Abstract: An optically active 1,3-butanediol can be produced by either (1) treating a mixture of 1,3-butanediol enantiomers with a microorganism, which has been optionally treated, capable of asymmetrically assimilating said mixture, or (2) preparing a microorganism, which has been optionally treated, capable of asymmetrically reducing 4-hydroxy-2-butanone, and collecting optically active 1,3-butanediol.

Abstract: An optically active 1,3-butanediol can be produced by either (1) treating a mixture of 1,3-butanediol enantiomers with a microorganism, which has been optionally treated, capable of asymmetrically assimilating said mixture, or (2) preparing a microorganism, which has been optionally treated, capable of asymmetrically reducing 4-hydroxy-2-butanone, and collecting optically active 1,3-butanediol.

Abstract: An optically active 2-hydroxy acid derivative is produced by treating a 2-oxo acid derivative with a microorganism, which has been optionally treated, capable of asymmetrically reducing said 2-oxo acid derivative into an optically active (R)- or (S)-2-hydroxy acid derivative represented by the formula (II) and recovering the optically active (R)- or (S)-hydroxy acid derivative thus formed. Optically active 2-hydroxy acid derivatives are important intermediates in the synthesis of various drugs such as a remedy for hypertension.

Abstract: A microorganism or a preparation thereof is permitted to act on a mixture of enantiomers of 3-phenyl-1, 3-propanediol, and the residual optically active 3-phenyl-1,3-propanediol is harvested.The genera of those microorganisms which are able to leave (R)-3-phenyl-1,3-propanediol include Candida, Hansenula, Rhodotorula, Protaminobacter, Aspergillus, Alternaria, Macrophomina, Preussia and Talaromyces.The genera of those microorganisms which are able to leave (S)-3-phenyl-1,3-propanediol include Candida, Geotrichum, Leucosporidium, Pichia, Torulaspora, Trichosporon, Escherichia, Micrococcus, Corynebacterium, Gordona, Rhodococcus, Aspergillus, Emericella, Absidia, Fusarium, Dactylium, Serratia and Pseudomonas.

Abstract: Optically active 1,3-butanediol can be obtained by treating an enantiomorphic mixture of 1,3-butanediol with a microorganism or cells thereof which have been ground, acetone-treated, or lyophilized, capable of acting on an enantiomorphic mixture of 1,3-butanediol so as to leave (R)- or (S)-1,3-butanediol as such.Further, optically active 1,3-butanediol can be obtained by treating 4-hydroxy-2-butanone with a microorganism or cells thereof which have been ground, acetone-treated, or lyophilized, capable of asymmetrically reducing the 4-hydroxy-2-butanone into (R)- or (S)-1,3-butanediol.

Abstract: Optically active 1,3-BUTANEDIOL is produced by contacting microorganisms selected from respective groups of specific genuses having an effect of acting on an enantiomeric mixture of 1,3-butanediols and leaving (R)-1,3-butanediol or (S)-1,3-butanediol in enantiomeric mixture, and collecting the remaining optically active (R)-1,3-butandiol or (S)-1,3-butanediol. Optically active 1,3-butanediol can be produced by an economically excellent and convenient means.

Abstract: Optically active 2-hydroxy-4-phenyl-3-butenoic acid can be obtained by treating 2-oxo-4-phenyl-3-butenoic acid with an optionally treated microorganism capable of asymmetrically reducing the 2-oxo-4-phenyl-3-butenoic acid into (R)-2-hydroxy-4-phenyl-3-butenoic acid or (S)-2-hydroxy-4-phenyl-3-butenoic acid to thereby asymmetrically reduce the same into (R)-2-hydroxy-4-phenyl-3-butenoic acid or (S)-2-hydroxy-4-phenyl-3-butenoic acid.

Abstract: 2-Oxo-4-phenylbutyric acid is treated with a microorganism, which has been optionally treated, capable of asymmetrically reducing 2-oxo-4-phenylbutyric acid into either (R)-2-hydroxy-4-phenylbutyric acid or (S)-2-hydroxy-4-phenylbutyric acid, and the (R)-2-hydroxy-4-phenylbutyric acid or (S)-2-hydroxy-4-phenylbutyric acid thus produced is recovered to thereby give optically active 2-hydroxy-4-phenylbutyric acid.The optically active 2-hydroxy-4-phenylbutyric acid is an important intermediate in the synthesis of various drugs such as a remedy for hypertension.

Abstract: An optically active 1,3-butanediol can be produced by either (1) treating a mixture of 1,3-butanediol enantiomers with a microorganism, which has been optionally treated, capable of asymmetrically assimilating said mixture, or (2) preparing a microorganism, which has been optionally treated, capable of asymmetrically reducing 4-hydroxy-2-butanone, and collecting optically active 1,3-butanediol.

Abstract: Optically active 2-hydroxy-4-phenyl-3-butenoic acid can be obtained by treating 2-oxo-4-phenyl-3-butenoic acid with an optionally treated microorganism capable of asymmetrically reducing the 2-oxo-4-phenyl-3-butenoic acid into (R)-2-hydroxy-4-phenyl-3-butenoic acid or (S)-2-hydroxy-4-phenyl-3-butenoic acid to thereby asymmetrically reduce the same into (R)-2-hydroxy-4-phenyl-3-butenoic acid or (S)-2-hydroxy-4-phenyl-3-butenoic acid.

Abstract: Riboflavin is effectively obtained by culturing in a medium (1) a purine-requiring revertant derived from a riboflavin-producing yeast which belongs to the genus Saccharomyces and has a purine requirement or (2) a riboflavin-producing yeast which belongs to the genus Saccharomyces and is resistant to ammonium ion, and collecting the produced riboflavin.

Abstract: Riboflavin is obtained directly from the culture in a high yield by cultivating a riboflavin-producing microorganism in a medium using a lower (C.sub.1 to C.sub.4) aliphatic compound, separating riboflavin contained in the culture in the form of heated aqueous solution from solid matters, and crystallizing riboflavin from the heated aqueous solution.Riboflavin is also prepared in a high yield by cultivating a riboflavin-producing yeast belonging to the genus Saccharomyces which has purine requirements and/or resistance to 3-amino-1,2,4-triazole in a medium and collecting riboflavin formed and accumulated in the medium.Moreover, riboflavin is prepared in a high yield even in the presence of iron ions by preliminarily cultivating in liquid a riboflavin-producing yeast belonging to the genus Saccharomyces and then cultivating it in a riboflavin-producing medium containing zinc ions.