Auxotrophic Mutant Strains

Many kinds of amino acids are accumulated by auxotrophic strains that mutated to require a growth factor. l-Lysine is produced by a homoserine auxotrophic mutant of glutamic acid-producing bacteria; B. lactofermentum and Corynebacterium glutamicum and typical examples. In glutamic acid bacteria, l-lysine is formed by way of the branched pathway shown in Figure 3. The aspartate kinase, which is the first key enzyme of lysine biosynthesis, is inhibited by the combination of l-threonine and l-lysine, and l-lysine is among the amino acids not overproduced. In the homoserine auxotroph, if the supply of l-threonine is limited, l-lysine formed by de novo synthesis does not inhibit the first enzyme without the aid of l-threonine. In this mutant, the metabolic flux is genetically blocked to flow in the direction of threonine and methionine biosynthesis. This is one of the main reasons for the overproduction of l-lysine in mutant strains (38).

Anti-Aging Report

Anti-Aging Report

When people generally think about anti-aging, they tend to think about the visible signs of wear and tear, those tell-tale wrinkles, age spots and their developing jowls. No-one wants to get old, let alone feel and look older than their years and anti-aging treatments are becoming so sought after by both men and women that the skincare market is colossal, but what really works?

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