AbstractThe present work describes an approach that uses a reduction in biomass accumulation during fermentation to improve the properties of a strain producing L-threonine. Glutamyl- and glutaminyl-tRNA synthetases were chosen as targets. Mutants carrying temperature-sensitive alleles of the mentioned enzymes were obtained. It was shown with this system that suppression of the function of tRNA synthetases led to the rapid arrest of culture growth and an increase in the productivity and conversion of L-threonine synthesis. One of the temperature-sensitive strains was used to obtain mutants with the ts phenotype under nonpermissive conditions. Some of these mutants accumulated less biomass and produced 10–12% more threonine than the original strain.