| 摘要 |
PURPOSE:To obtain L-threonine useful for a medicine, feed additive, etc., in high accumulating concentration and yield at a low cost, by cultivating a microorganism being L-homoserine resistant strain belonging to the genus Escherichia and having L-threonine producing ability in a culture medium. CONSTITUTION:Escherichia coli ATCC 21248 strain is subjected to variation treatment by ultraviolet ray irradiation, etc., to provide Escherichia coli EH-92 (FERM P-9191) strain being L-homoserine resistant strain exhibiting >=50% growth rate compared with case of cultivation in a medium free from homoserine in growth degree after 24hr when cultivated in a medium added so as to afford 0.2g/l L-homoserine and having L-threonine producing ability. The variant strain is aerobically cultivated in a culture medium containing 2-15wt.% glucose, 0.5-4wt.% urea, 0.001-0.4wt.% valine and 0-4wt.% hepton at 5-9pH and 24-37 deg.C for 48-120hr. Then the filtrate obtained by removing a bacterium cell from the resultant culture medium is adjusted to about pH2 and purified with an ion exchange resin, etc., to provide the aimed L-threonine. |
