Bacterial Polyhydroxyalkanoate Granules: Biogenesis, Structure, and Potential Use as Nano-/Micro-Beads in Biotechnological and Biomedical Applications

Abstract

Polyhydroxyalkanoates (PHAs) are naturally occurring organic polyesters that are of interest for industrial and biomedical applications. These polymers are synthesized by most bacteria in times of unbalanced nutrient availability from a variety of substrates and they are deposited intracellularly as insoluble spherical inclusions or PHA granules. The granules consist of a polyester core, surrounded by a boundary layer with embedded or attached proteins that include the PHA synthase, phasins, depolymerizing enzymes, and regulatory proteins. Apart from ongoing industrial interest in the material PHA, more recently there has also been increasing interest in applications of the PHA granules as nano-/micro-beads after it was conceived that fusions to the granule associated proteins (GAPs) provide a way to immobilize target proteins at the granule surface. This review gives an overview of PHA granules in general, including biogenesis and GAPs, and focuses on their potential use as nano-/micro-beads in biotechnological and biomedical applications.

Bacterial polyhydroxyalkanoates-eco-friendly next generation plastic: Production, biocompatibility, biodegradation, physical properties and applications

“…Both models consider the defined location of the polyester synthase and to some extent the phasin protein on the surface of the granule. The micelle model is certainly supported by PHA granule formation in vitro and in the absence of membranes ( Figure 3) (45,117). However, electron microscopy studies showing membrane-like material surrounding PHA granules in intact cells (118) or isolated granules (119) provided evidence for the budding model.…”

“…Whereas P. oleovorans is estimated to have about one or two large granules (128). The PHA granules are mostly spherical and surrounded by a phospholipids membrane (129) separating two crystalline protein layers (130,131) composed of the PHA polymerases (132), the intracellular PHA depolymerase (133), amphipathic phasing proteins (117,134), PHAspecific regulator proteins (135)(136)(137) and additional proteins with unknown function ( Figure 5) (128). Granules membrane coat is about 2 nm thick, containing 0.5% lipid and 2% protein, of the granule weight (138).…”

Poly(3-hydroxybutyrate-co-3- hydroxyvalerate) nanoparticles prepared by a miniemulsion/solvent evaporation technique: effect of phbv molar mass and concentration

“…Nanoparticles made from natural polymers are interesting drug delivery systems due to their characteristics of biodegradability and biocompatibility [Pich et al, 2006;Reis et al, 2006;Poletto et al, 2008]. PHBV belongs to the group of polyhydroxyalkanoates (PHAs), polyesters naturally synthesized by microorganisms and deposited intracellularly as insoluble spherical inclusions [Grage et al, 2009]. Its characteristics of biocompatibility and biodegradability make PHBV attractive for numerous applications in medicine, including drug delivery systems [Reis et al, 2006;Poletto et al, 2008;Grage et al, 2009;Franceschi et al, 2008;Gangrade and Price, 1991;Sendil et al, 1999].…”

EVALUATION OF POLYHYDROXYALKANOATES PRODUCING BACTERIA ISOLATED FROM SOILS WITH WASTES OF Cocos nucifera

“…Bacteria produce and accumulate PHAs under unbalanced growth conditions, for instance, in the presence of high concentrations of the carbon source and limitation of some other essential nutrient, such as nitrogen, oxygen, phosphorous and magnesium (Verlinden 2007). They are stored in granules within the cell, and their main function is as a reserve of nutrients and energy (Kichise et al 2002, Pötter et al 2002, Grage et al 2009). The PHAs can be produced from renewable resources (Lee 1996, Steinbüchel andHein 2001), but given the high cost of substrates and the processes for the production of PHAs at an industrial level, it is still critical to reduce the expensive costs (Choi and Lee 1997).…”