Alanine production

Enzymatic Process. Chemically synthesized substrates can be converted to the corresponding amino acids by the catalytic action of an enzyme or the microbial cells as an enzyme source, t - Alanine production from L-aspartic acid, L-aspartic acid production from fumaric acid, L-cysteine production from DL-2-aminothiazoline-4-catboxyhc acid, D-phenylglycine (and D-/> -hydtoxyphenylglycine) production from DL-phenyUiydantoin (and DL-/)-hydroxyphenylhydantoin), and L-tryptophan production from indole and DL-serine have been in operation as commercial processes. Some of the other processes shown in Table 10 are at a technical level high enough to be useful for commercial production (24). Representative chemical reactions used ia the enzymatic process are shown ia Figure 6. 

The ability of peptides CBPOl-GBP 18 to modulate pyridoxamine-mediated transamination was determined by the conversion of pyruvic acid to alanine in both the absence and presence of copper(II) ion, which would be coordinated by the transamination intermediates [32]. In the absence of copper(II) ion,peptide CBP13 showed up to a 5.6-fold increase in alanine production relative to a pyridoxamine model compound and peptide CBP14 produced alanine with a 27% ee of the 1-enantiomer. In the presence of copper(II) ion, peptide CBP13 again showed the greatest increase in product production, with a 31.7-fold increase in alanine production relative to the pyridoxamine model compound. Peptide CBPIO showed optical induction for D-alanine with a 37% ee. 

Most of the amino acids are consumed by insect cells, with the exception of alanine which is produced however, it has been reported that alanine overflow metabolism is energetically wasteful as it is with mammalian cells [63]. The alanine production by insect cells has been interpreted as a strategy to avoid the accumulation of toxic ammonia produced from amino acid catabolism [64]. 

Also Tanabe have extended the use of that aspartic acid producing process by using the L-aspartic acid as the substrate for L-alanine production using P. dacunae cells with L-aspartate decarboxylase activity. This process has been operating since 1982 using sequential colunms of iimnobihsed E. coli and P. dacunae cells (Chibata, Tosa and Takamatsu, 1987). Also, DL-aspartic acid can be used as the feed in this process. Then, D-aspartic acid is obtained as an additional product, for which there is a modest demand. 

D-alanine production by alanine racemase, and then preferential excretion of the D-alanine across the cell membrane into the medium. 

Chibata, I., Tosa, T. and Takamatsn, S. (1987) Continuous L-alanine production using two different iimnobilized cell preparations on an industrial scale. Methods in Enzymology, 136, 472-478. 

An example of coenzyme regeneration with isolated enzymes is L-alanine production from pyruvate with an NADH-dependent alanine dehydrogenase (AlaDH) ... 

Figure 10.7 L-Alanine production from DL-lactate via pyruvate with cofactor regeneration (Wandrey, 1984).

The strains used are either wild types or mutants. Wild types from the genera Arthrobacter, Bacillus, Brevibacterium, Corynebacterium and Microbacterium are mostly employed in glutamic acid and alanine production 48). The yields, depending on the carbon source and bacterial species, are between 10-80%. Other amino acids are also accumulated in wild types however, yields are lower. 

Fig. 7.3. Alanine production with cofactor regeneration. The black and gray dumbbell shapes are the reduced and oxidized forms of the NAD cofactor bound to polyethylene glycol.

COMPARISON OF EFFICIENCIES AND STABILITIES OF CONVENTIONAL AND CLOSED COLUMN REACTORS FOR L-ALANINE PRODUCTION... 

Therefore one speaks of a glucose alanine cycle involving the conversion of alanine to pyruvate through the catalytic action of the proper transaminase. If starvation is prolonged, the alanine production in muscle is reduced and gluconeogenesis decreases in spite of the fact that the activities of the liver enzyme remain adequate. 

It is known to occur in CAM plants and has been implicated in alanine production during CAM by Queiroz et al. (1972). 

L-Alanine production by fermentation is difficult because bacteria usually have an alanine racemase to racemize the product. Fermentative production of L-alanine with racemase-defident strains of Corynebacterium glutamicum, Brevibacterium flavum, and Arthrobacter oxydans (Hashimoto and Katsumata 1999) has been investigated, and good yields have been reported, although the method is not yet industrially applicable. 

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