Chemistry Reference
In-Depth Information
acid has been projected to have the lowest cost in
comparison with other routes currently being used
industrially.
Both 1,2-propanediol and 1,3-propanediol can
be derived from the common biological intermediate
dihydroxyacetone phosphate, a product of sugar
metabolism. Over 4.5 ¥ 10
5
t of 1,2-propanediol
(propylene glycol) currently is produced from
propene. Cameron has developed a biochemical
process for the production of 1,2-propanediol from
glucose by engineering a new metabolic path in
E.
coli
[132]. 1,2-Propanediol is a particularly interest-
ing target for green process technology because
commercial production proceeds by hydration of
propylene oxide, derived from the corresponding
chlorohydrin or via a hydroperoxide [133]. Both
commercial routes generate waste salt.
1,3-Propanediol is being developed as a compon-
ent of new polyesters, specifically, poly(propylene
terephthalate). The market for this material is begin-
ning to develop with DuPont and Genencor's
announced intent to make a polymer based on 1,3-
propanediol commercially [134]. This material
would be related to other polyesters such as
poly(butylene terephthalate), from 1,4-butanediol,
and poly(ethylene terephthalate), from ethylene
glycol. The resulting polyester family could have a
broad range of uses because variation of chain length
in the diol component of polyesters imparts unique
properties to the resulting polymer [135]. The
current bioprocessing route uses glycerol as a start-
ing material, which is relatively expensive, thus
recent work on 1,3-propanediol production has been
directed at sugar fermentation. Interest in biodiesel
also could reduce the price of glycerol. Production of
10 kg of biodiesel gives 1 kg of glycerol as a by-
product that could be used for lower cost production
of 1,3-propanediol [136].
Frost has reported several biochemical transfor-
mations that could be useful in the future for com-
modity chemical manufacture (Fig. 14.9). A new
approach to adipic acid eliminates all toxic, non-
renewable components by replacing them with an
elegant biosynthetic pathway. Starting from glucose,
adipic acid was produced by an engineered
E. coli
organism via
cis
,
cis-
muconic acid as an intermediate
[137]. Additional research has revealed routes to
catechol [138] and vanillin [139]. These transforma-
tions provide another example of reaction control
through understanding of mechanism. The different
biochemical paths by which glucose is metabolised
are well characterised. Hence, the product distribu-
tion could be changed by altering the mechanism
towards production of the materials of interest.
As with non-biological catalysis, bioprocessing has
found utility in the production of the more active
optically pure forms of ibuprofen and naproxen.
.The conventional biochemical approach uses kinetic
resolution via asymmetric enzymatic hydrolysis of
precursor esters in an aqueous system [140]. Other
organisms have been studied for hydrolysis of the
racemic acid or amide derivative [141]. For highest
Fig. 14.9
Biochemical transformations
of glucose to industrial chemicals.
