Polyhydroxyalkanoates: From Bacterial Storage Compound via Alternative Plastic to Bio-bead
Katrin Grage, Verena Peters, Rajasekaran Palanisamy and Bernd H. A. Rehm
from: Microbial Production of Biopolymers and Polymer Precursors: Applications and Perspectives (Edited by: Bernd H. A. Rehm). Caister Academic Press, U.K. (2009)
Polyhydroxyalkanoates (PHAs) are organic polyesters composed of (R)-3-hydroxy fatty acids which are synthesized by most bacteria as a carbon and energy storage material in times of unbalanced nutrient availability. They are deposited intracellularly as insoluble spherical inclusions called PHA granules which consist of a polyester core surrounded by a phospholipid layer with attached proteins. One of these proteins is the PHA synthase, the key enzyme of PHA biosynthesis, which catalyzes polyester formation from different (R)-3-hydroxyacyl-CoA precursors. The PHA synthase remains covalently attached to the polyester and thus to the PHA granule; other granule-associated proteins are involved in depolymerization, regulation or structural stabilization. This chapter provides a comprehensive overview of the current understanding of PHAs and PHA granules, including granule biogenesis and granule-associated proteins. In recent years, apart from investigating in particular the granule self-assembly process and the function of granule-associated proteins, a lot of research interest has been focused on the usability of this natural system. Accordingly, this review will also give an overview of metabolic engineering and large-scale production approaches, and discuss applications of PHAs as biocompatible and biodegradable plastics as well as the potential applicability of PHA granules as micro- / nano-beads read more ...