PHB degrading bacteria

The exoeellular enzymes produced by three different polyester-degrading bacteria have been characterized using native granules of PHB as the substrate. The bacteria studied were the following (1) two Pseudomonas strains which... 

Qiua Z, Ikeharab T, Nishi T (2003) Melting behaviour of poly(butylene succinate) in miscible blends with poly(ethylene oxide). Polymer 44 3095-3099 Romen F, Reinhardt S, Jendrossek D (2(X)4) Thermotolerant poly(3-hydioxybutyrate)- degrading bacteria from hot compost and characterization of the PHB depolymerase of Schlegelella sp. KB la. Arch Microbiol 182 157-164... 

Hence, PGA fibers that are sensitive to moisture are one example of material absorbed by hydrolysis with resulting glycoUc acid monomers that are eliminated from the body by biological fluids. Eurthermore, PHB is produced by a wide variety of bacteria. In a reversible way, PHB degrades slowly at physiological temperatures and the metabolites are secreted in urine. Slow degradation rate and continuous elimination of the PHB avoid the formation of acidic debris, which can cause inflammation. 

In nature, there are several sources of enzymes that are capable of catalysing the hydrolysis of PHB. The polymer itself is produced by bacteria and occurs in cells as discrete inclusion bodies. These bodies contain the necessary enzymes for degrading the polymer, preventing its build-up in the cell. As well as this, there are numerous bacteria and fungi, many of which are found in the soil, that are capable of secreting the necessary enzymes outside their cell walls, and thus of iiufiating degradation of PHB. 

Poly(hydroxyalkanoates) (PHAs), of which poly(hydroxybutyrate) (PHB) is the most common, can be accumulated by a large number of bacteria as energy and carbon reserve. Due to their bio degradability and bio compatibility these optically active biopolyesters may find industrial applications. A general overview of the physical and material properties of PHAs, alongside with accomplished applications and new developments in this field is presented in this chapter. 

We have recently reported the development of a process for the in vivo depolymerization of PHA in several natural PHA producing bacteria including A. latus, R. eutropha, and pseudomonads (15). Metabolic pathways involved in the synthesis and degradation of PHB are shown in Fig. 1. 

From a medical point of view, it should be noted that a healthy human tissue does not contain bacteria utilizing PHB. But experiments [23] have suggested a difference between the rate of hydrolytic degradation in vivo and in vitro. The interpretation is that enzymes from the body itself catalyze the hydrolytic degradation process in vivo. During the degradation, PHB molecules decompose into 3HB. It is found in human blood and can be metabolized by the body. 

The enzymatic hydrolysis of poly-p-hydroxybutyrate, PHB, by several different bacteria, which are known to secrete active esterases, has been studied in some detail by several research groups [7, 8]. As with the polysaccharides, the final products of these degradation reactions are the monomers, dimers and trimers, which are removed by hydrolysis only from hydroxyl-end of the polymer chain, as follows ... 

Biodegradable, aliphatic polyesters can be synthesized or produced by bacteria and cyanobacteria. These organisms accumulate poly(3-hydroxy butyrate) (PHB) up to 80 wt% of the dry cellular material. Long branching has been produced by modifying the culture medium [Ramsay et ah, 1991]. PHB is degraded by the enzyme poly(3-hydroxybutyrate depolymerase). 

PHB biodegradation in the enriched culture obtained from soil on the medium used to cultivate denitrifying bacteria (Gil tai medium) has also been studied. The dominant bacterial species. Pseudomonas fluorescens and Pseudomonas stutzeri, have been identified in this enrichment culture. Under denitrifying conditions, PHB films were completely degraded for 7 days. Both the film weight and of PHB decreased with time. In... 

Poly(3-hydroxybutyrate) (PHB) is crystalline, thermoplastic polyester made by micro-organisms as an energy storage molecule (Structure 9). As such, it can be enzymatically degraded by certain bacteria. It is often copolymerized with hydroxyvaleric acid (Structure 10) to create poly(3-hydroxybutyrate-co-3-hydroxyvalerate), P(HB-co-HV). Solvent casting has been described from solution in chloroform, methylene chloride, and tetrahydrofuran [59,60]. 

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