resin, washed with 1.5M HCl (to remove other amino acids), then eluted with 4M HCl as the dihydrochloride. This purified dihydrochloride (see below) is finally dissolved in water, the pH adjusted to 7.0, and the free zwitterionic base crystallises out on addition of EtOH. Its solubility in H2O is 4.2% at 25o. [Greenstein & Winitz The Chemistry of the Amino Acids J. Wiley, Vol 3 pp 1971-1993 1961, Beilstein 25 III/IV 4344.]
