Abstract: L-Phenylalanine is isolated in pure form from an aqueous solution thereof containing cinnamic acid by subjecting the aqueous solution to toluene extraction to extract cinnamic acid therefrom; separating the toluene phase; and then concentrating the aqueous phase, until crystals of L-phenylalanine form therein, while concurrently separating the crystalline L-phenylalanine from the liquid aqueous phase.

Abstract: A process for purifying tryptophan so as to contain almost no unreacted indole and a process for recovering unreacted indole with a very high percentage are provided, the purification process comprising passing a reaction fluid of tryptophan prepared from indole as raw material by means of an enzyme function, through a porous type, cation exchange resin layer, to cause the ion exchange part of the resin to absorb tryptophan, while to cause the porous part of the resin to adsorb indole, followed by eluting only the tryptophan with an alkali or acid aqueous solution, and the recovery process comprising subjecting tryptophan to repeated treatments of adsorption onto and elution from the ion exchange part of the resin and regeneration followed by eluting indole adsorbed onto the porous part of the resin with a water-containing organic solvent miscible with water and isolating indole from the resulting elute.

Abstract: From the aqueous solution containing cysteine obtained by the enzymatic method or fermentative method, cystine is produced in a high yield by oxidizing the cysteine in the presence of dimethyl sulfoxide.

Abstract: Disclosed is a method for separating lycine and L-serine from a solution containing both of them in the dissolved state and, in particular, a reaction solution obtained from a fermentation or enzymic conversion process for the preparation of L-serine by using glycine as the raw material. This method is based on a chromatographic technique utilizing the differential affinity of L-serine and glycine for a strongly acidic ion exchange resin.

Abstract: An anthraquinonic dye of the formula ##STR1## is provided. When used as dichloric dyes in liquid crystalline color display elements, these dyes (1) have sufficient coloring ability in small amounts, (2) have a high dichloric ratio, (3) are fully soluble in liquid crystals, and (4) have excellent durability, are stable and do not degrade the performance of a display device upon long-term use.