oleovolans to produce the polyester since the considerable decreased cell mass and undetectable
amount of polyesters accumulation were observed. In contrast A. eutrophusseemed to grow
well at pH 5, 30°C with aeration condition. Although the result indicated that A. eutrophus grew
well at pH 5 compared to pH 7, in later experiments pH 7 was chosen in order to support the
parallel study that is focused on the biopolyester production from agricultural feedstock using
simultaneous saccharification and fermentation process in which the enzymes involving the
saccharification is optimized at pH 7. Table III represented the types of biopolyesters produced
from varieties of carbon sources from A. eutrophus. P(3HB) homopolymer can be produced from
simple carbon source such as sugar (glucose, fructose), fatty acid (acetic acid, butyriC acid) or
alcohol (methanol, ethanol), whereas the copolymers consisting of 3HB can be synthesized from
either single or co-carbon sources resulting the formation of biopolyester containing 3
hydroxyvalerate [20-21,27-28, 30] or 4-hydroxybutyrate [22-23]. Previous research reported that
when bacteria were cultivated on medium containing only glucose as sole carbon source, true
copolymers are being accumulated rather than blend of homopolymers [31]. It is essential that
the same bacterial cells can uptake different carbon sources at the same time. Nurbas et a/./
(2004) reported that A. eutrophus produced 100% P(3HB) homopolymer when used 2% w/v
glucose as sole carbon source [30]. In general P(3HB) homopolymer is a common product of PHA
production as glucose is used as sole carbon source. However,HV monomer can be synthesized
during the glucose metabolism via the conversion of succinyl CoA to the methylmalonyl-CoA,
which is decarboxylated to propionyl-CoA.