抄録
1. One acetate kinase-negative, 53 phosphate acetyltransferase-negative, and seven isocitrate lyase-negative strains were found among 73 mutants of Brevibacterium flavum, which grew on glucose but not on acetate. The result indicates that these enzymes are essential for the utilization of acetate in B. flavum, and also that the participation of acetyl-CoA synthetase is absent in this strain.
2. The genetic defect of any one of these three enzymes had no effect on the production of L-glutamate from glucose.
3. Many mutants possessing a variety of isocitrate lyase activities were obtained by deriving revertants grown on acetate from four isocitrate lyase-negative strains. By an experiment using such revertants, it was concluded that isocitrate lyase had an important effect on the production of L-glutamate from acetate, which was shown as a positive correlation between the activity of this enzyme and L-glutamate productivity in the cells grown in an acetate medium. It was also shown that the change of this enzyme activity had no effect on the production of L-glutamate from glucose.
4. Mutants possessing a variety of phosphate acetyltransferase activities were obtained by deriving revertants grown on acetate from four strains lacking this enzyme. In this case, too, a positive correlation was observed between the activity of this enzyme and L-glutamate productivity in the cells grown in an acetate medium.
5. In connection with the present study, it was pointed out that genetic elevation of the levels of key enzymes was important for the improvement of microbial strains for industrial purposes.
