Abstract: Disclosed is a process for preparing L-threonine which comprises causing D-threonine-aldolase, or D-threonine-aldolase and L-allothreonine-aldolase to act on a solution containing at least DL-threonine thereby obtaining L-threonine from a mixture containing at least DL-threonine.

Abstract: A process for producing an immobilized enzyme composition comprises simultaneously reacting a non-proteolytic enzyme and a water soluble-multifunctional reagent with a non-hardened granular gelatin in an aqueous medium wherein the reacting is carried out in the presence of a water-soluble protein polymer compound in an amount of from 0.01 to 2 parts by weight relative to one part of the non-proteolytic enzyme. The non-proteolytic enzyme forms a uniform film on the surface of the granular gelatin and the bond between the non-proteolytic enzyme and the granular gelatin is strengthened by the water soluble protein polymer.

Abstract: Immobilized enzyme compositions for industrial use are produced by reacting an enzyme and/or enzyme-containing microorganism cells with an anion-exchange high molecular substance having a quaternary pyridine ring in the molecule, and then subjecting the reaction products to molding and drying in a molding machine. A polyfunctional crosslinking agent may be added at any stage of the process. The immobilized enzyme compositions thus prepared can be packed in a reactor of an industrial scale for continuous enzyme reaction.