materials such as absorbable sutures. Properties Water-insoluble and relatively resistant to hydrolytic degradation. This differentiates PHB from most other currently available biodegradable plastics, which are either water-soluble or moisture-sensitive. Good oxygen permeability. Good ultra-violet resistance but poor resistance to acids and bases. Soluble in chloroform and other chlorinated hydrocarbons. Biocompatible and hence is suitable for medical applications. Melting point 175 °C., and glass transition temperature 2 °C. Tensile strength 40 MPa, close to that of polypropylene. Sinks in water (while polypropylene floats), facilitating its anaerobic biodegradation in sediments. Nontoxic. Less 'sticky' when melted. History Polyhydroxybutyrate was first isolated and characterized in 1925 by French microbiologist Maurice Lemoigne. Biodegradation Firmicutes and proteobacteria can degrade PHB. Bacillus, Pseudomonas and Streptomyces species can degrade PHB. Pseudomonas lemoigne, Comamonas sp. Acidovorax faecalis, Aspergillus fumigatus and Variovorax paradoxus are soil microbes capable of degradation. Alcaligenes faecalis, Pseudomonas, and Illyobacter delafieldi, are obtained from anaerobic sludge. Comamonas testosteroni and Pseudomonas stutzeri were obtained from sea water. Few of these are capable of degrading at higher temperatures; notably excepting thermophilic Streptomyces sp. and a thermophilic strain of Aspergillus sp. References External links Abstract of award for PHAs Polyesters Biodegradable plastics Thermoplastics Bioplastics