Polyhydroxyalkanoates (PHAs), are polyesters of 3-, 4- 5- and 6-hydroxyalkanoic acids, produced by a variety of bacterial species under nutrient-limiting conditions with excess carbon. PHA production by Bacillus cereus SPV and Pseudomonas sp. has been explored under different nutrient limiting conditions. Bacillus cereus SPV has been found to produce maximum PHA under nitrogen limiting conditions. Interestingly P(3HB-co-3HV) production was obtained using glucose under potassium-limiting conditions. The Pseudomonas sp. have also been found to utilise a range of different carbon sources including structurally related fatty acids and structurally unrelated carbohydrates. Mcl-PHAs produced include P(3HO), P3(HHX-co-HO-co-HD) and the previously unknown novel mcl-PHA, P(3HO-co-2HDD).
The PHAs produced have been used for the production of tissue engineering scaffolds and drug delivery structures with and without Bioglass®. The microstructure, bioactivity and drug release kinetics have been studied. PHA composites with micro-sized bioactive glass (m-BG) have been compared to composites with nano-sized bioactive glass (n-BG). The incorporation of n-BG particles had a significant reinforcing effect on the composite due to enhancement of the elastic modulus as a function of the n-BG content.