Industrial Biotransformations

Lactate dehydrogenase
Staphylococcus epidermidis
Alternatively immobilized whole cells of Proteus vulgaris can be used in a fixed bed reactor:
● By using small units of biomass in the form of a packed bed of immobilized cells, high amounts
of the hydroxy acid can be produced. The space-time-yield is high and the costs for down-stream
processing are low (conversion > 99.5 %; ee = 99.8 %; space-time yield = 180 g · L –1 ·d –1 ; enzyme
consumption= 159 U · kg –1 ).
● Per liter of fermentation broth 1.45 g cell mass (80 wt.-% water) can be isolated.
● The emulsion of cells, chitosan and solid silica is dropped into a polyphosphate solution resulting
in ionotropic gel-beads.
● 1,000 g cell emulsion yields 400 g (= 800 mL) beads. The beads contain 0.25 g (wet cells) · g –1
(beads).
● Here electron mediators (= V) are used instead of NADH or NADPH:
Fig. 1.1.1.28 – 2
2 Cl -
+
+
N N
+
+
N N
● The enzymes in the cells are capable of reducing and oxidizing the mediators. In this case the
carbamoylmethylviologen is used. The following figure shows the regeneration cycle:
● To avoid degassing of CO 2 the reaction is carried out under a pressure of 3 bar.
O
NH 2
2 Cl -
H2N
benzyl viologen carbamoyl methyl viologen
1
COOH
1 = 2-oxo-4-phenyl-butyric acid (OPBA)
2 = 2-hydroxy-4-phenyl-butyric acid (2-HPBA)
Fig. 1.1.1.28 – 3
O
H 2O + CO 2
D-lactate-dehydrogenase
2 H + + 2V + 2 V ++
formate dehydrogenase (FDH)
HCOOH
OH
(R)-2
EC 1.1.1.28
O
COOH
177