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Pseudomonas oleovorans as a source of bioplastics: production and characterization of poly(3-hydroxyalkanoates)

Poly(3-hydroxyalkanoates) WAS) are biological polyesters which are accumulated by a wide range of bacteria under conditions of excess carbon source and limiting concentrations of an essential nutrient such as nitrogen. Poly(3-hydroxybutyrate) (PHB), the best known example of these biopolymers has been extensively studied since its discovery in 1926. Only recently, it has been considered as a possible biodegradable substitute for conventional nondegradable plastics. PHI3 has long been thought the only bacterial polyester, until in the early 1980's a PHB resembling polymer was discovered in Pseudomom oleovorans after growth on n-octane. The P. oleovorans PHA distinguished itself from PHB by having longer pendant groups attached to a similar backbone. Moreover, it was found that the length of the pendant group was dependent on the carbon source used to grow the organism. Thus, the PHA-synthesizing system of P. oleovorans can be used to produce a range of PHAs. To be commercially interesting in the future, this novel class of polymers has to satisfy two important conditions: 1. besides the expected biodegradable properties, the physical and mechanical properties of any of the PHAs must be promising, and 2. PHAs must be available in large quantities. In this respect, we have examined some physical properties of a number of PHAs isolated from P. oleovorans and studied the production of one of them (the 'octane-derived' polymer) in fed-batch and continuous culture systems.