Abstract
Two types of L-isoleucine producing mutants were derived from L-threonine producers by the supplement of the resistance to ethionine.
Main control site in L-isoleucine biosynthetic pathway after threonine is threonine dehydratase. In case of Brevibacterium flavum No. 14083, L-isoleucine production was based on the insensitiveness of this key enzyme to feedback inhibition by L-isoleucine. As regards Brevibacterium flavum No. 168, it was based on the increase in the specific activity of this enzyme.
The former produced 11.3g/liter of L-isoleucine and the latter produced 9.92g/liter from glucose. The former showed a vigorous ability of acetic acid assimilation, but the latter did not.
