| 摘要 |
PURPOSE:To produce highly pure L-threonine on an industrial scale with simplified purification process suppressing the by-production of alanine and/or valine, by culturing a microbial strain belonging to Providencia genus and having specific properties and activity in a medium. CONSTITUTION:Providencia rettgeri TP3-105 strain which is a mother strain capable of producing L-threonine is subjected e.g. to ultraviolet treatment, etc., to obtain a mutant strain Providencia rettgeri FPSS25 having a pyruvate kinase (EC27.1.40) activity corresponding to <=70% of that of the mother strain. The mutant is cultured aerobically in a medium containing carbon source, nitrogen source, inorganic ion and minor organic component at 5-9 pH and 24-37 deg.C for 48-120hr to produce and accumulate L-threonine in the culture liquid. The liquid is filtered and the filtrate is adjusted to 2 pH, passed through a strongly acidic cation exchange resin, subjected successively to adsorption, elution, concentration and purification procedures and crystallized to obtain the objective compound. |
