Polyhydroxybutyrate Blends Research Articles

Application of Microbial Polyesters-Polyhydroxyalkanoates as Tissue Engineering Materials

Poly(hydroxybutyrate-co-hydroxyhexanoate) (PHBHHx) has improved mechanical properties over the existing PHA and our results have shown that PHBHHx has better biocompatibility over polyhydroxybutyrate (PHB) and polylactic acid (PLA). Surface treatment with lipases dramatically changed the material surface properties and increased the biocompatibility of the PHBHHx. PHBHHx and its PHB blends had been used to make three dimensional structures and it has been found that cartilage, osteoblast, and fibroblasts all showed strong growth on the PHBHHx scaffolds. The growth was much better compared with PLA. The molecular studies also showed that mRNA encoding cartilages were strongly expressed when cartilage cells were grown on the PHBHHx. As PHBHHx has strong mechanical properties, easily processible and biodegradable, this material can be used to develop a new class of tissue engineering materials.

Fiber Formation in Medium and Ultra‐High‐Molecular‐Weight Polyhydroxybutyrate Blends under Shear Flow

AbstractSummary: Polyhydroxybutyrate (PHB) is an ideal bioplastic, however, this polymer undergoes a severe embrittlement process because of its spherulitic structure, rendering the material brittle. Using a series of in‐situ rheo techniques, we have previously observed only the rapid initial stage of shish formation, we term a partial shish, which existed at high shears in medium‐molecular‐weight PHB, $\overline M _{\rm w}$ = 360 000. The shish kebab morphology is anticipated to remove or severely lessen this embrittlement process whilst providing new properties and applications. For medium and ultra high‐molecular‐weight (MMWT, $\overline M _{\rm w}$ = 360 000/UHMWT, $\overline M _{\rm w}$ = 5 × 106) PHB 99/1 and 99.5/0.5 blends only a partial shish is identified. However, the initial shish formation stage and subsequent stages were observed at 98/2 and 97/3 blend ratios resulting in a complete shish, we term the full shish, and fiber formation was evident. We believe this fiber morphology achieved by high molecular weights is crucial to sustaining the shish kebab structure for an excessive period.Left: In‐situ rheo‐light scattering micrograph; 97/3 MMWT/UHMWT PHB at 100 s−1 for 1 s shear shish held at 75 s. Right: In situ rheo‐optical micrograph; PHB fiber morphology observed at 50 s−1 for 2 s shear 98/2 MMWT/UHMWT PHB after 1 min.imageLeft: In‐situ rheo‐light scattering micrograph; 97/3 MMWT/UHMWT PHB at 100 s−1 for 1 s shear shish held at 75 s. Right: In situ rheo‐optical micrograph; PHB fiber morphology observed at 50 s−1 for 2 s shear 98/2 MMWT/UHMWT PHB after 1 min.

In vivo blending of medium chain length polyhydroxy-alkanoates and polyhydroxybutyrate using recombinant Pseudomonas putida harboring phbCAB operon of Ralstonia eutropha

The in vivo blending of medium chain length polyhydroxyalkanoates (mcl-PHA) and polyhydroxybutyrate (PHB) was carried out using recombinant Pseudomonas putida after transforming the phbCAB operon of Ralstonia eutropha. The most suitable carbon sources for the production of mcl-PHA and PHB blends were identified to be octanoate and gluconate. The molar fractions of 3-hydroxyoctanoate and 3-hydroxybutyrate in the polymer blends were effectively modulated by controlling the mixing ratio of octanoate and gluconate, thereby producing a composition ranging from 95% mcl-PHA to 78% PHB.

Mechanical properties of polyhydroxybutyrate-hydroxybutyrate-hydroxyvalerate copolymer blends

Blends of polyhydroxybutyrate and its copolymers with hydroxyvalerate have been prepared. Under certain conditions of composition and temperature these blends can phase separate. It is shown that for freshly prepared samples, crystallization from a biphasic, rather than a homogeneous, melt leads to improvement in yield and fracture properties. However, during storage at room temperature, an ageing process occurs and the improvement in properties is largely lost.