the desired reaction temperature and the desired pressure are established when the mixture is fed into the reactor the hydantoin containing solution preferably originates from the reaction mixtures obtained after synthesis and preferably already contains carbon dioxide the oxidic catalyst is used in various forms either in powder form shaped in the conventional manner or in the form of a fixed bed it has been found that tio 2 in the crystalline form anatase is particularly suitable in general the chosen catalyst is used in an amount of from gt 0 to 0 1 kg preferably from 0 001 to 0 05 kg based on 1 kg of the hydantoin used following the saponification of the hydantoin which is carried out continuously or batchwise ammonia and carbon dioxide are separated from the liquid phase in a suitable apparatus with a portion of the water in vapour form the portion of the water ammonia carbon dioxide mixture formed in the saponification reaction is preferably returned to the hydantoin synthesis or fed to the saponification process again in the desired amount the aqueous mixture obtained after separation generally contains from 10 to 40 wt based on the total amount of the desired u03b1 amino acid the u03b1 amino acid is crystallized out by known means and separated from the mother liquor the mother solution containing as yet unreacted hydantoins is returned to the hydrolysis process and mixed with fresh hydantoin containing solution upstream of the reactor the mother solution generally accounts for more than about 30 vol of the reaction mixture which contains a corresponding amount of fresh hydantoin containing solution in order to avoid the concentration of any by products which may be present from 1 to 2 vol of the mother liquor are generally discharged in the process according.