Industrial Biotransformations

l-Phenylalanine ammonia-lyase
Rhodotorula rubra
1 = trans-cinnamic acid
2 = ammonia
3 = L-phenylalanine
Fig. 4.3.1.5 – 1
1) Reaction conditions
[1]: 0.088 M, 13.02 g · L –1 [148.16 g · mol –1 ]
[2]: 9.307 M, 158.5 g · L –1 [17.03 g · mol –1 ]
[3]: 0.258 M, 42.7 g · L –1 [165.19 g · mol –1 ]
pH: 10.6
T: 25 °C
medium: aqueous
reaction type: C-N bond formation
catalyst: suspended whole cells
enzyme: l-phenylalanine ammonia-lyase (PAL, l-phenylalanine deaminase, tyrase)
strain: Rhodococcus rubra (Genex 1983), Rhodotorula rubra (Genex 1986), wild type
CAS (enzyme): [9024–28–6]
2) Remarks
1
COOH COOH
+ NH 3
● The PAL-producing microorganisms are initially cultivated under aerobic, growth-promoting
conditions.
● Due to the instability of the enzyme towards oxygen, the biotransformation is performed
under anaerobic, static conditions.
● An aqueous solution of trans-cinnamic acid is mixed with 29 % aqueous ammonia and the pH
is adjusted by addition of carbon dioxide.
● As biocatalyst 5.88 g · L –1 (dry weight) Rhodotorula rubra cells are added.
EC 4.3.1.5
Genex Corporation
● The reaction is performed in fed batch mode with periodic addition of concentrated ammonium
cinnamate solution.
● The enzyme is deactivated by oxygen and by agitation. Therefore the reaction medium is
sparged with nitrogen before the addition of the cells. Instead of stirring, the bioreactor contents
are mixed after each addition of substrate solution by sparging with nitrogen.
● Instead of starting from trans-cinnamic acid, the fermentation process now starts from glucose.
The yields of this de novo process are high and up to 25 g · L –1 of l-phenylalanine are
obtained.
502
E
2 3
NH2