Molecular breeding of a Brevibacterium lactofermentum L-phenylalanine producer using a cloned prephenate dehydratase gene
1990
Ito, H. | Sato, K. | Matsui, K. | Sano, K. | Enei, H. | Hirose, Y.
The prephenate dehydratase gene was cloned from a mutant of Brevibacterium lactofermentum, AJ11957 that produced enzyme free from feedback inhibition. The recombinant plasmids pPH11 and pPH14 complemented a phenylalanine auxotroph of B. lactofermentum, A-15, provided the transformant with the desensitized enzyme and caused an increased level of the enzyme compared to that of a wild strain. Plasmid pPH14 was introduced into L-phenylalanine producers genetically induced from B. lactofermentum; MF358 and FP-1 excreting L-tyrosine and anthranilate, respectively, as by-products. Both transformants predominantly accumulated L-phenylalanine at the expense of by-product formation. Co-existence of pPH14 and pTAR16, a recombinant plasmid expressing desensitized 3-deoxy-D-arabino-hepturosonate-7-phosphate synthase had a marked effect on further improvement in L-phenylalanine productivity, accompanied by an increase in the corresponding enzyme activity. The parent, MF358, accumulating 5.5 g/l L-phenylalanine, 6.8 g/l L-tyrosine and 0.3 g/l anthranilate turned into a potent L-phenylalanine producer producing 18.2 g/l L-phenylalanine and 1.0 g/l L-tyrosine by-product.
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