PRODUCTIONPROCESSOFS-PHENYL-L-CYSTEINE

PURPOSE: A process for producing S-phenyl-1-cysteine is provided to obtain S-phenyl-1-cysteine useful as an intermediate of pharmaceuticals and agricultural compounds with a higher purity and a greater yield. CONSTITUTION: The process for producing S-phenyl-L-cysteine comprises the steps of: (a) adjusting the pH of an enzymatic reaction mixture containing crystals of S-phenyl-L-cysteine to an acidic level, so that the crystals of S-phenyl-L-cysteine precipitated in the reaction mixture are dissolved; (b) adding activated carbon to the reaction mixture and then maintaining the resultant reaction mixture while aerating with an oxygen-containing gas, whereby a solid matter and unreacted thiophenol are adsorbed on the activated carbon and unreacted thiophenol not adsorbed on the activated carbon is insolubilized; (c) removing the activated carbon and insolubilized matter from the reaction mixture to obtain an S-phenyl-L-cysteine solution; and (d) adding an alkali to the S-phenyl-L-cysteine solution to precipitate crystals of S-phenyl-L-cysteine, and then recovering the crystals of S-phenyl-L-cysteine.