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acids, from formate to decanoate, as the sole carbon sources. Formation of
intracellular poly(b-hydroxyalkanoates) was observed for hexanoate and the
higher n-alkanoic acids. In most cases, the major repeating unit in the
polymer had the same chain length as the n-alkanoic acid used for growth,
but units with two carbon atoms fewer or more than the acid used as a
carbon source were also generally present in the polyesters formed. Co-
polymers containing as many as six different types of b-hydroxyalkanoate
units were formed.
75
P. oleovorans was also used to produce methyl-
branched PHA such as poly(3-hydroxy-6-methylnonanoate), P(H6MN), when
grown on mixtures of methyloctanoates with n-octanoate. The polyesters
obtained from 7-methyloctanoate and from its mixtures with n-octanoate
contained units with the methyl branches in the pendant group, as did the
copolymers from mixtures of 5- and 6-methyloctanoate with n-octanoate.
The average molecular weights of the copolyesters produced were in the
range of 220 000 to 410 000, with Mw/Mn ratios of 1.7 to 1.9.
76
Choi and Yoon (1994) tested forty-two different carbon sources for poly-
ester synthesis by Pseudomonas citronellolis (ATCC 13674). These included
linear C
2
to C
10
monocarboxylic acids, C
3
to C
10
dicarboxylic acids,
saccharides, a,
$
-diols, hydrocarbons, and 3-methyl-branched substrates
such as 3,7-dimethyl-6-octen-1-ol (citronellol), 3-methyl-n-valerate, 3-methyl-
1butanol, and 3-methyladipate.
77
Polyesters from nine monocarboxylic acids
and two related carbon sources could be metabolically divided into three
groups. The first group of C
2
to C
4
carbon sources resulted in copolyesters
composed of 61 to 70 mol% 3-hydroxydecanoate, 23 to 33 mol%
3-hydroxyoctanoate, 3.6 to 9.0 mol% 3-hydroxy-5-cis-dodecenoate, and 1.8 to
2.6 mol% 3-hydroxy-7-cis-tetradecenoate. Carbon sources in group II (C
7
to
C
10
) produced copolyesters composed of 3-hydroxyacid monomer units with
the same number of carbon atoms as the substrate (major constituent) and
monomer units with either two fewer or two more carbons. Negligible
amounts of 3-hydroxy-5-cis-dodecenoate and 3-hydroxy-7-cis-tetradecenoate
were detected in copolyesters from this group. Copolyesters from group III
(C
5
and C
6
) had a monomer unit distribution that could be said to be
between those of groups I and II. In addition, a novel copolyester, poly(3-
hydroxy-7-methyl-6-octenoate-co-3-hydroxy-5-methylhexanoate), was
d
n
2
r
4
n
g
|
8
.
syn-
thesized when grown on citronellol.
55
A number of Pseudomonas strains can accumulate PHAs from a variety of
aromatic hydrocarbons. In many strains, the level of PHA accumulation is
dependent on the side chain length of the phenylalkanoic acid provided for
growth.
78
The PHA accumulated from styrene and phenylacetic acid was
composed of aliphatic monomers only. The PHA accumulated from any one
of the phenylalkanoic acids with five carbons or more in their side chain was
almost identical for all strains with the PHA composed of both aromatic and
aliphatic monomers. The predominant monomers accumulated were
3-hydroxyphenylvaleric acid and 3-hydroxyphenylhexanoic acid. The add-
ition of the metabolic pathway inhibitors acrylic acid and 2-bromooctanoic
acid resulted in decreased levels of PHA from phenylacetic acid, suggesting a
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