[Effect of the carbon source and aeration conditions on homoserine lysine biosynthesis in the threonine-dependent mutant Brevibacterium flavum 2T].

The effect of two carbon sources (sucrose and acetate), aeration conditions and threonine concentration on the homoserine and lysine biosynthesis by the threonine-dependent mutant Brevibacterium flavum 2T was examined. It was demonstrated that acetate provided the predominant synthesis of homoserine to a far greater extent than sucrose (with the weight/weight ratio of homoserine : lysine being 2.5-5.0 and 0.8-1,2, respectively). The maximal level of homoserine and lysine was 18-21 and 3-7 g/l on the acetate containing medium and 18-22 and 12-16 g/l on the sucrose containing medium, respectively. On sucrose the total amount of amino acids and the total yield of products as related to the consumed substrate were greater than on acetate. Using the sucrose medium, the effect of aeration conditions and threonine concentration on the biosynthesis of both compounds was investigated. With an aeration increase from 1.3 to 4.6 g O2/l.hr the optimal concentration of threonine in the medium grow. The biosynthesis of homoserine was less sensitive to the inhibitory effect of excessive threonine than that of lysine. With an increase of the threonine concentration in the medium from 0.25 to 3.0 g/l the ratio homoserine : lysine grew from 1.03 to 5.20 (with the sulphite number being 4.6 g O2/l.hr). This effect was independent of the aeration conditions.