Poly(3-Hydroxybutyrate), P(3HB) production and its biomedical applications

In this project enhancement of poly(3-hydroxybutyrate), P(3HB) production using a Gram positive bacteria, Bacillus cereus SPV and sucrose as the main carbon source was successfully achieved. Different modes of fermentation including shaken flask, batch, fedbatch and two-stage fermentation were investigated in the study. A modified G-medium was formulated and used throughout the study. Potassium and sulphate were identified as the main limiting factor for P(3HB) accumulation in Bacillus cereus SPV. By limiting the potassium phosphate concentration to 0.5 g/L K2HPO4 in the production medium, the dry cell weight, P(3HB) yield and P(3HB) concentration improved to, 7.21 g/L, 82 % dcw and 5.95 g/L respectively (i.e. 236, 115.8 and 830 % increase in dry cell weight, P(3HB) yield and P(3HB) concentration respectively). In addition, economic production of P(3HB) using agricultural/industrial waste (molasses) as the main carbon substrate was achieved. The study was also carried out in both shaken flask and 2L fermenter. The maximum P(3HB) yield achieved was 61.07 % dcw in 1L shaken flask and 51.37 % dcw in 2L fermenter.

A novel wet cell PHA extraction was successfully developed in this project leading to high purity of the PHA produced with reduced crystallinity and efficient recovery. This is expected to save time, cost and enhanced continuous PHA production.

Furthermore, a novel inexpensive and sustainable ‘compression moulding/particulate leaching’ technique for tissue engineering scaffold fabrication was developed. The novel technique enabled the production of biodegradable composite scaffolds of P(3HB)/microfibrillated cellulose and magnetic P(3HB) nanocomposite for possible applications in cartilage and bone tissue engineering, respectively. Detailed studies on the 2D and 3D composites showed that the inclusion of microfibrillated cellulose into the P(3HB) matrix enhanced the mechanical properties, hydrophilicity, introduced microtopography features, enhanced surface chemistry and biocompatibility of the composite material while inclusion of magnetic nanoparticles and ferrofluid, in addition to the above features added magnetic properties and microhardness to the composite materials.

A unique controlled drug delivery system was developed with potential application in multiple drug delivery. The release study confirmed that the delivery system was able to control the release of BSA, a model protein.

Finally, composite magnetic microspheres were also produced and characterised for their efficient use in the delivery of cancer drug and analyses performed showed that the composite constructs have superparamagnetic properties which would be useful for targeted delivery.