L-PHENYLALANINE PRODUCTION BY DOUBLE AUXOTROPHIC ANALOG RESISTANT MUTANTS OF ARTHROBACTER-GLOBIFORMIS

A number of tryptophan plus tyrosine double auxotrophic mutants isolat ed by the NTG treatment of a glutamate producing strain of Arthrobacte r globiformis were found to excrete phenylalanine in a mineral salt me dium. By controlling the pH of the medium to near neutrality, the acti ve growth period could be extended up to 72 h and more phenylalanine w as accumulated compared to the unregulated culture where the growth pe riod took up to 48 h. Under optimum culture conditions, the best doubl e auxotroph (TT-39) produced 3 g phenylalanine/l. Further improvement of phenylalanine production has been achieved by the step-by-step isol ation of a mutant resistant to the phenylalanine analogues p-fluorophe nylalanine (PFP) and beta-2-thienylalanine (TA) from the TT-39 strain. Under optimum culture conditions, the best double auxotrophic analogu e resistant mutant TT-39 PT(r)-21 yielded 8.7 g/l phenylalanine.