| 摘要 |
PURPOSE:To obtain L-threonine in much high yields, by cultivating a strain having high L-threonine producing power, obtained from a plasmid containing deoxyribonucleic acid carrying genetic information related to the synthesis of L-threonine. CONSTITUTION:A plasmid containing a deoxyribonucleic acid (DNA) fragment carrying genetic information related to the synthesis of L-threonine, obtained from a well-knoun mutant belonging to a genus of Escherichia, having fastness to alpha-amino- beta-hydroxy valeric acid. The recombined plasmid is introduced into bacteria belonging to a genus of Escherichia not requiring L-threonine to give a strain having high L-threonine producing power. The resulting L-thermonine producing strain is cultured in a conventional medium comprising a carbon, nitrogen sources, and inorganic ion, and, if necessary, a trace amount of organic nutrient. The cultivation is carried out under aerpoboic condition with the pH and the temperature of the medium properly regulated until L-threonine stops formation and accumulation. L- threonine is obtained from the cultured liquid by a conventional method. |
