Nh

H2SO4

Beckman's transposition DL-Aminocaprolactam reacti°n

(b) Enzymatic reaction D-Aminocaprolactam

Achromobacter obae (Racemase)

L-Aminocaprolactum

Cryptococcus laurentii (Hydroxylase)

L-Lysine

Figure 3. l-Lysine production by a combination of synthetic and enzymatic reactions. Source: Ref. 8.

Wild-Type Strains

Microorganisms suitable for the purpose are selected from nature. They are cultured under adjusted fermentation conditions so as to produce excess amounts of the desired products. Typical examples are C. glutamicum and Brevi-bacterium flavum used for L-glutamic acid fermentation.

Mutant Strains

Auxotrophic strains and amino acid analog-resistant strains fall into the mutant strain category. Most amino acids can be produced by these types of microorganisms. Currently, most fermentative production of amino acids is accomplished in this fashion. Tables 3 and 4 and Figure 4 show L-lysine producers and L-tryptophan producers as typical examples of strain improvement.

Table 3. L-Lysine-Producing Microorganisms l-Lysine HCl productivities

Microorganismsa

aAEC, S-(2-aminoethyl)-L-cysteine; Pant, pantothenate.

Conc.

Yield

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