Specific identification of (R)-3-hydroxyacyl-ACP: CoA transacylase gene from Pseudomonas and Burkholderia strains by polymerase chain reaction.

Polyhydroxyalkanoates (PHA) were biodegradable thermoplastics. Due to their broad applications, direct biosynthesis of PHA from inexpensive substrates, such as carbohydrates, is actively pursued. It has been recently revealed that (R)-3-hydroxyacyl-ACP: CoA transacylase (PhaG) played an important role in this pathway. In this study, a polymerase chain reaction (PCR) protocol was developed for the rapid and specific identification of phaG gene from various bacteria. Using the PCR strategy, the complete open reading frames of two phaG genes from Pseudomonas stutzeri 1317 and Pseudomonas nitroreducens 0802 were cloned from the genomic DNA and functionally expressed in Pseudomonas putida PHAGN-21. Furthermore, this strategy was successful applied in non-Pseudomonas strains, such as Burkholderia. These results suggest that PhaG-mediated pathway of medium-chain-length polyhydroxyalkanoates was widespread among bacteria.

Effects of crystallization of polyhydroxyalkanoate blend on surface physicochemical properties and interactions with rabbit articular cartilage chondrocytes.

As a new member of polyhydroxyalkanoate (PHA) family, poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) has better mechanical properties compared with poly(3-hydroxybutyrate) (PHB). Still, many properties of PHBHHx and its blend with PHB may be exploited for a wide range of applications, such as tissue engineering and drug delivery. In this study, PHBHHx was found to be completely miscible with PHB in their blends. Crystallization behavior of these polyester blends played an important role in determination of the surface physicochemical properties including surface free energy, chemical states and polarity, and could subsequently govern the cellular responses. Interaction between PHB and PHBHHx influenced the non-dispersion surface free energy component, which governed the total surface free energy. It was shown that the blend with a 1:1 ratio of PHB/PHBHHx possessed the highest surface free energy, which was the most optimal material for chondrocytes adhesion. After 24 h, the amount of chondrocytes adhered on films of PHB/PHBHHx (1:1) was 2.1 x 10(4)cells/cm(2), 5-times more compared with that on the PHB films (0.4 x 10(4)cells/cm(2)). The polarity of the blends increased with decreasing crystallinity. After 8 days of cultivation, the chondrocytes attached on PHB films were surrounded by both collagen II and collagen X, the amount of extracellular collagen X decreased with increasing polarity contributed by increasing PHBHHx content in the blend, while chondrocytes changed shapes from spherical to flat with increasing polarity. It indicated that endochondral ossification of chondrocytes was remarkably influenced by the crystallinity of the polyesters.