Abstract: Fumaric acid is produced by reacting a culture of a microorganism which produces maleate isomerase that exhibits a maximum activity at not less than 50.degree. C. or a treated product thereof with maleic acid in an aqueous solution, and isomerizing maleic acid to produce fumaric acid. L-aspartic acid is produced by reacting both of a culture of a microorganism which produces maleate isomerase or a treated product thereof and a culture of a microorganism which produces aspartase or a treated product thereof with maleic acid and ammonia in an aqueous solution, producing L-aspartic acid from maleic acid and ammonia by enzyme reactions, and recovering L-aspartic acid from the reaction mixture.

Abstract: There is disclosed a process for preparing indigo which comprises bringing an indigo-producing bacteria belonging to genus Acinetobacter or treated products thereof into contact with an aqueous solution containing at least indole to have indigo formed and accumulated in the aqueous solution; and collecting indigo from the aqueous solution.

Abstract: A method for producing L-threonine, which comprises subjecting at least L- or DL-aspartic acid or a salt thereof to enzymatic reaction according to the reaction system not accompanied with growth of microorganism cells in an aqueous solution in the presence of a microorganism and collecting L-threonine formed, wherein the microorganism is a biotin-requiring microorganism for the growth belonging to coryneform bacterium; a plasmid comprising a DNA fragment containing at least a gene encoding biosynthesis of threonine which can be expressed within a biotin-requiring microorganism cell for the growth belonging to coryneform bacterium and a DNA fragment containing a gene encoding autonomous replication within coryneform bacterium cell; and a biotin-requiring microorganism for the growth belonging to coryneform bacterium which has been transformed with the plasmid described above, both of which are employed in the present method.

Abstract: Microorganisms of the genus Pseudomonas containing aspartate beta-decarboxylase at a high level are produced by culturing said microorganism in a medium supplemented with a chelating agent. L-Alanine can be efficiently produced from L-aspartic acid said microorganisms or the treated product thereof.

Abstract: There is disclosed a process for producing L-alanine by reacting in a single reaction tank, in an aqueous reaction mixture having a pH of 6 to 10 and containing at least one .alpha.-keto acid, fumaric acid or a salt thereof with ammonia or ammonium ions in the presence of two microorganisms having fumarase inactivity.

Abstract: An aqueous solution containing fumaric acid is reacted in the presence of an aerobically cultured product of a microorganism belonging to the Brevibacterium genus and having resistance to .alpha.-aminobutyric acid, whereby L-malic acid is produced.

Abstract: L-threonine is produced by aerobically culturing a bacterium belonging to the genus Acinetobacter, which utilizes ethanol and has an ability to produce and accumulate L-threonine, in a culture medium in which ethanol is the main carbon source to produce and accumulate L-threonine in a culture liquor and recovering L-threonine from the culture liquor. The bacterium is preferably a mutant of Acinetobacter calcoaceticus YK-1011 (Ferm-P No. 5910).

Abstract: A process for producing L-aspartic acid economically and efficiently from fumaric acid or a salt thereof and ammonia or an ammonium salt using a cultured product obtained by aerobically culturing an microorganism belonging to the Genus Brevibacterium and having resistance to .alpha.-amino-n-butyric acid.

Abstract: A process for producing L-valine or L-lysine which comprises aerobically culturing a bacterium belonging to the genus Acinetobacter, which utilizes ethanol and has an ability to produce and accumulate L-valine or L-lysine, in a culture medium in which ethanol is the main carbon source to produce and accumulate L-valine and/or L-lysine and collecting.