Usually, scl-PHAs, especially PHB, constitute highly
crystalline materials, although they are amorphous within
the bacterial cell. The crystallization rapidly occurs after
disruption of cells when the polymer is extracted. A com-
mon Xc is typically found between 60 and 80%, the Tg
about 4°C and the Tm about 160–180°C (Sudesh et al.
2000; Khanna and Srivastava 2005; Valappil et al. 2007).
In this study, the three PHB samples extracted from
B. megaterium uyuni S29 showed very different thermal
properties compared with the usual PHAs. The biopolyest-
ers extracted from both fed-batch experiments (bioreactor
and shaking flasks) showed lower thermal parameters
compared with the common ones from PHBs. These
results coincide with the thermal properties of the bio-
polymer extracted in initial studies with this strain
(Rodr ıguez-Contreras et al. 2013). Particularly, the
extracts from the bioreactor experiment showed even
lower Xc and Tg (Table 2). The obtained thermal values
confirmed that different fermentation processes and
extraction techniques can influence the thermal properties,
corresponding to the findings reported by Valappil et al.
(2007). Low thermal properties shown by the chloroform
extraction technique could be explained by the presence of
possible impurities. The method may allow lipids, fatty
acids and other hydrophobic cellular materials to be
extracted along with PHB. However, the fact that the
polymer extracted via Soxhlet-acetone also showed low
thermal properties confirms that this is a property of the
biopolymer synthesized by B. megaterium uyuni S29.
Usually, scl-PHAs, especially PHB, constitute highly
crystalline materials, although they are amorphous within
the bacterial cell. The crystallization rapidly occurs after
disruption of cells when the polymer is extracted. A com-
mon Xc is typically found between 60 and 80%, the Tg
about 4°C and the Tm about 160–180°C (Sudesh et al.
2000; Khanna and Srivastava 2005; Valappil et al. 2007).
In this study, the three PHB samples extracted from
B. megaterium uyuni S29 showed very different thermal
properties compared with the usual PHAs. The biopolyest-
ers extracted from both fed-batch experiments (bioreactor
and shaking flasks) showed lower thermal parameters
compared with the common ones from PHBs. These
results coincide with the thermal properties of the bio-
polymer extracted in initial studies with this strain
(Rodr ıguez-Contreras et al. 2013). Particularly, the
extracts from the bioreactor experiment showed even
lower Xc and Tg (Table 2). The obtained thermal values
confirmed that different fermentation processes and
extraction techniques can influence the thermal properties,
corresponding to the findings reported by Valappil et al.
(2007). Low thermal properties shown by the chloroform
extraction technique could be explained by the presence of
possible impurities. The method may allow lipids, fatty
acids and other hydrophobic cellular materials to be
extracted along with PHB. However, the fact that the
polymer extracted via Soxhlet-acetone also showed low
thermal properties confirms that this is a property of the
biopolymer synthesized by B. megaterium uyuni S29.
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