Biocatalysis - Green Chemistry and Technology - page 192

Fig. 9.9 Production of a
podophyllotoxin by Podophyllum
peltatum .

Fig. 9.10 Biocatalytic routes for the formation of vanillin.

extraction has a long history [18,19], but the appli-
cation of biocatalysis—the conversion of a single
substrate to a targeted product—is a more recent
development of the field. In the latter area, a prime
target is the widely used flavour chemical vanillin,
which can be produced from either ferulic acid [20]
or vanillic acid [21] by biocatalysis using a variety of
microbial systems (Fig. 9.10). One of these, the
fungus Pycnoporus cinnabarinus , has been developed
as a biocatalyst for the conversion of vanillic acid
into vanillin at levels of over 1 g l -1

Fig. 9.11 Production of methyl anthranilate using soybean
peroxidase (SBPO).

strain in which the enzymic pathway for degradation
of the production is absent (Fig. 9.12) [23]. This
process has been optimised by the Lonza group and
production levels of over 100 g l -1 are attainable.
Another large-scale application—the production
of the artificial sweetener aspartame—was devel-
oped by the Tosoh Corporation in Japan and uses the
isolated enzyme thermolysin to couple suitably pro-
tected aspartate and phenylalanine precursors (Fig.
9.13) [24]. This process has been optimised to
operate with racemic phenylalanine methyl ester,
the coupling reaction being specific for the natural
( L ) isomer.

under scaleable

conditions [21].
In an application employing an isolated enzyme
biocatalyst methyl anthranilate, an important
topnote flavour agent in Concord grape juice can be
obtained efficiently from N -methyl methyl anthrani-
late by N-demethylation using soybean peroxidase
(SBPO) and hydrogen peroxide (Fig. 9.11). The sub-
strate for this conversion is readily obtainable from
a renewable source (citrus leaves), making the
process an attractive one for the production of the
target compound [22].
The slimming aid and dietary supplement L -
carnitine is produced on a multi-hundred-tonne scale
annually. One route for its preparation is the hydrox-
ylation of g-butyrobetaine using a mutant bacterial

2.4 Carbohydrates

The classic example of carbohydrate production by
biocatalysis is the manufacture of vitamin C (ascor-