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ABSTRACT:
Poly-ß-hydroxybutyrate (PHB) is a representative member of polyhydroxyalkanoates (PHAs) formed in
many bacteria as a carbon and energy reserves under unbalanced (unfavourable) growth conditions,
such as nutrient limitation (Wang and Yu, 2000). PHB and other PHAs have attracted attention as the
candidates for biodegradable polymers, because they posses the similar material properties of the
common petrochemical-based synthetic thermoplastics and elastomers currently in use (Haywood et al.,
1990). PHB are considered to be strong candidates for biodegradable polymer material because they
currently in use (from polypropylene to synthetic rubber) and, upon disposal, they are completely
degraded to water and carbon dioxide (and methane under anaerobic conditions) by microorganisms in
various environments such as soil, sea and lake water and sewage (Mergaert et al., 1992; Brandl et al.,
1995). PHB also has been reported from several researchers to be the more common storage polymer
under conditions of carbon sources excess (van den Eynde et al., 1984; Smolders et al., 1995; Van Aalstvan Leeuwen, M.A. et al., 1997). Since then, extensive studies have been conducted on PHB production
in batch or fed-batch operation for feasibility studies, high cell density cultivation and high polymer
content (Kim et al., 1994; Tanaka and Ishizaki, 1994).