Abstract: L-phenylalanine is produced by using a microorganism belonging to the species Citrobacter freundii, Erwinia herbicola, Enterobacter cloacae, Klebsiella oxytoca, Salmonella typhimurium, Bacillus cereus, Flavobacterium suaveolens, Serratia marcescens, Pseudomonas putida, Enterobacter cloacae, Proteus mirabilis, Paracoccus denitrificans, Arthrobacter globiformis, Bacillus sphaericus, Corynebacterium hydrocarboclastus, Kluyvera micum or Microbacterium ammoniaphilum and having the ability to convert phenylpyruvic acid into L-phenylalanine in the presence of an amino group donor; or fumaric acid and ammonium ion or urea.

Abstract: L-histidine is produced by culturing, in a nutrient medium, an L-histidine producing mutant microorganism belonging to the genus Corynebacterium or Brevibacterium. The mutant is resistant to growth inhibition by an RNA polymerase inhibitor or requires adenine. L-histidine is accumulated in the culture liquor and is recovered therefrom.

Abstract: A process for converting glycine to L-serine is effected by the use of an aqueous medium containing glycine and microbial cells of a mutant belonging to the genus Nocardia. The mutant is capable of converting glycine to L-serine and has no or lowered ability to decompose L-serine and/or a resistance to at least one metabolic antagonist selected from those of glycine, serine, methionine, glutamine, histidine, leucine, isoleucine, valine, purine, pyrimidine or folic acid. The L-serine is accumulated in the aqueous medium and is recovered therefrom.

Abstract: A process for producing L-lysine by fermentation includes the steps of culturing a strain belonging to the genus Corynebacterium having both an ability to produce L-lysine and a resistance to at least one member selected from the group consisting of aspartic acid analogs and sulfa drugs in a nutrient medium, forming and accumulating L-lysine in the resulting culture liquor and thereafter recovering the L-lysine therefrom.

Abstract: L-arginine is produced by fermentation of a microorganism belonging to the genus Bacillus capable of producing L-arginine and having a nutritional requirement for at least one compound of the group consisting of methionine, histidine, threonine, proline, isoleucine, lysine, adenine, guanine and uracil or its precursor. L-arginine is accumulated in the culture liquor and may be recovered therefrom.